KIN 216 Lecture Notes - Lecture 4: Basal Lamina, Epithelium, Anal Canal
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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.
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/
a. Single layer of ﬂat cells
b. Occurs wherever items need to pass through quickly
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/
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
**whatever shape is on apical side is what we call it.
2. Stratiﬁed cuboidal/Columnar:
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
i. Exocrine (local activity)
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
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
a. ductless; secrete into tissue ﬂuid, go throughout body, produce
II. Connective tissue
ii. primarily in embryo
b. CT proper
a. location: hypodermis, fascia, surrounding nerves, blood
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
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