medical school histology basics epithelium and junctions vibs 289 lab larry johnson texas a&m...
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Medical School Histology Basics Epithelium and junctions
VIBS 289 lab
Larry Johnson Texas A&M University
Epithelium - function• Epithelium forms the outer protective surface of the
body and all the glands. It lines the walls of most closed cavities of the body and all passages leading to the exterior, and it lines blood and lymphatic vessels.
skin gland kidney cavities bladder vessels
Epithelium - function Epithelial tissues participate in the metabolism of the body through: i) the absorption of substances from the exterior, e.g., from the lumen of the intestines; and ii) the elimination of other substances to the outside. All substances, including gases, normally received and given off from the body must pass through epithelia. For the performance of secretory functions, the epithelial tissues form specialized structures called glands.
Intestine Sweatgland
Origin and Distribution of Epithelium
Ectoderm - epidermis of skin and epithelium of cornea together covers the entire surface of the body; sebaceous and mammary glands
Endoderm - alimentary tract, liver, pancreas, gastric
glands, intestinal glands• Endocrine glands - lose
connection with surface
Mesoderm• Endothelium - lining of blood vessels• Mesothelium - lining serous cavities
ECTODERM
ENDODERM
MESODERM
CLASSIFICATION OF EPITHELIA
NUMBER OF LAYERS– SIMPLE - ONE LAYER– STRATIFIED - MORE THAN ONE LAYER
SHAPE OF SUPERFICIAL CELLS– SQUAMOUS - FLAT– CUBOIDAL - CUBE– COLUMNAR – COLUMNOTHER– PSEUDOSTRATIFIED - NOT TRULY
STRATIFIED– TRANSITIONAL - URINARY TRACT
Slide 109: Skin, hand, monkey
Simple squamous endothelial cells lining blood lymph vessels– Stratified squamous epithelium of skin– Stratified cuboidal of sweat ducts
Stratified cuboidal
dermis
dermis
epidermisSweat gland
32409 Rat intestine Smooth muscle
Small intestinal villi
Simple columnar epithelium
Goblet cells
148
EM 3: region of basal lamina and connective tissue beneath intestinal epithelial absorptive cells
1. Plasma membrane
2. Basal lamina
3. Connective tissueGoblet cell
Intestinal absorptivecell nuclei
Brush border
32409EM 3
EM 3: Intestine(Basal part of cell)
Basal lamina
Intestinal absorptivecellsConnective
tissue
148
Slide 258: Kidney (PAS)
Basement membrane of epitheliumSimple squamous epithelium
Simple cuboidal in medulla and cortex
Ileum148
Simple columnar epithelium
Intestinal absorptive cells and goblet cells
Goblet cells
Brush border
Ileum, monkey (PAS)249
Basement membrane of epitheliumSimple columnar epithelium
Goblet cells
Brush border
Connective tissue
Cell nuclei
Basement membrane, brush border and goblet cells are PAS positive for sugars
EM 10f
The basal lamina of epithelial cells usually is thin (EM 10f); however, under pathological conditions, it is thickened as in the lymphatic vessel and seminiferous epithelium (Sertoli cell) of an aged-rat testis (EM 8h).
EM 8h
basal lamina
SPECIALIZATION OF EPITHELIA
MAINTAIN EXTENSIVE CONTACTS AMONG CELLS
STRUCTURALLY AND FUNCTIONALLY POLARIZED
JUNCTIONSZONULA OCCLUDENS - TIGHT JUNCTION (BELT)ZONULA ADHERENS –
ADHERING BELTDESMOSOME (MACULA
ADHERENS) - SPOT ATTACHMENTGAP JUNCTIONS - COMMUNICATION
Terminal bars
32409
148 250
250
32409
Terminal bars
Terminal bars are part of a belt (zonula)around the cells.
belt
Intestinal absorptive cells
Goblet cells
EM 4: Intestine (Apical)
Tight junction, zonula adherens,
terminal web
148
Goblet cells
EM 2: Liver
– Gap junction,– desmosome,
tight junction
EM 2a: Liver- Gap junctions
EM 2
133133
250
Simple squamous epithelium cellsviewed on their sides
vein
Lumen of lymphatic vessel
valve
valvecapillary
Simple squamous epithelium cellsviewed “face on”
venule
Simple squamous epithelium
Lumen of lymphatic vessels
arteriole
valve109
19680testis
196
valve
vein
capillary
EM 10A showing capillary endothelial cells109
Simple squamous epithelium : cellsviewed on the side
Stratified squamous epithelium 109
Keratinized dead flattered cells at surface
Slide 109: Skin, hand, monkeyprickle cell" layer (desmosomes)
dermis
epidermis
Slide 109 : Skin, hand, monkey
Stratified cuboidal is only found in sweat ducts of skin (Slide 109).
Fat cells
epidermisdermis
HISTO052 tongue Vagina (Slide 178)
non-keratinized stratified squamous epithelium
Nuclei present in flat cells at surface
Slide 133: Trachea, monkey
– Simple squamous lining the air spaces of lungs
– Pseudostratified epithelium lining tracheal lumen
– Ciliated epithelium of trachea, goblet cells, thick basement membrane
Lungair space
432
133
tracheal lumen (Slide 133),
transition of the luminal epithelium from stratified squamous of vocal cords to pseudostratified, ciliated epithelium
human larynx, Slide 429
stratified squamous
Note thickened basement membrane typical of this epithelium
pseudostratified, ciliated epitheliumcalled respiratory epithelium
Plasma cells133
Transitional epithelium urinary bladder (Slide 160) ureter (Slide 262)
Slide 160 Image of the Urinary bladder
Transitional epithelium
Mesothelium
Lumen of bladder
HISTO052 (tongue) to observe mucus and serous glands
In summary
All substances, including gases, normally received and given off from the body must pass through epithelia.
Which junction - description pair match?a. Zonula occludes – tight junction around the cellb. Zonula adherens – adhering junction around the cellc. Hemidesmosome – spot attachment of cells to the CT belowd. a & be. a, b, & c
Which item(s) is/are characteristic of epithelia?a. secretory cells of glandsb. covers organsc. line urinary tractd. a & be. a, b, & c
Questions on Epithelia
Which embryonic origin - distribution of epithelium do not match? a. endoderm - endothelium b. endoderm - alimentary tract c. mesoderm - mesothelium d. ectoderm - mammary gland e. ectoderm - epidermis
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Many illustrations in these VIBS Histology YouTube videos were modified from the following books and sources: Many thanks to original sources!
Ranch just south of Fort Stockton, TX
On road from Fort Stockton to Big Bend National Park, TX
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