Bio 231 @ Oit - Lecture 3

Front 1

Bone is composed of?

Back 1

- Hard connective tissue composed of osteocytes and a mineralized matrix
- Matrix provides strength to bone.
-- Organic: collagen fibers
-- Inorganic: hydroxyapetite (calcium and phosphate).
- Osteocytes located in lacunae
-- Cancellous or spongy bone
-- Compact bone

Front 2

How does Cancellous bone differ from other types?

Back 2

- Cancellous or spongy bone has numerous empty spaces between the supportive trabeculae
- Has the appearance of a natural sponge
- Spongy bone located within the body of the bone, pores contain red bone marrow

Front 3

How does Compact bone differ from other types?

Back 3

- compatct bone is arranged in concentric layers around a central canal which contains a blood vessel.
- The osteoblast deposits the mineral matrix and collagen fibers. Once this cell is surrounded by the matrix, it is called an osteocyte
- All bony tissue is enclosed within a layer of connective tissue (periosteum)

Front 4

What is blood composed of?

Back 4

- Plasma
-- Liquid matrix which lacks protein fibers
- Formed elements: red cells, white cells, and platelets
- Hemopoietic tissue
-- Red bone marrow forms the blood cells

Front 5

What are the functions of the integument?

Back 5

Functions:
- Protection - nonspecific immunity and prevents desiccation
- Sensory - highly sensitvie to the external environment
- Thermoregulation - accomplished by vasodilation, vasoconstriction, and insulation
- Vitamin D synthesis - precursor to the hormone calcitrol (calcium absorption)

Front 6

What are the three layers of the integument? (histology)

Back 6

- Epidermis - keratinized stratified squamous epithelium
- Dermis
-- Papillary layer - aerolar c.t. (20%)
-- Reticular layer - dense irregular c.t. (80%)
-Hypodermis - superficial fascia, adipose tissue, areolar c.t. and blood vessels. ***Not part of the integument.

Front 7

Describe the characteristics of the epidermis

Back 7

- composed of keratinized stratified squamous epithelium
- avascular, typical for all epithelial tissue
- arranged in 4 or 5 distinct histological layers (strata)
- Cell types include:
-- Keratinocytes
-- Melanocytes
-- Merkel cells
-- Langerhans cells
- Between 35-45 days entire epidermal layer will regenerate

Front 8

What cell types are found in the integument?

Back 8

- Keratinocytes represent 90% of all cells, secrete the protein keratin
- Melanocytes secrete melanin, provides protection from ultra-violet radiation.
- Merkel cells serve as sensory receptors to touch
- Langerhans cells (epidermal dendritic cells) originate from bone marrow and migrate to the epidermis. Part of the immune system, engulf foreign antigens)

Front 9

Layers of the epidermis: Stratum basale - Describe

Back 9

Layers of the epidermis: stratum basale:
- Deepest epithelial layer or strata
- A single layer of cells which undergo continuous replication (mitosis).
- Merkel cells and melanocytes also located with this layer
- The protein melanin shields the basal cell nuclei from U.V. radiation, which damage the DNA molecule and disrupt normal cellular replication.
- Merkel cells associated with underlying sensory neurons (touch).

Front 10

Layers of the epidermis: Stratum spinosum - Describe

Back 10

- Characteristic spiny appearance as a result of cell-cell contact (desmosomes).
- Several cell layers in thickness.
- Cells begin to transport the secreted melanin protein into intracellular compartment.
- Langerhans cells also located within this layer.

Front 11

Layers of the epidermis: Stratum granulosum - Describe

Back 11

- Thin layer (3-5) of flattened keratinocytes
- Cell membranes thicken, cells flatten, organells and nucleus disintegrate
- Gradually cells begin to die as they become more superficial
- The process of keratinization begins, cells contain granules of keratin
- A glycolipid is secreted into the extracellular space and functions as a waterproofing agent (prevents desiccation).

Front 12

Layers of the epidermis: Stratum lucideum - Describe

Back 12

- Occurs only on the soles of the feet and the palms of the hands (thick skin).
- Appears as a thin clear zone under the microscope (3-5 cell layers).
- In other anatomical regions this layer is absent and is called thin skin.

Front 13

Layers of the epidermis: Stratum corneum - Describe

Back 13

- The most superficial layer, represented by 25-30 cellular layers of dead flattened keratinocytes
- Cells contain an abundance of keratin
- This layer protects the underlying layers of the integument from abrasiona nd penetration of foreign bodies.
- cells of this layer are continually shedding

Front 14

Describe the structure of the dermis

Back 14

- Represented by connective tissue, collagen and elastic fibers, fibroblasts, macrophages, blood vessels, sensory receptors, glands, and hair follicles
- Based on histology is separated into two layers:
-- Superficial papillary layer
-- Deep reticular layer
- Sensory funcitons: pain, itch, tickle, temperature, touch, pressure, two-point discrimination

Front 15

Describe the papillary layer of the dermis

Back 15

- This layer is composed of aerolar connective tissue
- Contains peg-like projections called dermal papillae which contribute in the formatino of epidermal ridges
- The epidermal ridges increase surface area/friction and improves the grip of the hands & feet
- Oil and sweat residues associated with friction ridges generate fingerprints

Front 16

Describe the composition of the reticular layer

Back 16

- Composed of dense irregular connective tissue
- Contains an abundance of the collagen fibers which give the skin its strength
- Separations or less dense areas between bundles of collagen fibers are called cleavage or tension lines
- Elastic fibers also located in this layer, allows for stretch and recoil of the skin

Front 17

Describe sweat glands

Back 17

- Also known as sudoriferous glands, are distributed over the entire skin except the nipple and external genitalia
- Sweat is 99% water and sodium chloride and traces of urea, ammonia, and uric acid
- Two types: eccrine and apocrine

Front 18

What discriminates Eccrine glands?

Back 18

- Eccrine also known as merocrine are more numerous on the palms, soles of the feet, and forehead.
- The glandular tissue is located within the dermis, the duct of an eccrine sweat gland opens directly to the skin surface.
- Essential for thermoregulation, sweating is regulated by the sympathetic nervous system

Front 19

What discriminates Apocrine glands?

Back 19

- Apocrine sweat glands confined to the axillary and genital regions
- Ducts of apocrine glands open onto hair follicles, similar secretions as eccrine glands but have addition of lipids and proteins
- Becomes functional at puberty under the influence of sex hormones, no role in thermoregulation

Front 20

What discriminates Sebaceous glands

Back 20

- Located over entire body except thick skin of palms and soles.
- Most of all sebaceous glands develop from the hair follicle, the oil or sebum is secreted directly onto the hair follicle.
- Sebum will soften and lubricate the skin, keeping it from cracking
- Secretions of sebum is stimulated by hormonal activity

Front 21

Describe the composition of the hypodermis

Back 21

- Composed of aerolar connective tissue and adipose tissue.
- Also known as superficial fascia
- Attaches the dermis to underlying muscle and bone
- Is the site of deposition for adipose (fat)
- Functions as an insulator (retains body heat)

Front 22

Describe the composition of hair

Back 22

- consists of dead keratinized cells originating from the hair bulb (epidermal derivative)
- Found everywhere on the human body except palms, soles, lips, nipples, and parts of external genitalia.
- Hair represented by three concentric layeros of dead cells, the medulla, the cortex (color) and cuticle
- Hair shaft protrudes above skin surface
- Hair root located below surface; base of root is the harb bulb (germinal layer)
- Sensory nerve endings associated with hair bulb, sensitive to touch

Front 23

Describe the composition of nails

Back 23

- Modified keratinized epidermal cells on the distal ends of digits
- Homologous with claws and hooves
- Represented by: free edge, body, and root (embedded in skin)
- Nail root (matrix) responsible for growth