L2 - Epithelial Tissue Flashcards
What is the function of epithelial tissue?
Covers body surface
lines hollow organs, cavities and ducts
Forms the glands of the body
What is the cytoskeleton composed of?
Microfilaments such as actin
Intermediate filaments such as keratin
Describe the structure of tight junctions
Strands of transmembrane proteins (claudins and occludins) link adjacent plasma membranes in a ‘sew-like’ appearance
What is the function of tight junctions
Joins the cytoskeleton of adjacent cells
Keeps cell polarity by preventing migration of proteins between apical and basal surfaces
Where are tight junctions primarily found?
Stomach, intestines, bladder
Describe the structure of adherens junction
Two plaques (patches of protein tissue) on each membrane linked together by cahderin
Cadherin links to catenins which links to actin
What is the function of adherens junction
Links the microfilaments of adjacent cells preventing cell separation from tension forces like muscle contraction
Describe the structure of desmosome junctions
Composed of two plaques joined together by cadherin
Cadherin spans the gap and binds to Desmoplakin which links to keratin
Function of desmosome junctions
Links the intermediate filaments of adjacent cells providing strength to the junctions between cells
Allows tissue to resist shearing forces
Where are desmosome junctions found
They bind muscle cells; most common in skin epithelium and cardiac cells of the heart
Describe the structure of gap junctions
6 ConnexIn protein molecules to make a ConnexOn / hemichannel
2 hemichannels make up a gap junction
Function of gap junctions
Allows cells to communicate with one another
Transfer of ions and small molecules between adjacent cells of tissue
Describe the structure of hemidesmosomes
A plaque is connected to the basement membrane via Integrin Integrin acts as linker protein between keratin of the basal layer cell and laminin in the BM
Function of hemidesmosomes?
Prevents movement of the epithelial layer over the basement membrane; fixation of cell
What does the junctional complex include
Tight junction, Adherens junction, desmosome
What is the function of the basement membrane?
Supports the overlying epithelium
Provides a surface along which epithelial cells migrate during growth and wound healing
Acts as a physical barrier
Participates in the filtration of substances in the kidney
What are the two types of glandular epithelia?
Endocrine - secretes hormones into blood (more distant strong effects)
Exocrine - secretion onto external surfaces and ducts (more local effects)
What is endothelium?
Simple squamous epithelium lining the inside of the heart, blood and lymphatic vessels (CARDIOVASCULAR SYSTEM and LYMPHATIC SYSTEM)
What is mesothelium?
Simple squamous epithelium lining the serous membranes of the heart, lungs and abdominal areas
What are examples of where simple squamous epithelium is found?
In Bowman’s capsule of kidney, cardiovascular
and lymphatic systems, inside eye, alveoli of lungs, visceral cavity linings, inside blood vessels and inside heart
Where is simple cuboidal epithelium found?
Where there is SECRETION and ABSORPTION
Pancreas ducts, parts of kidney tubules, smaller ducts of many glands, secretory chambers of thyroid; anterior surface of lens; pigmented epithelium at posterior of retina; secretory part of some glands like thyroid
What are microvilli
Finger-like projections from the membrane that increases surface area for absorption and exchange of materials
What are cilia
Short hair-like projections from columnar epithelia cells that can act in a sweeping motion to move substances along surfaces
Where is non-ciliated simple columnar epithelium found?
GI tract from stomach to anus, ducts of many glands, gallbladder
Where is ciliated simple columnar epithelium found?
some bronchioles, uterine fallopian tubes, sinuses; central canal of
spinal cord, ventricles of brain
What are the features of keratinised stratified squamous epithelium?
Contains kertain making surface tough and waterproof
Found in skin
What are the features of non-keratinised stratified squamous epithelium?
Do not contain kertain therefore lines wet surfaces such as mouth, oesophagus, vagina, pharynx and tongue
Moistened by mucous
What are the features of pseudostratified columnar epithelium
All cells touch the basement membrane but not all cells reach the apical surface
Can be ciliated or non-ciliated
What is the difference between ciliated and non-ciliated pseudostratified columnar epithelia?
Ciliated has goblet cells
Non-ciliated has no goblet cells
Therefore ciliated lines most of upper airways and non-ciliated lines larger ducts of glands, epididymis, part of male urethra
Where are ciliated pseudostratified columnar cells commonly found?
most of upper airways
Where are non-ciliated pseudostratified columnar cells commonly found?
larger ducts of glands, epididymis, part of male urethra
What are the features of stratified cuboidal epithelium?
Usually for protection - limited secretion and absorption
Found in ducts of sweat glands and oesophageal glands
What are the features of stratified columnar epithelium?
Proection and secretion
Found in part of urethra, large excretory ducts of some glands, small areas in anal mucous membrane
What are the features of transitional epithelium?
Looks like stratified cuboidal epithelium
Outer layer is large, round (scallop shaped) when relaxed
On stretching, outer layer become flat and squamous like
Found in urinary bladder (only)
Name the different shapes of multicellular ducts (8 total)
Simple tubular
Simple coiled tubular
Simple branched tubular
Simple alveolar
Simple branched alveolar
Compound tubular
Compound alveolar
Compound tubuloalveolar
Example of simple tubular glands
Intestinal glands
Example of simple coiled tubular glands
Merocrine sweat glands
Example of simple branched tubular glands
Gastric glands
Mucous glands of oesophagus, tongue, duodenum
Example of simple alveolar glands
A stage in the embryonic development of simple branched glands
Example of simple branched alveolar glands
Sebacous (oil) glands in the skin
Example of compound tubular glands
Mucous glands (in mouth)
Bulbo-urethral glands (in male reproductive system)
Seminiferous tubules of testes
Example of compound alveolar glands
Mammary glands
Example of compound tubuloalveolar glands
Salivary glands
Glands of respiratory passages
Pancreas
