Comparative anatomy Is a branch of zoology deals
ﻋﻠﻢ ﺍﻟﺘﺸﺮﻳﺢ ﺍﻟﻤﻘﺎﺭﻥ Comparative anatomy • Is a branch of zoology deals with studying the relationships of the structure and origin of all organ systems of all forms in the animal kingdom.
Integumentary and exoskeletal system • The dermal system consist of skin and its derivatives such as: scales, feathers, claws, nails, horns and hoofs, the skin glands such as: mucous, sweat an poisonous glands. • The integument covered all the surface of the body. • The skin has many important functions: • Protection, respiration, regulation, locomotion
• The glands: are developed from epidermis and extend into the dermis, there are two types: • A) simple unicellular glands: where one cell of the cells of stratum mucosum becomes specialized and secretory in function such as mucous and goblet cells
B) Compound “multicellular” glands where the cells of stratum germinativum invaginate into the dermis and form saccular structure which opens on the surface of skin through the neck of the gland: - tubular type such as sweat and mammary glands - Alveolar type such as sebaceous and poisonous glands - Poisonous glands found at the base of the pectoral spines or on the dorsal spines of some teleosts
The exoskeletal derivatives 1. The epidermal exoskeleton: - is produced as a result of the activity of the malpighian layer. • It consist of flat horny cells which condence togeether forming a hard structures such as: - horny teeth of cyclostomes - horny scales of reptiles - feathers of birds - hairs of mammals - claws of some amphibians, reptiles, birds and some mammals - nails of human - horns and hoofs of mammals
2. The dermal exoskeletal derivatives: it is produced by the mesenchemal cells which originate from the mesoderm such as : - bony scales of bony fishes - fin rays and fin spines of fishes. 3. The derivatives from both epidermis and dermis: - Placoid scales of cartilagenous fishes - True teeth of mammals
The dermal system of Amphioxus • The skin is consist of two layers: • Epidermis: is a single layer of columnar epithelium cells , there are glandular unicellular cells called goblet cells secret mucous substance protect the body surface • It covered with cuticle.
• The dermis: is mesodermal in origin very thin consists of connective tissue that contains blood capillaries and nerve endings • Below the dermis there is a compact layer with few fibres called subcutaneous layer that surrounded the muscles of the body wall(myotomes).
The dermal system of petromyzon • The epidermis: is stratified epithelium, consisted of an active layer (stratum germinativum) and flattened cells above covered with cuticle. Numerous mucous secretory (large in size, mononucleated and containing several granules) and sensory cells (binucleated or cub – shaped cells) are distributed in the epidermis.
• The dermis: is much thickness, consists of fibrous connective tissue, blood capillaries and nerve endings. • Pigment cells are present in both epidermis and dermis just below the epidermal layer • The skin is smooth, there is no exoskeletal derivatives.
Horney teeth
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