Veterinary Histology: The Cell-Membranes And Organelles

Front 1

Which organelles are visible with the light microscope?

Back 1

-plasma membrane
-nucleus
-golgi
-nucleolus
-mitochondria
-centriole

Front 2

Cell membrane composition

Back 2

-composed of phospholipids, cholesterol and protein molecules
-bi-layered arrangement
-hydrophobic portion is at the center
-hydrophilic is on the surfaces

Front 3

Glycocalyx

Back 3

-consists of the glycoproteins, glycolipids and secreted proteoglycans that make up the carbohydrate rich zone of the cell surface
-carries a "code"

Front 4

Membrane protein functions

Back 4

-ion pumps
-channels
-membrane receptors (recognizes and binds specific ligands such as hormones, neurotransmitters, etc)
-enzymes
-structural proteins

Front 5

Endocytosis (3 types)

Back 5

-Pinocytosis: non-specific ingestion of fluid and small protein molecules via small vesicles

-Receptor-mediated endocytosis: allows entry of specific molecules (cargo receptors)

-Phagocytosis: ingestion of large particles such as bacteria, cell debris, etc performed by specialized cells called macrophages or histiocytes

Front 6

Endosomes

Back 6

-membrane bound structures associated with any of the endocytotic pathways

Front 7

Early endosomes

Back 7

-near cell membrane
-important for sorting and recycling of proteins internalized by various endocytotic pathways

Front 8

Late endosomes

Back 8

-formed from early endosomes
-travel deeper into the cytoplasm
-eventually develop into lysosomes
-regulate amount of transporter proteins to and from the plasma membrane

Front 9

Lysosomes

Back 9

-membrane bound organelles
-rich in hydrolytic enzymes synthesized by the rER, modified by the Golgi and packed into the lysosomes

Front 10

Lysosomal enzymes

Back 10

-acid phosphatase
-glucuronidase
-ribonuclease
-lipase
-collagenase

Front 11

Phagolysosomes

Back 11

-primary lysosomes fuse with phagosomes to form secondary lysosomes aka phagolysosomes

Front 12

Autophagy

Back 12

-removal, digestion and reprocessing of damaged and worn out organelles
-lysosomes play a big role in this process

Front 13

Heterophagy

Back 13

-process by which lysosomes ingest and breakdown material from teh external environment
-performed by macrophages

Front 14

Lysosomal Storage Diseases

Back 14

-can result in the accumulation of substrates within the cell and can make cells swell

Front 15

Rough Endoplasmic Reticulum

Back 15

-studded with ribosomes so it functions in protein synthesis
-cells with a lot of rER have basophilic cytoplasm
-continuous with the outer layer of the nuclear envelope

Front 16

Smooth Endoplasmic Reticulum

Back 16

-no ribosomes
-important in metabolism of exogenous chemicals that may be toxins
-these detox reactions are performed by the p-450 mixed function oxidase system
-common in the liver and in cells that synthesize and secrete steroid hormone

Front 17

Golgi

Back 17

-functions in post-translational modification and sorting and packing of proteins synthesized by the cell
-found in cells that make a lot of membrane associated protein
-appear as a clear zone in H&E

Front 18

Mitochondria

Back 18

-have circular DNA
-have their own ribosomes
-abundant in cells with high energy requirements

Front 19

How do mitochondria make ATP?

Back 19

-beta oxidation of fatty acids
-oxidative phosphorylation

Front 20

Mitochondrial role in apoptosis

Back 20

-mediated by release of cytochrome c through the mitochondrial membrane into the cytoplasm
-regulated by Bcl-2 proteins which initiate a cascade of proteolytic enzymatic reactions resulting in DEATH

Front 21

Peroxisomes

Back 21

-contain catalase and other oxidative enzymes
-beta oxidation of fatty acids also occurs
-prominent in hepatocytes and renal tubular cells

Front 22

Cell Membrane Injury

Back 22

-occurs through: chemicals, infectious agents, physical trauma, nutritional imbalances and immune mediated reactions
-results in: loss of ability to maintain a selectively permeable barrier

Front 23

Carbon tetrachloride Toxicity

Back 23

-liver cell toxin that injures the cell membrane when it is converted to the trichloromethyl radical CCl3 by the sER

Front 24

Perforation of cell membrane

Back 24

killing strategy used by:
-bacterial toxins (E.Coli, Staph aureus)
-perforins (natural killer cells)"
-complement
-defensins (antibacterial molecules)

Front 25

Actin filaments

Back 25

-6-8nm in diameter
-found in bundles close to the cell membrane
-functions:
-internal mechanical support
-anchor membrane junctions
-"railroad track" for internal transport of vesicles and organelles
-component of cilia and microvilli
-scaffold for myosin in muscle cells

Front 26

Spectrin

Back 26

-cytoskeletal protein that lines the inner surface of the plasma membrane
-arranged in a pentagonal or hexagonal configuration
-maintains cytoskeletal structure and membrane shape

Front 27

Intermediate Filaments

Back 27

-8-10nm in diameter
-supporting function in the cytoplasm
-subdivided into four classes
1. keratins or cytokeratins-epithelial
2. vimentin and desmin-mesenchymal
3. neurofilaments- nerve cells
4. lamins- nuclear envelope and nuceloplasm

Front 28

Which cytoskeleton component helps diagnose cancer and how?

Back 28

-intermediate filaments
-antibodies directed toward them are used to classify poorly differentiated maligmant tumors based on embryonic germ layer origin

Front 29

Disease involving actin filaments

Back 29

-toxins of poisonous mushrooms (Amanita phalloides) binds to actin and prevents their depolarization
-results in rapid cell death by necrosis

Front 30

Microtubules

Back 30

-20-25nm in diameter
-ridged, non-branching, hollow tubes
-forms a system of connections in the cytoplasm on which vesicles can move
-unstable structures that are constantly assembling/diassembling
-essential to the movement of chromosomes during mitosis and meiosis
-represent the core of cilia and flagella

Front 31

Centrioles

Back 31

-paired, short, rod-like cylinders that are formed from microtubules
-surrounded by golgi
-associated with a zone of amorphous pericentriolar material known as the microtubule organizing center

Front 32

Microtubule Organizing Center (MTOC)

Back 32

-zone of amorphous pericentriolar material
-microtubules are formed here and directed to their locations in the cell

Front 33

Intracellular Inclusions (General)

Back 33

-found in cytoplasm and nucleus of cells
-products of metabolic activity and have special staining properties

Front 34

Lipofuscin

Back 34

-intracellular inclusion
-brown/yellow pigment seen in neurons and muscle cells
-result of oxidative degradation of mitochondria and lysosomal digestion

Front 35

Hemosiderin

Back 35

-intracellular inclusion
-dark brown/brown/yellow iron containing pigment that cannot be distinguished from lipofuscin in H&E

Front 36

Glycogen

Back 36

-liver cells and striated muscle fibers have a lot
-periodic acid-schiff stain is used to show this material (magenta)

Front 37

Lipid

Back 37

-cells with lipid appear to have clear space
-oil red-O stains lipid bright red

Front 38

Pathologic Intracellular Inclusions

Back 38

-viral infection
-RNA virus->cytoplasm
-DNA virus->nucleus
-toxicity
-alcohol->mallory body
-lead-> intranuclear inclusion

Front 39

Karyogenic hypothesis

Back 39

-nucleus resulted from a process of segregating DNA to a region of the cell where another membrane surrounded it
-not likely to be correct

Front 40

Endokaryotic hypothesis

Back 40

-one prokaryote was phagocytosed by another and survived and became incorporated

Front 41

What advantages do eukaryotic cell have over prokaryotic cells?

Back 41

1. development of a larger genome
2. spatial separation of transcription and translation

Front 42

Chromatin

Back 42

-nucleoprotein complex which is composed of DNA in addition to structural proteins called histones
-

Front 43

Heterochromatin

Back 43

-densely stained, clumped region
-low level of transcription

Front 44

Euchromatin

Back 44

-uncoiled/stretched out regions of DNA
-actively being read and transcribed

Front 45

Nuclear pores

Back 45

-holes in the nuclear membrane that allow communication between nucleoplasm and cytoplasm
-allows passage of RN?a dn ribonucleoproteins between nucleus and cytoplasm

Front 46

Nuclear lamina

Back 46

-thin, electron dense protein layer
-has a supporting or nucleoskeletal function
-composed of proteins called lamins (similar to intermediate filaments)

Front 47

Lamin Disease

Back 47

-impairment of nuclear lamine is associated with several human genetic disorders including progeria

Front 48

Nucleolus

Back 48

-non-membrane bound region of the nucleus
-contains transcriptionally active RNA genes
-site of rRNA synthesis
-prominent in cells secreting protein

Front 49

Telomeres

Back 49

-region of highly repetitive DNA at the end of a chromosome
-helps prevent loss of genetic information due to the fact that DNA polymerase cannot replicate all of the way to the end of a chromosome
-cancer cells have telomerase that is constantly turned on

Front 50

Cell Turnover

Back 50

-measured by counting the number of mitotic figures in a single high powered light microscopic field

-static: no longer capable of division (neurons, cardiac muscle)
-stable: undergoing periodic division (liver, CT cells)
-continuously dividing: always dividing (epithelial cells, bone marrow)

Front 51

Interphase

Back 51

-period of continuous growth
-Subdivided into:
G1
S
G2

Front 52

Mitosis/M phase

Back 52

-halving of genome occurs here
-subdivided into:
Prophase
Metaphase
Anaphase
Telophase

Front 53

Mitotic catastrophe

Back 53

-results in aberrant chromosome segregation with the generation of aneuploid cells

Front 54

Hyperplastic/Neoplastic Disease

Back 54

-excessive cell production

Front 55

Hypoplasic/atrophic disease

Back 55

-decreased cell division or excessive cell loss

Front 56

Necrosis

Back 56

-initated by external factors such as hypothermia, heat, low pH, radiation, microbial pathogens
-die by swelling and membrane rupture
-results in a secondary inflammatory response

Front 57

Apoptosis

Back 57

-internal programming to eliminate cells no longer needed or cells with irreparable damage
-is usually a normal process (unlike necrosis)
-can be induced by external factors:
-tumor necrosis factor produced by macrophages in response to bacterial infection
-TGF-beta
-free radicals
-UV light
-ionizing radiation
-also activated when accidents in the cell cycle result in malfunction of DNA damage checkpoints