1. Tissue: The Living Fabric4
P A R T A
Tissue: The Living Fabric

2. Groups of cells similar in structure and function
Tissues
Groups of cells similar in structure and function
Histology studies the four tissue types of the human body:
Epithelial
Covers organs and the body
Lines cavities
Connective
Binds (holds) the body together
Protection, insulation, transportation

3. Muscle
Contracts (shortens) to move the body or substances inside the body
Nerve
Sends electrical signals to control the body

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5. Epithelial Tissue
Found on the surface of the body
Covers the organ wall
Lines the body cavities
Found in the glands

6. Epithelial functions:
Forms boundaries
Protection
Absorption: allows materials in
Filtration: regulates what goes in or out
Excretion: removes wastes
Secretion: release something useful
Sensory reception: changes shape

7. Epithelial Tissue: special characteristics
1. Special contacts – it tightly fits close together to form continuous sheets
2. Polarity – it has two surfaces... A top & a bottom. Apical (top) is free and basal (bottom) is attached to something
3. Supported by connective tissue
4. Avascular but innervated – contains no blood vessels (avascular) but supplied by nerve fibers (innervated)
5. Regenerative – rapidly replaces lost cells by mitosis… (grows easily)

8. Classification of epithelium
Epithelial tissue is classified by cell shape and by how many layers of cells there are

9. Classification of Epithelia: number of layers
Simple
1 layer
stratified
Two or more layers
Figure 4.1a

10. Classification of Epithelia: cell shape
Squamous
Flattened, scalelike
Cuboidal
boxlike
Columnar
Tall, rectangular or column shaped
Stopped 2nd
Figure 4.1b

11. Epithelia: Glandular
A gland is one or more cells that makes and secretes an aqueous (water based) fluid
Classified by:
Site of product release – endocrine or exocrine
number of cells forming the gland

12. Ductless glands that produce hormones
Endocrine Glands
Ductless glands that produce hormones
Chemical messengers carried by the blood
Secretions include amino acids, proteins, and steroids

13. Exocrine Glands
More numerous than endocrine glands
Secrete their products onto body surfaces (skin) or into body cavities
Must use ducts
Examples include mucous, sweat, oil, and salivary glands