Epithelium Gland

8/7/2019 Epithelium Gland

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General

� Tissues - groups of cells with similar basic structureswhich cooperate to perform a related function

� Four basic types of tissues± Epithelial linings for protection, coordination, synthesis,

absorption, elimination

± Connective support

± Muscle for movement� muscle tissue is a highly specialized connective tissue

± Nervous for control and coordination� nervous tissue is a highly specialized epithelial tissue



Epithelial Tissue Characteristics

1. Cellularity - densely packed

2. Polarity� apical surface

� basal surface (or basolateral)

3. Specialized contacts - tight junctions anddesmosomes

4. Supported by connective tissue� basal lamina (epithelial glue)

� reticular lamina (connective tissue glue)

� basement membrane - reticular and basal laminae together

5. Innervated but avascular (no direct blood supply)

6. Regeneration high capacity for regeneration



Simple

Stratified

Classifying Epithelial Tissues

� B

ynu

mber of cell layers

Pseudostratified epithelium (from the respiratory

tree) appears stratified, but actually is a single

layer of cells of varying heights; each cell touches

the basement membrane



Classifying Epithelial Tissues

± By cell shape

Transitional

Squamous

Columnar

Cuboidal



Glandular Epithelial Tissues

� functions in secretion a gland may be one cellor a group of specialized cells

� two major types±

exocrine glands have ducts leading to body surfaces� various products are synthesized and stored for release

� secretions are secreted into the duct system

� e.g., sweat glands, salivary glands, etc.

± endocrine glands are ductless� hormones are synthesized and stored for release� hormones are secreted into the tissue fluid and then diffuse

into the blood stream

� e.g., thyroid and parathyroid glands



Exocrine Gland Classification

� Unicellular glands

± single cell glands

� goblet cells

� neuroendocrine cells

goblet cell



Exocrine Gland Classification� Multicellular glands

± Structurally classified byduct configuration and

by the shape of the

secretory units

� simple glands have a

single duct

� compound glands have

branched ducts

± Merocrine glands

� Exocytosis

± Holocrine glands

� Cell rupture



Types of Glands

Exocrine: all glands with ducts

Endocrine: ductless glands (hormones)



Apocrine Glands

� top of cell pinches off releasing contents

� some sweat glands (armpits and groin)

�

cause scent when fatty acids and proteins insweat metabolize

� become active at puberty

� Why do guys smell worse?



Merocrine Glands

Merocrine (eccrine): secretion by exocytosis

� Salivary glands and sweat glands (temp reg)



Holocrine Glands

Holocrine: cell ruptures releasing contents

� sebaceous glands

� sebum



Sweat Facts

The average person had 2.6 million sweat

glands in their integument.

There are sweat glands distributed over the

entire body---except the lips, nipples, and

external genitalia.



MucousMembranes

Mucous

± Line cavities open to exterior (nose, mouth, etc)

±

Often secrete mucous



Serous Membranes

Occur in pairs

»Visceral: lines organs

»Parietal: lines body cavities

used to avoid friction

lines cavities closed to exterior

secrete serous fluid lubricant





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Epithelium Gland