BIO 263 Chapter Notes - Chapter n/a: Basal Lamina, Holocrine, Merocrine
Classification of Epithelia
By number of cell layers and shape of cells at the exposed surface
● Layering Classification: simple (single) or stratified
● Three shapes: squamous, cuboidal, columnar
All simple cells have the same polarity
● Very delicate, only internal where not much damage can be done
● Found where secretion, absorption, filtration are
● Because it is so thin it lessens diffusion distance/time across barrier
Stratified has two or more layers above basal lamina
● Height and shape differs by layer
● Areas subject to stress
Squamous
● Thin, flat, irregular shape
● Simple squamous is most delicate epithelium
○ Mesothelium- lines ventral cavities
○ Endothelium- lines heart and all blood vessels
● Stratified
○ Protein keratin in in body surface lining SS, it is tough and water resistant
○ Nonkeratinized will dry out unless kept moist
○
Columnar Epithelia
● Hexagonal cross sections, height is greater than the width, nuclei in narrow band
● Simple columnar found where absorption/secretion occur, stomach, intestinal tract,
uterine tubes
Secretion
● Exocrine glands- discharge secretions on surface of skin or internal lining that
communicates with exterior through a duct
● Enzymes entering digestive tract, perspiration on skin, milk produced are all examples
○ Serous glands: secrete watery solution with enzymes: i.e. salivary amylase in
saliva
○ Mucous glands: mucins absorb water to make slippery mucus: i.e. mucus in
saliva
○ Mixed exocrine glands: contain more than one type, can produce two different
secretions
● Endocrine glands: exocytosis from gland cells, hormones diffuse in body to distribute
Unicellular glands: goblet and mucous, found scattered
Multicellular: secretory sheet: release secretion into inner compartment
● Described by shape of secretory part of gland and the branching pattern of the duct
○ Tubular glands: arranged as tube
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○ Alveolar: cells in a blind pocket
○ Combination: tubuloalveolar or tubuloacinar
○ Duct is simple with no branch, is compound with many branches
Merocrine secretion (separate), apocrine secretion (off), holocrine secretion (entire)
Connective Tissues: never exposed to environment outside body: Bone, fat, blood
1. Specialized cells
2. Extracellular protein fibers
3. Ground substance
● Almost all extracellular matrix
● Establish framework
● Transport fluid
● Provide organ protection
● Support, surround, interconnect other tissues
● Storing energy, lipids
● Defend from microorganisms
Classifications of Connective Tissue:
1. Connective Tissue proper
a. Many types of cells and extracellular fibers in syrup
2. Fluid connective tissues
a. Suspended in watery matrix w proteins
b. Blood and lymph
3. Supporting connective tissues
a. Closely packed fibers
b. Cartilage and bone
c. Matrix of bone is “calcified”
Connective Tissue Proper
Fixed cells: stationary, local repair and maintenance, energy store
● Mesenchymal: produce daughter cells in response to injury and infection
● Fibroblasts: abundant, slender, star-shape, produce connective tissue fibers
○ Manufactures and secretes proteins that form extracellular fibers
○ Secretes hyaluronan
● Fibrocytes: second most abundant, maintain connective tissue fibers and matrix
● Fixed Macrophages: scattered among fibers, engulf damaged/dead cells, defense
● Adipocytes: adipose cells, store lipid reserve
● Melanocytes: melanin store/production
Wandering cells: defense and repair of damage tissue, number of cells varies
● Free Macrophages: phagocytic cells, circulate blood as monocytes
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Document Summary
By number of cell layers and shape of cells at the exposed surface. Very delicate, only internal where not much damage can be done. Because it is so thin it lessens diffusion distance/time across barrier. Stratified has two or more layers above basal lamina. Endothelium- lines heart and all blood vessels. Protein keratin in in body surface lining ss, it is tough and water resistant. Nonkeratinized will dry out unless kept moist. Hexagonal cross sections, height is greater than the width, nuclei in narrow band. Simple columnar found where absorption/secretion occur, stomach, intestinal tract, uterine tubes. Exocrine glands- discharge secretions on surface of skin or internal lining that communicates with exterior through a duct. Enzymes entering digestive tract, perspiration on skin, milk produced are all examples. Serous glands: secrete watery solution with enzymes: i. e. salivary amylase in saliva. Mucous glands: mucins absorb water to make slippery mucus: i. e. mucus in saliva.
