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Glossary of Anatomy CH.3

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Tissues
Collections of specialized cells and their cell products that perform specific functions based on tissue type
4 types of tissues
1. epithelial
2. connective
3. muscle
4. neural


Histology
study of tissue
Epithelial Tissue
tissue which covers surfaces, lines body cavities, and forms glands

-includes epithelia and glands

6 characteristics of epithelia
1. consists of tightly joined cell groups that are polarized
2. apical surfaces face some environment
3. bottom surfaces anchored to basal lamina
4.lateral surfaces meet other cells of same type
5. cells are continuously being replaced (by mitosis)
6.are an avascular layer of cells




Characteristics of Epithelia

-from outline

1. composed of closely bound cells--by cell junctions
2. has an exposed surface-apical surface and basal surface- attached to underlying tissue
3.attached to basement membrane/basal lamina
4. does not contain blood vessels--avascular (without blood supply)
5. cells are continually replaced by mitosis





Functions of Epithelium Tissues
1. provides physical protection
2. controls permeability
3. provides sensation by detecting changes in the environment and sending this information to the nervous system
4. produces specialized secretions thru the formation of glands (glandular cells)


Specialization of Epithelia
-production of secretions by organelles

-on exposed surface of cell:
1.microvilli: involved in absorption, increases surface area--look like teeth on a comb
2.cilia: beat and move substances along surface
3.stereocilia: long microvilli; they branch but don't move; primarily actin; only in male reproductive system

-movements of fluids over surface by beating of cilia






Maintenance of integrity of epithelium
-intercellular connections

-attached to basement membrane which is 2 layers
-basal lamina: epithelium actually attaches to it
-reticular laminae: gives strength to epithelium

-maintenance and repair: depends on stem or germinative cells present





Classification of Epithelia is based on:
1. number of cells in the epithelial layer
2. shape of surface layer of cells
Types of Epithelium based on number of cell in layers
simple: one layer of cells

stratified: two or more layers of cells

Types of Epithelium based on shape of the surface layer of cells
1. squamous
2. cuboidal
3. columnar

Simple Squamous epithelia
cells are thin, flat, and irregular in shape

Locations:
-in alveoli (respiratory spaces) of lungs
-serous lining of body cavities and on surface of organs- mesothelium
-lines inner surface of vessels (vascular system)- endothelium
-Bowman's capsule (kidney)





Simple cuboidal epithelia
occur in regions of secretion and absorption

Locations:
1. small ducts of exocrine glands
2. surface of ovary (germinal epithelium)
3. kidney tubules
4. thyroid follicles (glands)
5. lines ducts of salivary glands
6. pancreas--secretion









Simple Columnar epithelia
Locations:
1. small intestine
2. colon
3. stomach lining and gastric glands and
4. gallbladder
5. lines uterus
6. excretory ducts





Pseudostratified columnar epithelia
--simple epithelia
-found in respiratory epithelium
-has cilia therefore called pseudostratified ciliated columnar

Locations:
1. nasal cavity
2. trachea
3. bronchi (bronchial tree)
4. ductus deferens
5. efferent ductules of epididymis
6. parts of male reproductive tract









Stratified Cuboidal epithelia
very rare in humans

Locations:
1. sweat duct glands
2. large ducts of exocrine glands--mammary glands
3. anorectal junction




Stratified columnar epithelia
rare

Locations:
1. largest ducts of exocrine glands
2. anorectal junction
3. pharynx
4. urethra
5. anus
6. excretory ducts







Transitional (urothelium)
--stratified epithelia

-permits stretching

Locations: (all urinary system)
1. renal calyces (renal pelvis)
2. ureter
3. bladder
4. urethra







Stratified Squamous epithelia
-surface where there is stress
-keratinized v. nonkeratinized

Locations:
1. surface of skin (epidermis)
2. oral cavity, pharynx, esophagus
3. rectum and anus
4. vagina






Squamous Epithelium
thin, flat, and scale-like cells
Cuboidal epithelium
cells as wide as they are tall
Columnar Epithelium
cells taller than they are wide
Types of Glands
1. exocrine
2. endocrine
Exocrine Glands
-secretions discharged thru ducts onto skin or epithelial surface

1. serous: secrete watery solutions, like sweat
2. mucous: secrete mucous, sticky
3. mixed: contains both mucous and serous elements



Endocrine Glands
ductless glands secrete into extracellular fluid

-secretes hormones
-released into capillaries...no ducts
-act at a site distant from their release





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