Chapter 5 Tissue
Outline
Definition: Tissue is a group of similar cells and cell products that arise from the same
region of the embryo and work together to perform a specific function.
Tissue sections: histological sections and can be longitudinal, cross section or transverse
section and oblique section. See page 143.
Four types of tissues---epithelial, connective, muscle, nervous
1. Epithelial tissue function: protection, secretion, excretion, filtration and sensation.
Epithelium:
- Covering and lining epithelium
- Glandular epithelium
Characteristics of epithelium:
- Closely packed cells
- Cell to cell contacts---tight junctions and desmosomes
- Polarity--- apical and basal surface
- Supported by connective tissue
Classification of epithelium:
On the bases of structure (shape of cells) and function (number of layers)
Number of layers:
One layer of cells--- simple
More than one layer of cells--- stratified
Shape of the cells:
Squamous---flat, scale like --Cuboidal---cube or box like
Columnar---tall and column like
Combined classification: function with structure
a). Simple squamous epithelia --- for absorption, secretion and filteration e.g. wall of
glomerular capsule. Air sacs
Special names to certain simple squamous epithelia
- Endothelium--- inner covering e.g. lymphatic vessels, blood vessels
- Mesothelium --- middle covering e.g. in serous membranes lining of body cavity
b). Simple cuboidal epithelia --- secretion and absorption e.g. kidney tubules
c). Simple columnar epithelia --- absorption and secretion e.g. lines the digestive tract--some modified into goblet cells
d). Pseudostratified columnar epithelia --- vary in height but all rest on the basement
membrane e.g. trachea
e). Stratified squamous epithelia --- wear and tear, protection e.g. skin
f). Stratified cuboidal epithelia --- secretion e.g. sweat glands
g). Stratified columnar epithelia --- male urethra
h). Transitional epithelia --- stretch e.g. lining of hollow urinary organs--- basal cells
cuboidal or columnar, apical cells --- squamous
Glandular epithelia:
Exocrine glands --- with ducts
Endocrine glands --- ductless
2. Connective tissue Definition: Mostly binds one organ to each other.
Connective tissue functions: binding organs (tendon bind muscle to bone); support
( bones support the body, cartilage support the ear); physical protection (cranium, ribs);
immune protection(connective tissue cells attack foreign invaders) ;movement (bones as
lever system of body; storage (fat); heat production (metabolism of brown fate generate
heat in infant and children) transport (blood transport gases). See page 150-151.
characteristics:
common origin--- mesenchyme
extracellular matrix --- mostly made up of ground substance
Structural elements:
Ground substance-proeoglycan, glycosaminoglycan (chondroitin sulphate, hyaluronic
acid)
Fibers-collagen, reticular and elastic.
Cells-fibroblast, macrophages, leukocytes, mast cells, plasma cells, adipocytes.
Types of connective tissue:
i)
Embryonic connective tissue: mesenchyme ,mucous connective tissue
ii)
Connective tissue proper--- two subclasses
a) Loose connective tissue
b) Dense connective tissue-dense regular ( collagen fibers closely
packed in regular manner and dense irregular (bundles of
collagen fibers arranged irregularly (most of dermis)
Loose connective tissue
Areolar
Adipose
Reticular
Dense connective tissue
Cartilage
Bone
Blood
Covering and lining membrane
cutaneous
mucous
serous
3. Nerous tissue:
- Neurons
- neuroglia
4. Muscle tissue:
- Skeletal
- Cardiac
- smooth