Transitional epithelium

GENERAL HISTOLOGY

CONTENTS:

Epithelia....................................................................................3

Connective tissue......................................................................15

Blood...................................................................................... 69

Muscular tissue....................................................................... 89

Nervous tissue....................................................................... 110

Sense organs.......................................................................... 140

EPITHELIUM

Epithelial tissues are formed by closely apposed polygonal cells with little or no intercellular material.

EPITHELIUM:

- SURFACE

- GLANDULAR

- SENSORY

SURFACE EPITHELIUM:	It lines the outer surface of the body and the luminal surfaces of cavities within the body.
UNILAYERED:	It consists of only one layer of cells.
- Simple:	All the cells are adjacent to the basal membrane and have equal height.
1. squamous	Its cells are flattened, their height being very little as compared to their width.
2. cuboidal	The height and the width of its cells are more or less equal.
3. columnar	The height of its cells is distinctly greater than their width.
- Pseudostratified	All the cells are adjacent to the basal membrane, but have different height. The cell nuclei lie at different level.
MULTILAYERED (STRATIFIED):	It consists of several layers of cells.
- Squamous	Superficial cells are squamous in shape.
1. non keratinized	Superficial cells are living and contain nuclei.
2. keratinized	Superficial cells are dead and are devoid of nuclei.
- Transitional	Superficial cells are able to change their form depending upon the degree of distention.

SIMPLE SQUAMOUS EPITHELIUM

SIMPLE CUBOIDAL EPITHELIUM

SIMPLE COLUMNAR EPITHELIUM

Pseudostratified epithelium

STRATIFIED NONKERATINIZED EPITHELIUM

TRANSITIONAL EPITHELIUM

GLANDS:	Epithelial cells that are specialized to perform secretory function.
UNICELLULAR	Gland that consists of one cell.
MULTICELLULAR:	Gland that consists of a lot of cells.
- Endocrine	Gland that pours its secretion into blood.
- Exocrine:	Gland that pours its secretion on to an epithelial surface, directly or through a duct.
1. simple	All the secretory cells of an exocrine gland discharge into one duct.
- unbranched	It contains one excretory duct and one acinus.
- branched	It contains one excretory duct and several acini.
2. compound	There are a number of groups of secretory cells, each group discharging into its own duct. These ducts unite to form a larger duct which ultimately drain on to an epithelial surface.

Exocrine glands consist of: - dicts; - acini.

Both in simple and compound exocrine glands the secretory cells of acini may be arranged in various ways: (a) The secretory elements may be tubular. (b) The secretory elements may form flask shaped structures called alveoli.

Exocrine glands may also be classified on the basis of the nature of their secretions into: - mucous glands; - serous glands.

Types of secretion of exocrine glands:
Merocrine type of secretion	Secretions are thrown out of the cells by a process of exocytosis the cell remaining intact.
Apocrine type of secretion	The apical parts of the cells are shed off to discharge the secretion.
Holocrine type of secretion	The entire cell disintergates while discharging its secretion.

Дата добавления: 2015-10-30