Types of Body Tissues

1 .Epithelial.

2 .Connective.

3 .Muscular.

4 .Nervous.

Epithelial tissueIt is present in two forms: 1-Epithelia (contiguous cells covering external body surfaces and lines internal cavities).

2-Glands (from invigilated epithelial cells).

Functions:

A-Protection.

B-Transcellular transport.

C-Secretion.

D-Absorption.

E-Detection of sensation.

F-Selective permeability.

Characteristics of epithelium:

1.The cells are tightly bound together by

junctional complex.

2.Is avascular.

3.Rests on basal lamina.4.Has little intercellular space and little extracellular

matrix.

5.Its cells exhibit a high turnover rate and constante cell renewal for a particular epithelium

Classification of epithelial membranes• According to the number of cell layers:I. Simple (formed of one layer of cells)

II. Stratified (formed of more than one layer of cells)

• According to the morphology of the cells:1-Simple squamous epithelium:

thin low profile polygonal cells

with central nuclei.

(ex.pulmonary alveoli, loop of

Henle, endothelium of blood

vessels, pleura and peritoneal

cavities).

2-Simple cuboidal epithelium: single layer of polygonal cells with central round nuclei (Ex. ducts of many glands and some kidney tubules)

3-Simple columnar epithelium: single layer of columnar cells with ovoid nuclei located in basal half of cells (Ex. lining of digestive tract, gall bladder and large ducts of glands)

.Or may have cilia as in oviduct, uterus, and small bronchi.

* Simple columnar epith. may exhibit goblet cells and microvilli as in intestine

4-Stratified squamous ( Non-keratinized) epithelium: Is formed of several layers of cells in which the most basal layer rests on basal lamina and it is cuboidal cells (the intermediate layers) are polyhedral or polymorphous. The most superficial layer is formed of flat squamous cells not covered with keratin (Ex.lining of mouth, oral pharynx, esophagus, true vocal cords and vagina).

5-Stratified squamous (Keratinized) epithelium: similar to non keratinized type but the superficial layer is covered with keratin (Ex. epidermis of skin specially in soles and palms)

6-Stratified cuboidal epithelium: is composed of 2-4 layers of cuboidal cells (ex. Ducts of sweat glands).

7-Stratified columnar epithelium: Is formed of more than one layer of cells with superficial columnar cells (ex. conjunctiva of the eye, large excretory ducts and regions of male urethra).

8-Transitional epithalium: is formed of many layers of cells, the basal layer is formed of low columnar or cuboidal cells, while the superficial layer is formed of large dome shaped binucleated cells (in empty bladder).

*In full bladder

the dome-shaped

cells become

flattened and

the epithelium becomes thinner.

9-Pseudostratified columnar 9-Pseudostratified columnar epitheliumepithelium

• It appears to be stratified but it is composed of single layer of cells that all are resting on the basal lamina but only some of cells reach the surface of epithelium. Theses tall cells have narrow base and broad apical surface. Cells not extending to the surface have broad base and narrow apical end. The nuclei are located at different levels .Ciliated Pseudostratified epithelium has ciliated tall cells that reach the free border (ex. trachea, primary bronchi, and nasal cavity

Pseudo stratified columnar ciliated epithelium with goblet cells.

Glands

• 1-Exocrine glands: secrete their products via ducts

• 2-Endocrine glands: are ductless, their products pass into the blood or lymph.

* Each gland if formed of stroma (C.T. that support and invade the parenchyma ie.capsule and septa) and parenchyma (secretory units and ducts).

Types of Exocrine Glands(shape)

Goblet cell

Endocrine glands• They secrete hormones that pass directly into

the blood or lymph with ducts.

• Their cells are arranged either in cords as in pituitary gland or as follicles as in thyroid glands.

• Diffuse neuroendocrine system, are widespread throughout the digestive tract and respiratory system.

Pituitary Gland

Thyroid Gland