Anatomy and Physiology chapter 4 - histology
Histology - the study of tissue
Basic functions of epithelial tissues -
... [Show More] protection
Absorption
Filtration
Excretion
Secretion
Sensory reception
Special characteristics of of epithelium - 1. Cellularity - closely packed cells
2. Specialized contacts - demosomes (anchors cells together); tight junctions (form impermeable layers); gap junctions (communication)
3. Polarity - apical surface (faces free space); basal surface (closer to basal membrane)
4. Supported by connective tissue - areolar connective tissue (reticular lamina lies below basal lamina and secreted by connective tissue)
5. Avascular but innervated
6. Regeneration
Basement membrane - basal lamina + reticular lamina of connective tissue
Resists tearing and stretching forces
Defines epithelial boundary
Simple squamous epithelium - structure: single layer of flat cells; nuclei often seen as bumps
Function: diffusion, filtration
Location: lungs, kidneys, and blood vessel walls, serous membranes
Simple cuboidal epithelium - structure: single layer, cube shaped, some have microvilli
Function: secretion and absorption
Location: kidney tubules and glands
Simple columnar epithelium - structure: single layer of tall, narrow cells
Function: secretion and absorption, movement of particles
Location: lines digestive tract
*microvilli and goblet cells
Pseudostratified columnar epithelium - structure: 1 cell thick, looks stratified, nuclei at different levels (none at apical side), cilia
Function: secretion and absorption, secrete mucus
Location: respiratory tract
Stratified squamous epithelium - structure: multiple layers, cube shaped in basal layer and progressively flattened towards apical layer
Function: protection against wear and tear
Location: skin, anus, nose, esophogus
Stratified cuboidal epithelium - structure: multiple layers, cube shaped
Function: secretion
Location: sweat glands and mammary glands
Stratified columnar epithelium - structure: multiple layers with tall, thin cells
Function: protection, secretion
Location: glands, male urethra, pharynx, and transitional areas
Transitional epithelia - structure: multiple layers; cube shaped when not stretched and squamous when stretched
Function: accommodate fluctuations in amount of fluid
Location: lining of urinary organs
Gland - consists of one or more cells that make and secrete a product (goblet cell = gland)
Glandular epithelia - endocrine glands - ductless that secrete hormones into the blood (not lined with glandular epithelium)
Exocrine glands 0 secretes products onto body surfaces or into body cavities (using a duct)
Types of glandular epithelia - unicellular exocrine glands - goblet cells
Multicellular exocrine glands - 2 parts; acini cells - secretory cells of gland, duct cells - form a duct for passage of product onto surface or body cavity
3 modes of secretion - merocrine glands - exocytosis (sweat glands, salivary glands)
Holocrine glands - accumulate products until they rupture; constant mitosis
Apocrine glands - excrete by pinching off apical portion of the cell (mammary glands)
4 main classes of connective tissue - connective tissue proper
Cartilage
Bone
Blood
Four main functions of connective tissue - binding and support - tendons
Protection - immune system
Insulation and cushioning (fat)
Transportation - blood
Storage (fat) [Show Less]