7 - Histology Flashcards by mikayla kozarchuk

Define histology

Study of tissues

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What are cell junctions? Where are they found?

 points of contact between adjacent cells - seen in epithelial tissue, some nervous and muscle cells
 formed by cell membrane proteins

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What are the types of cell junctions?

Tight Junctions
Anchor Junctions
Gap Junctions

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Describe tight junctions

 are a partial fusion of specific proteins on the lateral surface of the cell membrane
 form ring-like tight seal
 prevents material from passing between cells e.g. bacteria, proteins, sometimes fluid or ions (depending on the tissue)

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Describe anchor junctions. What is an example?

e.g. desmosomes

 proteins that fasten cells to each other and/or extracellular material (“rivets” cells together)

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Describe gap junctions

 open channels (formed by proteins) through the adjacent cell membranes interconnecting the cytosols of the cells
 allows ions/small molecules to pass from one cell to another
 tissues can then work as a unit:
o important in cardiac and smooth muscle (allows synchronization of contractions)
o also found in epithelial tissue

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What is the function of epithelial tissue?

 covers body surface (skin)

 lines body/organ cavities

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What is a lumen?

o organ cavity = lumen (lumen is a cavity, not a layer)

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What are the characteristics of epithelia?

o has one free surface (next to blood, food, or air)
o little extracellular space between cells
o avascular – no blood vessels

o Basement membrane (division between epithelia and ct)
 extracellular layer
 attaches epithelium to underlying CT layer (formed by both tissues – “velcro”)

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What is an epithelial layer called if it has only one layer of cells? Multiple Layers?
Flattened cells?
Square or round cells?
Tall Cells?

Simple, Stratified
Squamous
Cuboidal
Columnar

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Why would epithelial cells be simple? (mono-layered)

 allow exchange of molecules (gasses, nutrients, etc.) – absorption/secretion

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Where might you find a simple squamous layer?

Lungs

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Where might you find a simple cuboidal layer?

Kidneys

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Where might you find a simple columnar layer?

Stomach, Small intestine

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Why would epithelial cells be stratified?

To protect from abrasion

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Where might you find a stratified squamous layer?

Skin!

Where might you find a stratified cuboidal layer? Columnar?

rare.

What is a pseudostratified epithelial layer?

 appears stratified (nuclei at different levels), but all cells sit on basement membrane (= simple!)

Where might you find a pseudostratified layer?

Respiratory tract (ciliated)

What is a transitional epithelial layer?

cell shape (& layering) varies with stretching
 only in inner lining of urinary system
 cuboidal to squamous when stretched

What is a glandular epithelia?

if the epithelial cells form a gland, the cell layer(s)/cell shape classification is no longer used, and we call it glandular.
Used for secretion.

What are the subtypes of glandular epithelia?

Exocrine

Endocrine

Describe Exocrine glands

 secrete products onto body surface or into a body cavity
 can be:
i. unicellular
 e.g. goblet cells
ii. multicellular
 consists of secretory and duct cells (ducts connect secretions to surface or cavity)
 e.g. glands: sudoriferous (sweat), sebaceous (oil), mammary, digestive

Describe endocrine glands

 no ducts (ductless)
 secretions (hormones) into the blood
 e.g. thyroid gland secretes thyroid hormone

What are the three functions of epithelia?

``` 1) Protection  often stratified squamous  e.g. epidermis of skin 2) Secretion  glandular epithelium  e.g. thyroid, sweat glands 3) Control of permeability  typically simple epithelia  exchange of material  e.g. kidney, intestine, capillaries ```

Define connective tissue

 mainly supports and connects tissues  cells far apart, separated by extracellular matrix o extracellular material gives CT subtypes their identifying characteristics  variable vascularity

What are the three CT cell types, and what are their functions? (think suffixes)

``` o cell names ending in:  -BLAST – create matrix  e.g. osteoblast, chondroblast, fibroblast  -CYTE – maintain matrix  e.g. osteocyte, chondrocyte, fibrocyte  -CLAST – break down matrix  osteoclast ```

What is the extracellular matrix made of?

1) Fibres (proteins)  collagen fibres (for strength)  elastic fibres (containing elastin - allow stretch and recoil)  reticular fibres (form networks – e.g. CT part of basement membrane) 2) Ground Substance  unstructured material surrounding the extracellular fibres and cells  composed of: a) Interstitial Fluid (ISF) = part of blood plasma that leaks out of capillaries and surrounds cells b) proteoglycans = protein + carbohydrate molecule (e.g. hyaluronic acid, chondroitin sulphate) 3) Water

How do we classify CT cells?

By their matrix

What are the 4 classifications of CT cells?

CT Proper Cartilage Bone Blood

What defines a CT cell as being CT proper

 cells = fibroblasts/fibrocytes except (as well as) adipose tissue (adipocytes)

What are the 2 types of CT Proper?

Loose CT | Dense CT

What are the 2 types of Loose CT Proper?

``` i. areolar CT  loosely arranged collagen and elastin fibres surrounded by ground substance (hyaluronic acid)  highly vascular  e.g. lamina propria ii. adipose CT  very little matrix  cells large (adipocytes), store triglycerides - tissue looks like “chicken-wire”  highly vascular ```

Define dense CT Proper and it's types

```  many fibres (a.k.a. fibrous CT)  little ground substance  poorly vascular  types: i. dense regular CT  collagen fibres running in the same direction  e.g. tendons, ligaments ii. dense irregular CT  collagen fibres arranged irregularly  e.g. dermis of skin ```

Describe cartilage

 cells = chondrocytes (cells located in lacunae = cavities in the matrix) & chondroblasts  matrix: o fibres = collagen & elastin (proteins) o ground substance = chondroitin sulphate, hyaluronic acid o water  avascular – heals slowly  e.g. hyaline cartilage of trachea, ribs, ends of long bones

Describe bone

 cells = osteocytes (in lacunae), osteoblasts, and osteoclasts  matrix: o fibres = collagen o ground substance = hydroxyapatite (inorganic Ca++ and phosphate salts) and organic components e.g. proteoglycans o water o very vascular

Describe blood (as a CT)

 cells = red blood cells (RBC) + white blood cells (WBC) |  matrix (fluid) = plasma (contains fibre proteins, ground substance, water)

What are the three types of muscle tissue?

1) skeletal (striated) 2) cardiac (striated) 3) smooth (non-striated)

What are the two types of neural cells?

Neurons | Glial cells