Topic 7: Histology Flashcards
Histology
the study of tissues
Tissue
a group of cells with similar structure and function
List the 4 major tissue types:
Epithelial Tissue; lining tissue
Connective Tissue; connecting tissue
Muscle Tissue; contractile tissue
Nervous Tissue; signalling tissue
Cell Junctions
points of contact between adjacent cells - seen in epithelial tissue, some nervous and muscle cells
formed by cell membrane proteins
List 3 examples of cell junctions
1) Tight Junctions
2) Anchoring Junctions (e.g. desmosomes)
3) Gap Junctions
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)
- things don’t exit or enter
Anchoring Junctions
(e.g. desmosomes)
proteins that fasten cells to each other and/or extracellular material (“rivets” cells
together)
- hold cell close to one another
Gap Junctions
open channels (formed by proteins) through the adjacent cell membranes
interconnecting the cytosols of the cells; allows for interconnected cell
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
Epithelial Tissue
covers body surface
lines body/organ cavities
organ cavity = lumen
Characteristics of Epithelia:
o has one free surface
o little extracellular space between cells; cells are very closely packed
o avascular – no blood vessels
o Basement membrane
Basement membrane
extracellular layer
attaches epithelium to underlying CT layer (formed by both tissues – “velcro”
- Ct layer keeps epithelial tissue alive
What level of organization is the basement membrane?
Organ; b/c 2 tissues
How is epithelial tissue classified
o most subtypes are classified + named according to:
# of cell layers sitting on the basement membrane
shape of the cells in the apical layer (= layer touching the free surface)
one layer
simple
more than one layer
stratified
apical layer
= layer touching the free surface)
squamous
flattened
cuboidal
round or cube shaped
columnar
rectangular
Simple Epithelia
= 1 layer
allow exchange of molecules (gasses, nutrients, etc.)
–absorption/secretion
List the subtypes of simple epithelia
a) simple squamous
b) simple cuboidal
c) simple columnar
simple squamous
= 1 layer of squished (flat) cells
e.g. lungs
simple cuboidal
= 1 layer of cube shaped cells
e.g. kidneys
simple columnar
= 1 layer of column shaped (tall & thin) cells
e.g. stomach, small intestine
Stratified Epithelia
= > 1 layer
protective (areas of abrasion)
List the subtypes of Stratified Epithelia
a) stratified squamous
b) stratified cuboidal
c) stratified columnar
stratified squamous
= apical cells squished (flat)
common, e.g. skin
stratified cuboidal
apical cells cube shaped
rare
stratified columnar
= apical cells column shaped (tall & thin)
rare
Pseudostratified Epithelia
appears stratified (nuclei at different levels), but all cells sit on basement membrane (= SIMPLE!)
e.g. lines most of respiratory tract (+ ciliated)
pseudo= false
Transitional Epithelia
= cell shape (& layering) varies with stretching
only in inner lining of urinary system
cuboidal to squamous when stretched
List the types of Epithelial tissue
1) Simple Epithelia
2) Stratified Epithelia
3) Pseudostratified Epithelia
4) Transitional Epithelia
5) Glandular Epithelium
What happens if epithelial cells form a gland
he cell layer(s)/cell shape classification is no longer
used & tissue is classified as:
5) Glandular Epithelium
5) Glandular Epithelium
for secretion
List the subtypes of Glandular Epithelium
a) exocrine glands
b) endocrine gland
exocrine glands
secrete products onto body surface or into a body cavity
can be:
i. unicellular
ii. multicellular
unicellular exocrine glands
¦ e.g. goblet cells
¦ secrete mucus (into a cavity)
¦ in the digestive, urinary,
reproductive,
respiratory tracts
multicellular
¦ consists of secretory and duct cells (ducts
connect secretions to surface or cavity)
¦ e.g. glands: sudoriferous (sweat), sebaceous
(oil), mammary, digestive
endocrine glands
no ducts (ductless)
secretions (hormones) directly into the blood
e.g. thyroid gland secretes thyroid hormone
List 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
Connective Tissue (CT)
mainly supports and connects tissues
cells far apart, separated by extracellular matrix
o extracellular material gives CT subtypes their identifying characteristics
variable vascularity
cell names ending in
-BLAST
-CYTE
-CLAST
BLAST
– create matrix
- forming more
¦ e.g. osteoblast, chondroblast, fibroblast
CYTE
– maintain matrix; maintaining stuff around us
¦ e.g. osteocyte, chondrocyte, fibrocyte
-CLAST
– break down matrix; reabsorb material
¦ osteoclast; reabsorbing bone b/c are ca2+ resovoirs
Matrix Composition
1) Fibres (proteins)
2) Ground Substance
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)
Ground Substance
unstructured material surrounding extracellular fibres and cells
composed of water and large organic molecules (e.g. hyaluronic acid, chondroitin
sulfate)
How is CT classified
(mainly by matrix composition)
List the types of CT
- CT Proper
2) Cartilage
3) Bone
4) Blood
CT Proper
cells = fibroblasts/fibrocytes except adipose tissue (adipocytes
List the subtypes of CT proper
a) Loose CT
b) Dense CT
Loose CT
. areolar CT
¦ loosely arranged collagen and elastin fibres surrounded by ground substance (hyaluronic acid)
¦ highly vascular
¦ e.g. lamina propria
adipose CT
¦ very little matrix
¦ cells large (adipocytes), store triglycerides - tissue looks like
“chicken-wire”
highly vascular
Dense CT
many fibres (a.k.a. fibrous CT) little ground substance _poorly vascular types: i. dense regular CT ii. dense irregular CT
dense regular CT
¦ collagen fibres running in the same direction
¦ e.g. tendons, ligaments
dense irregular CT
¦ collagen fibres arranged irregularly
¦ e.g. dermis of skin
Cartilage
cells = chondrocytes (cells located in lacunae = cavities in the matrix) &
chondroblasts
matrix:
o fibres = collagen & elastin (proteins)
o ground substance =
Ø chondroitin sulphate, hyaluronic acid
Ø water
avascular – heals slowly
e.g. hyaline cartilage of trachea, ribs, ends of long bones
lacunae
cavities in the matrix
* empty space if you remove the cell
Bone
cells = osteocytes (in lacunae), osteoblasts, and osteoclasts
matrix:
o fibres = collagen
o ground substance =
Ø hydroxyapatite (inorganic Ca++ and phosphate salts) and organic
components e.g. proteoglycans
Ø water
o very vascular
Blood
cells = red blood cells (RBC) + white blood cells (WBC)
matrix (fluid) = plasma (contains fibre proteins, ground substance, water)
Muscle Tissue
contractile
subtypes:
1) skeletal (striated)
2) cardiac (striated)
3) smooth (non-striated)
Nervous Tissue
cell types:
1) neurons – conduct electrical impulses
2) glial cells – support and protect neurons
