BIOL 1410 Histology

LECTURE 7

What is a tissue?

Group of cells with similar structure and function

What are the cells of most tissues surrounded by?

ECF called interstitial fluid (ISF)

What does ISF consist of?

Mostly water and ions

What are the 4 major types of tissues?

Epithelial, muscle, nervous, connective (CT)

What are cell junctions? What are they formed by?

Points of contact between adjacent cells formed by cell membrane proteins

In what type of tissue can cell junctions be found?

Epithelial tissue, some nervous and muscle cells

What are the 3 types of cell junctions?

tight junctions, gap junctions, desmosomes (anchoring junctions)

What do tight junctions do?

Prevent material from passing between cells, stops integral proteins from moving between apical and basolateral surfaces of the cell

What does apical mean?

“Lumen exposed surface"

What do desmosomes do?

Proteins that fasten cells to each other and/or extracellular materials

What are gap junctions?

Cytoplasmic tunnels through adjacent cells, allows for ions and small molecules to pass from cell to cell

Which type of junction is important in cardiac and smooth muscle?

Gap junctions

What is the main function of the 4 major tissue types?

Epithelial (lining), connective (connecting), muscle (contractile), nervous (sensation/signalling)

What does epithelial tissue line?

Body/organ cavities

Characteristic of epithelial tissue (4)

1 free surface, little space between cells, avascular, basement membrane

What does avascular mean

No blood vessels

What are the 2 classification “methods” for epithelial tissue?

1) # of cell layers on basement membrane (1 layer = SIMPLE, >1 layer = STRATIFIED)

2) shape of cells in the apical layer/free surface (flattened = SQUAMOUS, cube/round = CUBOIDAL, rectangular = COLUMNAR)

What would you name epithelial tissue that is 1 layer of squished/flat cells?

Simple squamous

What is the pre-dominant subtype of stratified epithelia?

Stratified squamous

What is pseudostratified epithelia?

Columnar cells that appear stratified, but all cells sit on the basement membrane (characteristic of simple epithelia!)

What is transitional epithelia?

cell shape (and layering) that varies with stretching

In transitional epithelia, “stretching” refers to cells going from cuboidal to?

Squamous

Where is transitional epithelia found?

ONLY in inner lining of urinary system

What does simple epithelia allow for?

Exchange of molecules… absorption/secretion

What is the function of glandular epithelium?

Secretion

When is epithelium called glandular rather than the typical 2 part naming system?

When epithelial tissue forms a gland

What are the 2 subtypes of glandular epithelium?

Exocrine glands, endocrine glands

What do exocrine glands do? Names of the 2 further subtypes?

Excrete products onto surface or into body cavities, unicellular/multicellular.

Function of unicellular exocrine glands

secrete MUCUS (into cavities)

Function of multicellular exocrine glands

Secretory and duct cells

What do ducts do?

They are tubes that connect secretions to surface/cavity

What do endocrine glands do?

do NOT have ducts, but secrete hormones into ECF surrounding glandular cells

Overview: What are the 3 main functions of epithelia?

Protection (often stratified squamous), secretion (glandular), and allows for selective passage of materials across membranes

Cells in connective tissue (CT) are far apart, separated by ___________ _______ that forms the bulk of the tissue

“Extracellular matrix”

cell names ending in -BLAST ______ the matrix

“create”

cell names ending in -CYTE ______ the matrix

“maintain”

cell names ending in -CLAST ______ the matrix

“break down”

What are the two components of the matrix composition of CT?

Fibres and ground substance

What are fibers made of?

Proteins

What are the 3 types of fibres in CT?

Collagen fibres, elastic fibres, reticular fibres

Function of collagen fibres

Strength

Function of elastic fibres

Contains elastin for stretch and recoil

Function of reticular fibres

Form networks (e.g. CT part of basement membrane)

What is ground substance composed of?

Water (ISF and organic molecules)

What are the four subdivisions of classification for CT (mainly by matrix composition)

Connective tissue proper, cartilage, bone, blood

What are the names of the cells in Connective Tissue Proper?

Fibroblasts/fibrocytes except adipose tissue (adipocytes)

Connective Tissue Proper has what 2 subdivisons?

Loose and Dense

Two subdivisions of loose CT

areolar CT and adipose CT

Composition and vascularity of areolar CT

loosely arranged collagen and elastin fibres, highly vascular

Matrix, type of cells and vascularity of adipose CT

Very little matrix, large adipocytes store triglycerides, highly vascular. (looks like chicken wire)

Matrix composition and vascularity of dense CT

Fibrous, little ground substance, poorly vascular

What are the two subdivisions of dense CT?

Regular and irregular

What is meant by regular/irregular in relation to the structure of tissue?

Regular - Collagen fibres running in same direction

Irregular - collagen fibres arranged irregularly

What is an example or two of dense CT in the body?

E.g. tendons and aponeuroses, ligaments

What’s a major example of dense irregular CT?

E.g. dermis of skin

What are the types of cells found in cartilage?

Chondrocytes and chondroblasts

Where are chondrocytes specifically located?

In cavities in the matrix called lacunae

What is the matrix composition of cartilage?

Fibres (collagen and elastin), ground substance is mostly water but firm due to the types of organic molecules present.

Is cartilage avascular?

Yes

What are the 3 types of cartilage?

Hyaline, Elastic, Fibro (try to remember HEF)

What is the most abundant form of cartilage?

Hyaline cartilage

Provide an example of hyaline cartilage

E.g. trachea, ribs, end of long bones

Provide an example of elastic cartilage

E.g. epiglottis, ear pinna

What is the “main function” of fibrocartilage?

“Shock absorbers”

Provide an example of fibrocartilage

E.g. invertebral discs

What are the types of cells found in bone called?

Osteocytes (in lacunae), osteoblasts, and osteoclasts.

I’ve been seeing a pattern lately of certain cell name endings for cells in lacunae. What is the cell name ending for them?

“-CYTES”

Matrix composition of bone

Fibres (abundant collagen), ground substance (inorganic calcium/phosphate salts and organic substances make it rigid). Little water.

Is bone very vascular?

Yes

What is the fluid CT type called?

Blood

What cells make up blood?

RBCs, WBCs, and platelets

What is the name of the extracellular matrix in blood?

Plasma

Matrix composition of blood

Soluble fibres, ground substance is mostly water w/ ions, proteins

What is a major example of soluble fibres in blood plasma?

E.g. fibrinogen for blood clotting

What are the 3 subtypes of muscle tissue?

Skeletal, cardiac, and smooth

2/3 subtypes of muscle tissue are striated. Which subtype is non-striated?

Smooth muscle tissue

What are the two cells found in nervous tissue?

Neurons and glial cells

Which nervous tissue cell conducts electrical impulses

Neurons

What is the purpose of glial cells?

To support and protect neurons