KIN 216 Lecture Notes - Lecture 4: Basal Lamina, Epithelium, Anal Canal

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26 Feb 2020
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KIN 216
Outline of Tissue Types
I. Epithelial tissue: Usually is coverings, linings, exocrine glands (very little matrix).
Always have one free surface exposed to a body cavity, lumen (hollow portion of
tube), or skin surface.
Functions- Form coverings, linings of tubes and cavities. Absorption, secretion,
protection, filtering, ion transport, control permeability, provide sensations.
Key Characteristics- Cellularity, Specialized contacts with other cells, Polarity:
one side exposed (apical); unexposed side (basal) is bounded by basal lamina.
Basal lamina: thin, non-cellular sheet made up of proteins, acts as filter and
serves as scaffolding for new cell generation (has clear layer and dense layer).
**No direct blood supply (avascular) to Epithelial tissue, connective can give
blood to epithelial.
a. Membranous
i. Simple: one cell layer (all cells in layer have same shape); shape
indicative of function.
1. Simple squamous: Wide cells (more wide than tall); diffusion/
filtration
a. Single layer of flat cells
b. Occurs wherever items need to pass through quickly
c. Slippery
d. Two special types
i. Endothelium (Lines blood vessels & heart)
ii. Mesothelium (Lines body cavities on ventral side)
2. Simple cuboidal: Same height and width (cubes); secretion/
absorption
a. Single layer of cube-like cells
b. Walls of small ducts of glands, tubules of kidneys
c. Functions are limited protection, absorption, secretion
3. Simple columnar: Tall cells (taller than wide); secretion/ absorption
a. Single layer of tail cells
b. Lines digestive tube (stomach to anal canal)
c. Molecule movement; more protection than simple cuboidal
d. Some have cilia to assist with movement of substances
4. Pseudostratified columnar: Single layer but cells are different
heights (only the tall cells reach apical surface); secretion/absorption
a. Similar to simple columnar
b. i.e. respiratory tubes
c. Still one cell layer
ii. Stratified: multiple layers (cell shapes can differ among layers); named
according to apical layer (unbound); protection.
1. Stratified squamous: Many layers- surface are squamous
a. Lower levels are cuboidal or columnar
b. Thickest; best protection- epidermis of skin
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**whatever shape is on apical side is what we call it.
2. Stratified cuboidal/Columnar:
a. Rare
b. Ducts of glands
c. Not huge difference b/w these
d. Not entirely common especially columnar
3. Transitional: Similar to stratified squamous and stratified cuboidal
a. Specific to hollow urinary organs (bladder)
b. Stretches to different cell layer thickness
b. Glandular
i. Exocrine (local activity)
1. Unicellular
a. Goblet Cell; epithelial lining of intestines, respiratory tubes,
between columnar cells; produce mucin: glycoprotein that
dissolves in water=product of mucin and water is mucus
2. Multicellular
a. 2 parts: ducts and secretory unit
b. classified by duct structure:
i. simple: unbranched duct; (simple branched exist)
ii. compound: branches
iii. secretory unit: tubular (unit forms tubes) or alveolar
(spherical sacs)-tubuloalveolar also exist (contain both
tubular and alveolar units
ii. Endocrine
a. ductless; secrete into tissue fluid, go throughout body, produce
hormones
II. Connective tissue
a. Embryonic
i. undifferentiated
ii. primarily in embryo
b. CT proper
i. Loose
1. Areolar
a. location: hypodermis, fascia, surrounding nerves, blood
vessels
b. structure: loosely arranged fibers, widely spaced cells, has all
3 protein fiber types; lots of open spaces with no cells or fibers
c. function: cushioning, support and bonding, defense against
infection, nourishment of surrounding tissue-also repair of
damaged tissue
d. good blood supply; highly vascular
e. cells are mostly fibroblasts (produce protein fibers), some
mast cells; react to injury-produce heparin, which is
anticoagulant-also produce histamine, which is vasodilator
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