General Histology

EpitheliumBlood

Fertilization: formation of zygote

Cleavage: becoming multicellular

Gastrulation: fomation of 3 primary tissues – ectoderm, endoderm, mesoderm

Tissues of adult organismA tissue is defined as a group of similar cells with their

extracellular products, specialized in common direction and set apart for the performance of a common function

About 200 types of specialized cells in adult human body are arranged into 4 main tissues:

• Epithelium

• Blood and connective tissues

• Muscular tissues

• Nervous tissues

Tissue formation is called Histogenesis

Tissues are studied in General Histology course

Epithelium

Epithelium hallmarks• Epithelium covers body surfaces, lines body

cavities, and constistutes glands, therefore it is subdivided into lining and glandular

• Epithelium creates a selective barrier between the external environment and the underlying connective tissue

• The cells predominate, they are closely apposed and adhere to one another by means of special junctions

• Their basal surface is attached to an underlying basement membrane

• Apical surface may contain nicrovilli and cilia

Classification of lining epithelia

Location of different types epithelium

SIMPLE Lining of vascular system

SQUAMOUS Lining of body cavities

Bowman`s capsule

Lining of lung alveoli

SIMPLE Small ducts of exocrine CUBOIDAL glands

Surface of ovary

Kidney tudules

Location of different types epithelium

SIMPLE Lining of small intestine

COLUMNAR: and colon

Stomach and gastric glands

Lining of gallbladder

PSEUDO- Lining of trahea and bronchi

STRATIFIED Lining of ductus deferens

Efferent ductules of epididymis

Location of different types epithelium

STRATIFIED Epidermis

SQAMOUS: Lining of oral cavity and esophagus

Lining of vagina

STRATIFIED Sweat glands, ducts

CUBOIDAL: Lager ducts of exocrine glands

Anorectal junction

Location of different types epithelium

STRATIFIED Largest ducts of exocrine

COLUMNAR: glands

Anorectal junction

TRANSITIONAL: Renal calyces

Ureters

Urinary bladder

Urethra

Specialized surfaces of epitheliocytes

• Apical specializations:

- microvilli and cilia• Lateral specializations:

- zonulae occludentes

- zonulae adherentes

- maculae adherentes

- gap junctions

• Basal specializations:

- hemidesmosomes

- basal striations

Microvilli and terminal web

Structure of a cilium

Electron micrographs of cilia

Lateral specializations of epitheliocytes

Classification of glands

Multicellular exocrine glands classifiication

Modes of secretion: A – holocrine; B – merocrine; C - apocrine