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253 Cards in this Set
- Front
- Back
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Histology (Microscopic anatomy)
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Study of tissues & how they are arranged into organs, also known as Microscopic anatomy.
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Cytology
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Study of cell structure
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Tissue
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A group of similar cells & cell products that arise from same region of embryo & work together to preform a specific structural or physiological role in a organ
•four broad categories of tissues –epithelial tissue –connective tissue –nervous tissue –muscular tissue |
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Epithelium
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•consists of a flat sheet of closely adhering cells
•one or more cells thick •upper surface usually exposed to the environment or an internal space in the body •covers body surface •lines body cavities •forms the external and internal linings of many organs •constitutes most glands •extracellular material is so thin it is not visible with a light microscope •epithelia allows no room for blood vessels •lie on a layer of loose connective tissue and depend on its blood vessels for nourishment and waste removal |
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Epithelium tissues
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Composed of layers. Of closely spaced cells that cover organ surfaces from glands & serve for protection, secretion & absorption.
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Epithelium tissues
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cells that cover organ surfaces from glands & serve for protection, secretion & absorption.
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Simple Epithelia
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–contains one layer of cells
–named by shape of cells –all cells touch the basement membrane |
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Stratified Epithelia
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– contains more than one layer
– named by shape of apical cells – some cells rest on top of others and do not touch basement membrane |
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Four types of simple epithelia
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•three named for their cell shapes
–simple squamous (thin scaly cells) –simple cuboidal (square or round cells) –simple columnar (tall narrow cells) •fourth type – –pseudostratified columnar •not all cells reach the free surface •shorter cells are covered over by taller ones •looks stratified •every cell reaches the basement membrane •goblet cells – wineglass-shaped mucus secreting cells in simple columnar and pseudostratified epithelia |
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simple squamous epithelia
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•single row of thin cells
•permits rapid diffusion or transport of substances •secretes serous fluid •alveoli, glomeruli, endothelium, and serosa |
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simple squamous epithelia
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simple cuboidal epithelial
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•single layer of square or round cells
•absorption and secretion, mucus production and movement •liver, thyroid, mammary and salivary glands, bronchioles, and kidney tubules |
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simple cuboidal epithelial
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•single layer of square or round cells
•absorption and secretion, mucus production and movement •liver, thyroid, mammary and salivary glands, bronchioles, and kidney tubules |
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Classes of epithelial & shapes
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Classes: Simple, pseudostratified columnar & stratified
2nd row shapes: squamous, cuboidal & columnar |
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Simple vs. Stratified Epithelia
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•Simple epithelium
–contains one layer of cells –named by shape of cells –all cells touch the basement membrane • Stratified epithelium – contains more than one layer – named by shape of apical cells – some cells rest on top of others and do not touch basement membrane |
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Simple Columnar Epithelium
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•single row tall, narrow cells
–oval nuclei in basal half of cell –brush border of microvilli, ciliated in some organs, may possess goblet cells •absorption and secretion; mucus secretion •lining of GI tract, uterus, kidney and uterine tubes |
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Simple Columnar Epithelium
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pseudostratified columnar epithelium
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•looks multilayered; some not reaching free surface; all touch basement membrane
–nuclei at several layers –with cilia and goblet cells •secretes and propels mucus •respiratory tract and portions of male urethra |
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pseudostratified columnar epithelium
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Stratified Epithelia
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•range from 2 to 20 or more layers of cells
•some cells resting directly on others •only the deepest layer attaches to the basement membrane. •three stratified epithelia are named for the shapes of their surface cells –stratified squamous -stratified cuboidal –stratified columnar (rare) •fourth type –transitional epithelium •most widespread epithelium in the body •deepest layers undergo continuous mitosis –their daughter cells push toward the surface and become flatter as they migrate farther upward –finally die and flake off – exfoliation or desquamation •two kinds of stratified squamous epithelia –keratinized – found on skin surface, abrasion resistant –nonkeratinized – lacks surface layer of dead cells |
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2 kinds Stratified squamous Epithelia
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-keratinized – found on skin surface, abrasion resistant
–nonkeratinized – lacks surface layer of dead cells |
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Stratified squamous Epithelia
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stratified cuboidal Epithelium
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stratified columnar (rare)
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nonkeratinized stratified squamous epithelium
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Keratinized vs non-Keratinized
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Keratinized tissue like the skin has lots of vessicles containing keratohyaline, a protein that eventually turns into keratine when the cell dies, providing that epithelium with protection and resistance to traction and friction, and it makes it impermeable. The only epithelium that keratinizes is stratified squamous, and it only happens in the skin (in normal conditions).
Non keratinized tissue does not offer as much protection and allows the diffusion of materials through the cell junctions and the cell's body. |
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keratinized stratified squamous epithelia
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•multiple cell layers with cells becoming flat and scaly toward surface
•epidermis; palms and soles heavily keratinized •resists abrasion; retards water loss through skin; resists penetration by pathogenic organisms |
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nonkeratinized stratified squamous epithelia
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•same as keratinized epithelium without the surface layer of dead cells
•tongue, oral mucosa, esophagus and vagina •resists abrasion and penetration of pathogens |
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stratified cuboidal epithelium
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•two or more cell layers; surface cells square or round
•secretes sweat; sperm production and produces ovarian hormones •sweat gland ducts; ovarian follicles and seminiferous tubules |
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Transitional epithelium
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•multilayered epithelium surface cells that change from round to flat when stretched
•allows for filling of urinary tract •ureter and bladder |
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Connective Tissue
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•connective tissue – a type of tissue in which cells usually occupy less space than the extracellular material
•binds organs to each other •support and protect organs •most cells of connective tissue are not in direct contact with each other –separated by extracellular material •highly vascular – richly supplied with blood vessels •most abundant, widely distributed, and histologically variable of the primary tissues |
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Functions of Connective Tissue
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•binding of organs – tendons and ligaments
•support – bones and cartilage •physical protection – cranium, ribs, sternum •immune protection – white blood cells attack foreign invaders •movement – bones provide lever system •storage – fat, calcium, phosphorus •heat production – metabolism of brown fat in infants •transport - blood |
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Components of Fibrous Connective Tissue
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•cells
–fibroblasts produce fibers and ground substance –macrophages phagocytize foreign material and activate immune system when sense foreign matter (antigen) •arise from white blood cell - monocytes –leukocytes or white blood cells •neutrophils wander in search of and attacking bacteria •lymphocytes react against bacteria, toxins, and other foreign material –plasma cells synthesize disease fighting antibodies •arise from lymphocytes –mast cells – found along side of blood vessels •secrete heparin inhibits clotting •histamine that dilates blood vessels –adipocytes store triglycerides (fat molecules) |
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Components of Fibrous Connective Tissue
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•fibers
–collagenous fibers •most abundant of the body’s proteins – 25% •tough, flexible, and resist stretching •tendons, ligaments, and deep layer of the skin are mostly collagen •less visible in matrix of cartilage and bone –reticular fibers •thin collagen fibers coated with glycoprotein •form framework of such organs as spleen and lymph nodes –elastic fibers •thinner than collagenous fibers •branch and rejoin each other •made of protein called elastin •allows stretch and recoil •yellow fibers – fresh elastic fibers |
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Components of Fibrous Connective Tissue
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•ground substance
–usually a gelatinous to rubbery consistency resulting from three classes of large molecules –glycosaminoglycans (GAG) •long polysaccharide composed of unusual disaccharides called amino sugars and uronic acid •play important role of regulating water and electrolyte balance in the tissues •chondroitin sulfate – most abundant GAG –in blood vessels and bone –responsible for stiffness of cartilage •hyaluronic acid – viscous, slippery substance that forms an effective lubricant in joints and constitutes much of the vitreous body of the eyeball –proteoglycan •gigantic molecule shaped like a test-tube brush •forms thick colloids that creates strong structural bond between cells and extracellular macromolecules – holds tissues together –adhesive glycoproteins – bind components of tissues together |
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Types of Fibrous Connective Tissue
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•loose connective tissue
–much gel-like ground substance between cells –types •areolar •reticular •dense connective tissue –fibers fill spaces between cells –types vary in fiber orientation •dense regular connective tissue •dense irregular connective tissue |
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Areolar Tissue
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•loosely organized fibers, abundant blood vessels, and a lot of seemingly empty space
•underlies all epithelia, in serous membranes, between muscles, passageways for nerves and blood vessels |
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Areolar Tissue
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•loosely organized fibers, abundant blood vessels, and a lot of seemingly empty space
•possess all six cell types •fibers run in random directions –mostly collagenous, but elastic and reticular also present •found in tissue sections from almost every part of the body –surrounds blood vessels and nerves •nearly every epithelium rests on a layer of areolar tissue –blood vessels provide nutrition to epithelium and waste removal –ready supply of infection fighting leukocytes that move about freely in areolar tissue |
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Reticular tissue
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•mesh of reticular fibers and fibroblasts
•forms supportive stroma (framework) for lymphatic organs •found in lymph nodes, spleen, thymus and bone marrow |
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Dense irregular connective tissue
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•densely, packed, parallel collagen fibers
–compressed fibroblast nuclei •tendons attach muscles to bones and ligaments hold bones together |
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Transitional epithelium
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Connective Tissue
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Areolar Tissue
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Dense irregular connective tissue
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Dense regular connective tissue
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Reticular connective tissue
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Areolar Tissue
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Reticular connective tissue
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Adipose Tissue
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•empty-looking cells with thin margins; nucleus pressed against cell membrane
•energy storage, insulation, cushioning –subcutaneous fat and organ packing –brown fat (hibernating animals) produces heat |
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Adipose Tissue
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•adipose tissue (fat) – tissue in which adipocytes are the dominant cell type
•space between adipocytes is occupied by areolar tissue, reticular tissue, and blood capillaries •fat is the body’s primary energy reservoir •the quantity of stored triglyceride and the number of adipocytes are quite stable in a person –fat is recycled continuously to prevent stagnation –new triglycerides are constantly synthesized and stored –old triglycerides are hydrolyzed and released into circulation •provides thermal insulation •anchors and cushions organs such as eyeball, kidneys •contributes to body contours – female breast and hips •on average, women have more fat than men •too little fat can reduce female fertility •most adult fat is called white fat |
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Adipose Tissue
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Cartilage
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•supportive connective tissue with flexible, rubbery matrix
•gives shape to ear, tip of nose, and larynx •chondroblasts produce matrix and surround them selves until they become trapped in little cavities (lacunae) •chondrocytes – cartilage cells in lacunae •perichondrium – sheath of dense irregular connective tissue that surrounds elastic and most hyaline cartilage (not articular cartilage) –contains a reserve population of chondroblasts that contribute to cartilage growth throughout life •No blood vessels –diffusion brings nutrients and removes wastes –heals slowly •matrix rich in chondroitin sulfate and contain collagen fibers •types of cartilage vary with fiber types –hyaline cartilage, fibrocartilage and elastic cartilage |
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hyaline cartilage
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•clear, glassy microscopic appearance because of unusual
fineness of the collagen fibers •usually covered by perichondrium •articular cartilage, costal cartilage, trachea, larynx, fetal skeleton •eases joint movement, holds airway open, moves vocal cords during speech |
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Hyaline cartilage
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Elastic cartilage
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•cartilage containing elastic fibers
•covered with perichondrium •provides flexible, elastic support –external ear and epiglottis |
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Elastic cartilage
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Fibrocartilage
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Fibrocartilage
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•cartilage containing large, coarse bundles of collagen fibers
•never has perichondrium •resists compression and absorbs shock –pubic symphysis, menisci, and intervertebral discs |
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bone
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–an organ of the body; femur, mandible; composed of multiple tissue types
–bone tissue – osseous tissue – makes up most of the mass of bone |
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Bone
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•two forms of osseous tissue
–spongy bone - spongy in appearance •delicate struts of bone - trabeculae •covered by compact bone •found in heads of long bones and in middle of flat bones such as the sternum –compact bone – denser calcified tissue with no visible spaces •more complex arrangement •cells and matrix surround vertically oriented blood vessels in long bones |
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Bone Tissue (compact bone)
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•most compact bone is arranged in cylinders that surround central (haversian or osteonic) canals that run longitudinally through shafts of long bones
–blood vessels and nerves travel through central canal •bone matrix deposited in concentric lamella –onionlike layers around each central canal •osteon – central canal and its surrounding lamellae •osteocytes – mature bone cells that occupy the lacunae •canaliculi – delicate canals that radiate from each lacuna to its neighbors, and allows osteocytes to contact each other •periosteum – tough fibrous connective tissue covering of the bone as a whole |
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Blood
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•Fluid connective tissue
•Transports cells & dissolved matter from place to place •Plasma-blood's liquid ground substance •formed elements – cells and cell fragments –erythrocytes – red blood cells – transport O2 and CO2 –leukocytes – white blood cells – defense against infection and other diseases –platelets – cell fragments involved in clotting and other mechanisms |
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Nervous tissue
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Specialized for communication by electrical & chemical signals
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Nerve cells
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•consists of neurons (nerve cells) –
–detect stimuli –respond quickly –transmit coded information rapidly to other cells •and neuroglia (glial) –protect and assist neurons –‘housekeepers’ of nervous system •neuron parts –neurosoma (cell body) •houses nucleus and other organelles •cell’s center of genetic control and protein synthesis –dendrites •multiple short, branched processes •receive signals from other cells •transmit messages to neurosoma –axon (nerve fiber) |
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Neuron parts
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•neuron parts
–neurosoma (cell body) •houses nucleus and other organelles •cell’s center of genetic control and protein synthesis –dendrites •multiple short, branched processes •receive signals from other cells •transmit messages to neurosoma –axon (nerve fiber) |
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erythrocytes
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red blood cells – transport O2 and CO2
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leukocytes
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white blood cells – defense against infection and other diseases
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platelets
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– cell fragments involved in clotting and other mechanisms
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osteon (in bone)
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central canal and its surrounding lamellae
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osteocytes (in bone)
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mature bone cells that occupy the lacunae
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canaliculi (in bone)
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– delicate canals that radiate from each lacuna to its neighbors, and allows osteocytes to contact each other
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periosteum
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tough fibrous connective tissue covering of the bone as a whole
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neuron parts
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Nerve cells
–neurosoma (cell body) •houses nucleus and other organelles •cell’s center of genetic control and protein synthesis –dendrites •multiple short, branched processes •receive signals from other cells •transmit messages to neurosoma |
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neurosoma (cell body)
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neuron parts
•houses nucleus and other organelles •cell’s center of genetic control and protein synthesis |
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dendrites
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neuron parts
•multiple short, branched processes •receive signals from other cells •transmit messages to neurosoma |
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neuroglia (glial)
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–protect and assist neurons
–‘housekeepers’ of nervous system |
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Muscular Tissue
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elongated cells that are specialized to contract in response to stimulation
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Muscular Tissue function
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•primary job is to exert physical force on other tissues and organs
•creates movements involved in body and limb movement, digestion, waste elimination, breathing, speech, and blood circulation •important source of body heat |
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Types of Muscular Tissue
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three types of muscle: skeletal, cardiac, and smooth
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Skeletal Muscular Tissue
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Long, thread like muscle fibers
Most attached to bone Exceptions- tongue, facial muscles, upper esophagus & some sphincter muscle Multi nuclei adjacent to plasma membrane Striations-alt light & dark bands Voluntary-conscious over skeletal muscles |
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Cardiac muscle tissue
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Skeletal Muscular Tissue
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Bone tissue
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Blood cells
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Neuron cell
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fibrocartilage
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elastic cartilage
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hyaline cartilage
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cardiac muscle
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Limit to heart
Myocytes or cardiocytes are much shorter, branched & notched at ends Contains one centrally located nucleus surrounded by light staining glycogen Intercalated disc joined cardiocytes end to end -provide electric &mechanical connection Striated & involuntary |
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Smooth muscle
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•lacks striations and is involuntary
•relatively short, fusiform cells (thick in middle, tapered at ends) •one centrally located nucleus •visceral muscle – forms layers of digestive, respiratory, and urinary tract: blood vessels, uterus and other viscera •propels contents through an organ, regulates diameter of blood vessels |
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Smooth muscle
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Smooth muscle
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Cardiac, skeletal & smooth muscle
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Intercellular Junctions
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-connections between one cell and another
•all cells (except blood and metastatic cancer cells) are anchored to each other or their matrix by intercellular junctions •resist stress and communicate with each other |
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Intercellular Junctions
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Tight Junctions
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A region in which adjacent cells are bound together by fusion of the outer phospholipid layer of their plasma membranes.
–in epithelia, forms a zone that complete encircles each cell near its apical pole –seals off intercellular space –makes it impossible for something to pass between cells |
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Desmosomes
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patch that holds cells together (like a clothing snap)
•serves to keep cells from pulling apart – resists mechanical stress •hooklike J-shaped proteins arise from cytoskeleton –approach cells surface –penetrate into thick protein plaques linked to transmembrane proteins •hemidesmosomes – anchor the basal cells of epithelium to the underlying basement membrane –epithelium can not easily peel away from underlying tissues |
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Gap Junctions
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formed by a ringlike connexon
–consists of six transmembrane proteins arranged like segments of an orange –surrounding a water-filled pores –ions, glucose, amino acids and other solutes pass from one cell to the next |
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Tight junction
Desmosome Gap junction |
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Endocrine and Exocrine Glands
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•gland – cell or organ that secrete substances for use elsewhere in the body or releases them for elimination from the body
–composed of epithelial tissue in a connective tissue framework and capsule •exocrine glands - maintain their contact with the body surface by way of a duct (epithelial tube that conveys secretion to surface) –sweat, mammary and tear glands •endocrine glands - lose their contact with the surface and have no ducts –hormones – secretion of endocrine glands –secrete (hormones) directly into blood –thyroid, adrenal and pituitary glands •some organs have both endocrine and exocrine function –liver, gonads, pancreas •unicellular glands – found in epithelium that is predominantly nonsecretory –can be endocrine or exocrine –mucus-secreting goblet or endocrine cells of stomach and small intestine |
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maintain their contact with the body surface by way of a duct (epithelial tube that conveys secretion to surface)
–sweat, mammary and tear glands |
exocrine glands
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lose their contact with the surface and have no ducts
–hormones – secretion of endocrine glands –secrete (hormones) directly into blood –thyroid, adrenal and pituitary glands |
endocrine glands
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Exocrine Gland Structure
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•capsule – connective covering of most glands
–septa or trabeculae – extensions of capsule that divide the interior of the gland into compartments (lobes) –further divided into smaller lobules •stroma – connective tissue framework of the gland –supports and organizes glandular tissue •parenchyma – the cells that perform the tasks of synthesis and secretion –typically cuboidal or simple columnar epithelium |
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Exocrine Gland Structure
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Types of Exocrine Glands
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•simple - unbranched duct
•compound - branched duct •shape of gland –tubular – duct and secretory portion have uniform diameter –acinar - secretory cells form dilated sac (acinus or alveolus) –tubuloacinar - both tubular and acinar portions |
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Types of Exocrine Glands
Compound tubular |
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Types of Secretions
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•serous glands
–produce thin, watery secretions •perspiration, milk, tears and digestive juices •mucous glands –produce glycoprotein, mucin, that absorbs water to form a sticky secretion called mucus –goblet cells – unicellular mucous glands •mixed glands –contain both cell types and produce a mixture of the two types of secretions •cytogenic glands –release whole cells, sperm and egg cells |
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Types of Exocrine Glands
simple |
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Types of Exocrine Glands
compound acinar |
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Types of Exocrine Glands
Compound tubular |
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Methods of Secretion
Merocrine Gland |
have vesicles that release their secretion by exocytosis
–tear glands, pancreas, gastric glands, and others •apocrine glands – primarily merocrine mode of secretion –axillary sweat glands, mammary glands |
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Methods of Secretion
Merocrine Gland |
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Methods of Secretion
Holocrine Gland |
cells accumulate a product and then the entire cell disintegrates
–secretion a mixture of cell fragments and synthesized substance –oil glands of scalp, glands of eyelids |
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Holocrine Gland
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Membranes
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line body cavities and cover their viscera
•cutaneous membrane - the skin – largest membrane in the body –stratified squamous epithelium (epidermis) over connective tissue (dermis) –relatively dry layer serves protective function •mucous membrane (mucosa) – lines passageways open to the external environment •serous membrane (serosa) - internal membrane –simple squamous epithelium over areolar tissue – produces serous fluid that arises from blood –covers organs and lines walls of body cavities •endothelium lines blood vessels and heart •mesothelium line body cavities (pericardium, peritoneum and pleura) •synovial membrane - lines joint cavities –connective tissue layer only, secretes synovial fluid |
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cutaneous membrane -
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the skin – largest membrane in the body
–stratified squamous epithelium (epidermis) over connective tissue (dermis) –relatively dry layer serves protective function |
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mucous membrane (mucosa)
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lines passageways open to the external environment
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•serous membrane (serosa)
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internal membrane
–simple squamous epithelium over areolar tissue – produces serous fluid that arises from blood –covers organs and lines walls of body cavities •endothelium lines blood vessels and heart •mesothelium line body cavities (pericardium, peritoneum and pleura) |
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synovial membrane
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lines joint cavities
–connective tissue layer only, secretes synovial fluid |
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mucous membrane (mucosa)
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•lines passages that open to the external environment
–digestive, respiratory, urinary, and reproductive tracts •consists of two to three layers: –epithelium –lamina propria – areolar connective tissue –muscularis mucosae – smooth muscle layer •absorptive, secretory, and protective functions •covered with mucus |
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mucous membrane (mucosa)
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Tissue Growth
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•tissue growth – increasing the number of cells or the existing cells grow larger
•hyperplasia - tissue growth through cell multiplication •hypertrophy - enlargement of preexisting cells –muscle grow through exercise –accumulation of body fat •neoplasia – development of a tumor (neoplasm) –benign or malignant –composed of abnormal, nonfunctional tissue |
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- tissue growth through cell multiplication
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•hyperplasia
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hypertrophy
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enlargement of preexisting cells
–muscle grow through exercise –accumulation of body fat |
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neoplasia
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development of a tumor (neoplasm)
–benign or malignant –composed of abnormal, nonfunctional tissue |
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Changes in Tissue Types
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•Differentiation
–unspecialized tissues of embryo become specialized mature types •mesenchyme to muscle •Metaplasia –changing from one type of mature tissue to another •simple cuboidal tissue of vagina before puberty changes to stratified squamous after puberty •pseudostratified columnar epithelium of bronchi of smokers to stratified squamous epithelium |
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Differentiation
–unspecialized tissues of embryo become specialized mesenchyme to muscle |
Changes in Tissue Types:Differentiation
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–changing from one type of mature tissue to another
•simple cuboidal tissue of vagina before puberty changes to stratified squamous after puberty •pseudostratified columnar epithelium of bronchi of smokers to stratified squamous epithelium |
Changes in Tissue Types :Metaplasia
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Tissue Repair
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-regeneration
-fibrosis |
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replacement of dead or damaged cells by the same type of cell as before
–restores normal function –skin injuries and liver regenerate |
regeneration (tissue repair)
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- replacement of damaged cells with scar tissue
–holds organs together –does not restore normal function •severe cuts and burns, healing of muscle injuries, scarring of lungs in tuberculosis |
fibrosis (tissue repair)
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Wound Healing 1
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•severed blood vessels bleed into cut
•mast cells and damaged cells release histamine –dilates blood vessels –increases blood flow to area –makes capillaries more permeable •blood plasma seeps into the wound carrying: –antibodies –clotting proteins –blood cells |
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Wound Healing 1
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Blood clot forms in tissue
-loosely knitting edges of cut together -inhibits spread of pathogens from injury site to healthy tissue -forms scab that temp seals wounds & blocks infection -macrophages phagocytize and digest tissue debris |
Wound Healing 2
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Wound Healing 2
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Wound healing 3
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-new capillaries sprout from nearby vessels & grow into wound
-deeper portions become infiltrated by capillaries & fibroblast -transform into soft mass- granulation tissue -macrophages remove blood clot -fibroblasts deposit new collagen -begins 3-4 days after injury and lasts up to 2 weeks |
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Wound healing 3
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Wound healing 4
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Wound healing 4
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-surface epithelium cells around wound x & move into wound area beneath the scab
-Epithelium regenerates -connective tissue undergoes fibrosis -scar tissue may or may not show through epithelium -remodeling (maturation) phase begins several weeks after injury and may last up to 2 yrs |
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Tissue Shrinkage and Death
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•atrophy – shrinkage of a tissue through a loss in cell size or number
–senile atrophy through normal aging –disuse atrophy from lack of use (astronauts) •necrosis – premature, pathological death of tissue due to trauma, toxins, or infections –infarction – sudden death of tissue when blood supply is cut off –gangrene – tissue necrosis due to insufficient blood supply –decubitus ulcer – bed sore or pressure sore •pressure reduces blood flow to an area •a form of dry gangrene –gas gangrene - anaerobic bacterial infection •apoptosis - programmed cell death –normal death of cells that have completed their function and best serve the body by dying and getting out of the way |
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shrinkage of a tissue through a loss in cell size or number
–senile atrophy through normal aging –disuse atrophy from lack of use (astronauts) |
atrophy (tissue shrinkage)
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premature, pathological death of tissue due to trauma, toxins, or infections
–infarction – sudden death of tissue when blood supply is cut off –gangrene – tissue necrosis due to insufficient blood supply –decubitus ulcer – bed sore or pressure sore •pressure reduces blood flow to an area •a form of dry gangrene –gas gangrene - anaerobic bacterial infection |
necrosis (death of tissue)
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programmed cell death
–normal death of cells that have completed their function and best serve the body by dying and getting out of the way |
apoptosis (death of cell)
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Stem Cells
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•stem cells - undifferentiated cells that are not yet performing any specialized function
–have potential to differentiate into one or more types of mature functional cells •developmental plasticity – diversity of mature cell types to which stem cells can give rise •embryonic stem cells –totipotent - have potential to develop into any type of fully differentiated human cell •source - cells of very early embryo –pluripotent – can develop into any type of cell in the embryo •source - cells of inner cell mass of embryo •adult stem cells - undifferentiated cells in tissues of adults –multipotent - bone marrow producing several blood cell types –unipotent – most limited plasticity - only epidermal cells produced |
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Types of stem cells
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•developmental plasticity
•embryonic stem •adult stem cells - undifferentiated cells in tissues of adults |
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stem cells
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undifferentiated cells that are not yet performing any specialized function
–have potential to differentiate into one or more types of mature functional cells |
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developmental plasticity stem cells
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– diversity of mature cell types to which stem cells can give rise
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embryonic stem cells
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–totipotent - have potential to develop into any type of fully differentiated human cell
•source - cells of very early embryo –pluripotent – can develop into any type of cell in the embryo •source - cells of inner cell mass of embryo •Embryonic are more often totipotent. |
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adult stem cells
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undifferentiated cells in tissues of adults
–multipotent - bone marrow producing several blood cell types –unipotent – most limited plasticity - only epidermal cells produced •adult stem cells have limited developmental potential –difficult to harvest and culture |
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Stem Cells
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•Most adult cells have limited number of times they can divide (sometimes 0).
•Most tissues contain a population of stem cells that retain ability to grow. •Often they are relatively undifferentiated and their daughters differentiate into mature tissue cells. •Pluripotent – differentiate into several cell types, not all •Totipotent – can form all cells of the body |
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Stem Cell Therapy
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•possible treatment for diseases caused by loss of functional cell types by embryonic stem cells
–cardiac muscle cells, injured spinal cord, insulin-secreting cells •Embryonic are more often totipotent. •skin and bone marrow stem cells have been used in therapy for years •adult stem cells have limited developmental potential –difficult to harvest and culture |
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- have potential to develop into any type of fully differentiated human cell
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totipotent
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•skin and bone marrow stem cells have been used in therapy for years
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Stem Cell Therapy
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Integumentary System
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– consists of the skin and its accessory organs
–hair, nails, and cutaneous glands |
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Integumentary System
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•most visible system and more attention paid to this organ system
•inspection of the skin, hair, and nails is significant part of a physical exam •skin is the most vulnerable organ –exposed to radiation, trauma, infection, and injurious chemicals •receives more medical treatment than any other organ system •dermatology – scientific study and medical treatment of the integumentary system |
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Skin and Subcutaneous Tissue
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•the body’s largest and heaviest organ
–covers area of 1.5 -2.0 m2 –15 % of body weight •consists of two layers: –epidermis – stratified squamous epithelium –dermis – connective tissue layer •hypodermis – another connective tissue layer below the dermis •most skin is 1 – 2 mm thick •ranges from 0.5 mm on eyelids to 6 mm between shoulder blades •thick skin – on palms and sole, and corresponding surfaces on fingers and toes –has sweat glands, but no hair follicles or sebaceous (oil) glands –epidermis 0.5 mm thick •thin skin – covers rest of the body |
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– another connective tissue layer below the dermis
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hypodermis
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Functions of the Skin
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•resistance to trauma and infection
–keratin –acid mantle •other barrier functions –waterproofing –UV radiation –harmful chemicals •vitamin D synthesis –skin first step –liver and kidneys complete process •sensation –skin is our most extensive sense organ •thermoregulation –thermoreceptors –vasoconstriction / vasodilation •nonverbal communication –acne, birthmark, or scar •transdermal absorption –administration of certain drugs steadily through thin skin – adhesive patches |
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Structure of dermis
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Cell types & layers of dermis
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•epidermis – keratinized stratified squamous epithelium
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–dead cells at the surface packed with tough protein – keratin
–lacks blood vessels –depends on the diffusion of nutrients from underlying connective tissue –sparse nerve endings for touch and pain |
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Cells of Epidermis
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•five types of cells of the epidermis
5 types –stem cells –keratinocytes –melanocytes –tactile (merkel) cells –dendritic (langerhans) cells |
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1 of 5 types of cells of the epidermis
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–stem cells
•undifferentiated cells that give rise to keratinocytes • in deepest layer of epidermis (stratum basale) |
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1 of 5 types of cells of the epidermis
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–keratinocytes
•great majority of epidermal cells •synthesize keratin |
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1 of 5 types of cells of the epidermis
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–melanocytes
•occur only in stratum basale •synthesize pigment melanin that shields DNA from ultraviolet radiation •branched processes that spread among keratinocytes |
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1 of 5 types of cells of the epidermis
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–tactile (merkel) cells
•in basal layer of epidermis •touch receptor cells associated with dermal nerve fibers |
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1 of 5 types of cells of the epidermis
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–dendritic (langerhans) cells
•macrophages originating in bone marrow that guard against pathogens •found in stratum spinosum and granulosum •stand guard against toxins, microbes, and other pathogens that penetrate skin |
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Stratum Basale
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•a single layer of cuboidal to low columnar stem cells and keratinocytes resting on the basement membrane
–melanocytes and tactile cells are scattered among the stem cells and keratinocytes •stem cells of stratum basale divide –give rise to keratinocytes that migrate toward skin surface –replace lost epidermal cells |
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Stratum Spinosum
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•consists of several layers of keratinocytes
•thickest stratum in most skin –in thick skin, exceeded by stratum corneum •deepest cells remain capable of mitosis –cease dividing as they are pushed upward •produce more and more keratin filaments which causes cell to flatten –higher up in this stratum, the flatter the cells appear •dendritic cells found throughout this stratum •named for artificial appearance created in histological section –numerous desmosomes and cell shrinkage produces spiny appearance |
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Stratum Granulosum
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•consists of 3 to 5 layers flat keratinocytes
•contain coarse dark-staining keratohyalin granules |
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Stratum Lucidum
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•seen only in thick skin
•thin translucent zone superficial to stratum granulosum •keratinocytes are densely packed with eleidin •cells have no nucleus or other organelles •zone has a pale, featureless appearance with indistinct boundaries |
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Stratum Corneum
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•up to 30 layers of dead, scaly, keratinized cells
•form durable surface layer –surface cells flake off (exfoliate) •resistant to abrasion, penetration, and water loss |
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Life History of Keratinocytes
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•keratinocytes are produced deep in the epidermis by stem cells in stratum basale
–some deepest keratinocytes in stratum spinosum also multiply and increase their numbers •mitosis requires an abundant supply of oxygen and nutrients –deep cells acquire from blood vessels in nearby dermis –once epidermal cells migrate more than two or three cells away from the dermis, their mitosis ceases •newly formed keratinocytes push the older ones toward the surface |
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Life History of Keratinocytes
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•in 30 - 40 days a keratinocyte makes its way to the skin surface and flakes off
–slower in old age –faster in skin injured or stressed •calluses or corns – thick accumulations of dead keratinocytes on the hands or feet •cytoskeleton proliferates as cells are shoved upward •cells grow flatter •produce lipid-filled membrane-coating vesicles (lamellar granules) •in stratum granulosum three important developments occur –keratinocyte nucleus and other organelles degenerate, cells die –keratohyalin granules release a protein filaggrin •binds the keratin filaments together into coarse, tough bundles –membrane-coating vesicles release lipid mixture that spreads out over cell surface and waterproofs it |
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Epidermal Water Barrier
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•epidermal water barrier - forms between stratum granulosum and stratum spinosum
•consists of: –lipids secreted by keratinocytes –tight junctions between keratinocytes –thick layer of insoluble protein on the inner surfaces of the keratinocyte plasma membranes •critical to retaining water in the body and preventing dehydration •cells above the water barrier quickly die –barrier cuts them off from nutrients below –dead cells exfoliate (dander) –dandruff – clumps of dander stuck together by sebum (oil) |
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Dermis
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•dermis – connective tissue layer beneath the epidermis
•ranges from 0.2 mm (eyelids) – 4 mm (palms & soles) •composed mainly of collagen with elastic fibers, reticular fibers, and fibroblasts •well supplied with blood vessels, sweat glands, sebaceous glands, and nerve endings •hair follicles and nail roots are embedded in dermis •smooth muscle (piloerector muscles) associated with hair follicles –contract in response to stimuli, such as cold, fear, and touch – goose bumps |
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Dermis
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•dermal papillae – upward fingerlike extensions of the dermis
–friction ridges on fingertips that leave fingerprints •papillary layer – superficial zone of dermis –thin zone of areolar tissue in and near the dermal papilla –allows for mobility of leukocytes and other defense cells should epidermis become broken –rich in small blood vessels •reticular layer – deeper and much thicker layer of dermis –consists of dense, irregular connective tissue –stretch marks (striae) – tears in the collagen fibers caused by stretching of the skin due to pregnancy or obesity |
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Structure of the Dermis
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Hypodermis
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•subcutaneous tissue
•more areolar and adipose than dermis •pads body •binds skin to underlying tissues •drugs introduced by injection –highly vascular & absorbs them quickly •subcutaneous fat –energy reservoir –thermal insulation –8% thicker in women |
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Hypodermis dermis
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Skin Color
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•melanin – most significant factor in skin color
–produced by melanocytes –accumulate in the keratinocytes of stratum basale and stratum spinosum –eumelanin – brownish black –pheomelanin - a reddish yellow sulfur-containing pigment •people of different skin colors have the same number of melanocytes –dark skinned people •produce greater quantities of melanin •melanin granules in keratinocytes more spread out than tightly clumped •melanin breaks down more slowly •melanized cells seen throughout the epidermis –light skinned people •melanin clumped near keratinocyte nucleus •melanin breaks down more rapidly •little seen beyond stratum basale •amount of melanin also varies with exposure to |
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Other factors in skin color
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•hemoglobin - red pigment of red blood cells
–adds reddish to pinkish hue to skin •carotene - yellow pigment acquired from egg yolks and yellow/orange vegetables –concentrates in stratum corneum and subcutaneous fat |
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Abnormal Skin Colors
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•cyanosis - blueness of the skin from deficiency of oxygen in the circulating blood
–airway obstruction (drowning or choking) –lung diseases (emphysema or respiratory arrest) –cold weather or cardiac arrest •erythema – abnormal redness of the skin due to dilated cutaneous vessels –exercise, hot weather, sunburn, anger, or embarrassment •pallor – pale or ashen color when there is so little blood flow through the skin that the white color of dermal collagen shows through –emotional stress, low blood pressure, circulatory shock, cold, anemia •albinism – genetic lack of melanin that results in white hair, pale skin, and pink eyes –have inherited recessive, nonfunctional tyrosinase allele •jaundice - yellowing of skin and sclera due to excess of bilirubin in blood –cancer, hepatitis, cirrhosis, other compromised liver function •hematoma – (bruise) mass of clotted blood showing through skin |
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Structure of Hair Follicle
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•follicle – diagonal tube that dips deeply into dermis and may extend into hypodermis
–epithelial root sheath • extension of the epidermis •lies immediately adjacent to hair root •toward deep end widens into bulge - a source of stem cells for follicular growth –connective tissue root sheath •derived from dermis •surrounds epithelial root sheath •denser than adjacent connective tissue •hair receptors –nerve fibers that entwine each follicle –respond to hair movement •piloerector muscle (arrector pili) –bundles of smooth muscle cells –extends from dermal collagen to connective tissue root sheath -goose bumps |
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Structure of Hair Follicle
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Dermis
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Within the dermis
•dermal papillae – upward fingerlike extensions of the dermis –friction ridges on fingertips that leave fingerprints |
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Dermis
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Within dermis
•papillary layer – superficial zone of dermis –thin zone of areolar tissue in and near the dermal papilla –allows for mobility of leukocytes and other defense cells should epidermis become broken –rich in small blood vessels |
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Dermis
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Within the dermis
•reticular layer – deeper and much thicker layer of dermis –consists of dense, irregular connective tissue –stretch marks (striae) – tears in the collagen fibers caused by stretching of the skin due to pregnancy or obesity |
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melanin
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– most significant factor in skin color
–produced by melanocytes –accumulate in the keratinocytes of stratum basale and stratum spinosum –eumelanin – brownish black –pheomelanin - a reddish yellow sulfur-containing pigment |
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people of different skin colors have the same number of melanocytes
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–dark skinned people
•produce greater quantities of melanin •melanin granules in keratinocytes more spread out than tightly clumped •melanin breaks down more slowly •melanized cells seen throughout the epidermis –light skinned people •melanin clumped near keratinocyte nucleus •melanin breaks down more rapidly •little seen beyond stratum basale |
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cyanosis
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- blueness of the skin from deficiency of oxygen in the circulating blood
–airway obstruction (drowning or choking) –lung diseases (emphysema or respiratory arrest) –cold weather or cardiac arrest |
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erythema
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– abnormal redness of the skin due to dilated cutaneous vessels
–exercise, hot weather, sunburn, anger, or embarrassment |
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pallor
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– pale or ashen color when there is so little blood flow through the skin that the white color of dermal collagen shows through
–emotional stress, low blood pressure, circulatory shock, cold, anemia |
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albinism
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– genetic lack of melanin that results in white hair, pale skin, and pink eyes
–have inherited recessive, nonfunctional tyrosinase allele |
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jaundice
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- yellowing of skin and sclera due to excess of bilirubin in blood
–cancer, hepatitis, cirrhosis, other compromised liver function |
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hematoma
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– (bruise) mass of clotted blood showing through skin
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epithelial root sheath
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• extension of the epidermis
•lies immediately adjacent to hair root •toward deep end widens into bulge - a source of stem cells for follicular growth |
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connective tissue root sheath
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•derived from dermis
•surrounds epithelial root sheath •denser than adjacent connective tissue |
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hair receptors
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–nerve fibers that entwine each follicle
–respond to hair movement |
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piloerector muscle (arrector pili)
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–bundles of smooth muscle cells
–extends from dermal collagen to connective tissue root sheath –goose bumps |
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Structure of hair
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Hair Growth and Loss
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•hair cycle – consists of three developmental stages
–anagen - growth stage - 90% of scalp follicles at any given time •stem cells multiply and travel downward •pushing dermal papilla deeper into skin forming epidermal root sheath •root sheath cells directly above dermal papilla form the hair matrix •sheath cells transform into hair cells, synthesize keratin, and die as they are pushed upward •new hair grows up the follicle, often alongside of an old club hair from the previous cycle –catagen - degenerative stage - mitosis in the hair matrix ceases and sheath cells below the bulge die •the follicle shrinks and the dermal papilla is drawn up toward the bulge •base of hair keratinizes into a hard club, and hair is now known as club hair –loses its anchorage –easily pulled out by brushing –telogen - resting stage - when papilla reaches the bulge |
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Anagen stage of hair cycle
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growth stage - 90% of scalp follicles at any given time
•stem cells multiply and travel downward •pushing dermal papilla deeper into skin forming epidermal root sheath •root sheath cells directly above dermal papilla form the hair matrix •sheath cells transform into hair cells, synthesize keratin, and die as they are pushed upward •new hair grows up the follicle, often alongside of an old club hair from the previous cycle |
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Cycle of hair
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catagen stage of hair cycle
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- degenerative stage - mitosis in the hair matrix ceases and sheath cells below the bulge die
•the follicle shrinks and the dermal papilla is drawn up toward the bulge •base of hair keratinizes into a hard club, and hair is now known as club hair –loses its anchorage –easily pulled out by brushing |
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telogen stage of hair cycle
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resting stage - when papilla reaches the bulge
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hirsutism
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– excessive or undesirable hairiness in areas that are not usually hairy
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pattern baldness
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the condition in which hair loss from specific regions of the scalp rather than thinning uniformly
–combination of genetic and hormonal influence –baldness allele is dominant in males and expressed only in high testosterone levels –testosterone causes terminal hair in scalp to be replaced by vellus hair |
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alopecia
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thinning of the hair or baldness
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Hair growth & loss
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•club hair may fall out during catagen or telogen
–or pushed out by new hair in the next anagen phase •we lose about 50 – 100 scalp hairs daily •in young adult the scalp follicles spend: –6 – 8 years in anagen, 2 – 3 weeks in catagen, 1 - 2 months in telogen •hair growth - scalp hairs grow at a rate of 1 mm per 3 days (10 -18 cm/yr) |
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Functions of Hair
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•most hair on trunk and limbs is vestigial
–little present function –warmth in ancestors •hair receptors alert us of parasites crawling on skin •scalp helps retain heat •scalp protects against sunburn •gender identification •pubic and axillary hair signify sexual maturity and aids in transmission of sexual scents •guard hairs (vibrissae) - guard nostrils and ear canals •eyelashes and eyebrows •nonverbal communication |
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Fingernail Structure
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Nails
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•fingernails and toenails - clear, hard derivatives of the stratum corneum
•composed of very thin, dead cells packed with hard keratin •flat nails allow for more fleshy and sensitive fingertips –tools for digging, grooming, picking apart food, and other manipulations •nail plate – hard part of the nail –free edge – overhangs the finger tip –nail body – visible attached part of nail –nail root – extends proximally under overlying skin •nail fold – surrounding skin rising a bit above the nail •nail groove – separates nail fold from nail plate •nail bed – skin underlying the nail plate •hyponychium – epidermis of the nail bed •nail matrix – growth zone of thicken stratum basale at the proximal end of nail –mitosis here accounts for nail growth –1 mm per week in fingernails, slightly slower on toenails •lunule – an opaque white crescent at proximal end of nail •eponychium (cuticle) – narrow zone of dead skin commonly |
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5 types of skin glands
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- merocrine sweat glands
- apocrine sweat glands - sebaceous glands - ceruminous glands - mammary glands |
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- apocrine sweat glands
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Sebaceous gland
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merocrine sweat glands
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Apocrine Glands
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•More oily than eccrine glands
•Restricted locations –Mostly armpits, groin •Related to other glands –Ceruminous glands •Ear canal, produce wax – Cillary glands •Eyelids –Mammary glands |
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Apocrine Glands
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Sebaceous Glands
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•Associated with hair follicle
•Produce sebum –Holocrine secretion –Oily secretion –Keeps hair and skin from drying |
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Sebaceous Glands
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Skin Cancer
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induced by the ultraviolet rays of the sun
–most often on the head and neck –most common in fair-skinned people and the elderly –one of the most common cancers –one of the easiest to treat –has one of the highest survival rates if detected and treated early –three types of skin cancer named for the epidermal cells in which they originate –basal cell carcinoma, squamous cell carcinoma, and malignant melanoma |
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Basal Cell Carcinoma
Skin cancer |
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Squamous Cell Carcinoma
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Squamous Cell Carcinoma
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- arise from keratinocytes from stratum spinosum
- lesions usually appear on scalp, ears, lower lip, or back of the hand - have raised, reddened, scaly appearance later forming a concave ulcer - chance of recovery good with early detection and surgical removal - tends to metastasize to lymph nodes and may become lethal |
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Basal Cell Carcinoma
Skin cancer |
- most common type
- least dangerous because it seldom metastasizes - forms from cells in stratum basale - lesion is small shiny bump with central depression and beaded edges |
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Malignant Melanoma
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- skin cancer that arises from melanocytes
- often in a preexisting mole - less than 5% of skin cancers, but most deadly form - treated surgically if caught early - metastasizes rapidly - unresponsive to chemotherapy - usually fatal - person with metastatic melanoma lives only 6 months from diagnosis - 5% - 14% survive 5 years - greatest risk factor – familial history of malignant melanoma - high incidence in men, redheads, people who experience severe sunburn in childhood |
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Sweat
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- begins as a protein-free filtrate of blood plasma produced by deep secretory portion of gland
–potassium ions, urea, lactic acid, ammonia, and some sodium chloride remain in the sweat, most sodium chloride reabsorbed by duct –some drugs are also excreted in sweat –on average, 99% water, with pH range of 4 to 6 •acid mantle – inhibits bacterial growth –insensible perspiration – 500 ml per day •does not produce visible wetness of skin –diaphoresis – sweating with wetness of the skin •exercise – may lose one liter of sweat per hour |
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UVA, UVB and Sunscreens
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•UVA and UVB are improperly called “tanning rays” and “burning rays”
•both thought to initiate skin cancer •sunscreens protect you from sunburn but unsure if provide protection against cancer –chemical in sunscreen damage DNA and generate harmful free radicals |
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Burns
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•burns – leading cause of accidental death
–fires, kitchen spills, sunlight, ionizing radiation, strong acids or bases, or electrical shock –deaths result primarily from fluid loss, infection and toxic effects of eschar – burned, dead tissue debridement – removal of eschar •classified according to the depth of tissue involvement –first-degree burns – partial thickness burn - involve only the epidermis •marked by redness, slight edema, and pain •heal in a few days •most sunburns are first degree burns –second-degree burns – partial thickness burn - involve the epidermis and part of the dermis •leaves part of the dermis intact •red, tan, or white •two weeks to several months to heal and may leave scars •blistered and very painful –third-degree burn – full thickness burn – the epidermis and all of the dermis, and often some deeper tissues (muscles or bones) are destroyed |
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Degrees of burns
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Skin Grafts and Artificial Skin
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•third-degree burns require skin grafts
•graft options –autograft - tissue taken from another location on the same person’s body •split-skin graft – taking epidermis and part of the dermis from an undamaged area such as the thigh or buttocks and grafting it into the burned area –isograft - skin from identical twin •temporary grafts (immune system rejection) –homograft (allograft) -- from unrelated person –heterograft (xenograft) -- from another species –amnion from afterbirth –artificial skin from silicone and collagen |
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•temporary grafts (immune system rejection)
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–homograft (allograft) -- from unrelated person
–heterograft (xenograft) -- from another species –amnion from afterbirth –artificial skin from silicone and collagen |
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–homograft (allograft)
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Skin graft from unrelated person
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Heterograft (xenograft)
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skin graft from another species
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Amnion
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Skin graft from from afterbirth
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artificial skin
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Skin graft from silicone and collagen
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•graft options
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–autograft - tissue taken from another location on the same person’s body
•split-skin graft – taking epidermis and part of the dermis from an undamaged area such as the thigh or buttocks and grafting it into the burned area –isograft - skin from identical twin |
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Eccrine Sweat Glands
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Types of tissues (4)
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–epithelial tissue
–connective tissue –nervous tissue –muscular tissue |
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Basement membrane
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A thin, delicate layer of connective tissue underlying the epithelium of many organs. Also called basement lamina.
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Basement membrane
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Basement membrane
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basal lamina
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is a layer of extracellular matrix secreted by the epithelial cells, on which the epithelium sits. It is often confused with the basement membrane, and sometimes used inconsistently in the literature, see below.
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basal lamina
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lamina propria
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is a constituent of the moist linings known as mucous membranes or mucosa, which line various tubes in the body (such as the respiratory tract, the gastrointestinal tract, and the urogenital tract).
The lamina propria (more correctly lamina propria mucosæ) is a thin layer of loose connective tissue, or dense irregular connective tissue, which lies beneath the epithelium and together with the epithelium constitutes the mucosa. Thus the term mucosa or mucous membrane always refers to the combination of the epithelium plus the lamina propria.[1] The lamina propria contains capillaries and a central lacteal (lymph vessel) in the small intestine, as well as lymphoid tissue. Lamina propria also contains glands with the ducts opening on to the mucosal epithelium, that secrete mucus and serous secretions. The lamina propria is also rich in immune cells known as lymphocytes. |
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lamina propria
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lamina propria
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extracellular matrix
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Complex network of polysaccharides (such as glycosaminoglycans or cellulose) and proteins (such as collagen) secreted by cells. Serves as a structural element in tissues and also influences their development and physiology.
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extracellular matrix
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extracellular matrix
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not only provides structural support to cells and tissues, but also plays important roles in regulating the behavior of cells in multicellular organisms
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eccrine glands
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are sweat glands that are not connected to hair follicles. They function throughout life by responding to elevated body temperature due to environmental heat or physical exercise. These glands are common on the forehead, neck, and back, where they produce profuse sweating on hot days and when a person is physically active. They also are responsible for the moisture that may appear on the palms and soles when a person is emotionally stressed.
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eccrine glands
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