Zoology lecture notes and study materials

Epithelial Tissue: (Types, Structure, Functions & Examples)


classification of epithelial cells

Classification of Epithelial Tissue in Animals

Epithelial Tissue: (Structure, Classification and Functions)
(Structure Classification and Functions of Simple and Compound Epithelium)

What is Epithelium?

Ø  Epithelium is a tissue system in animals.

Ø  Epithelium constitutes the outer layer of body surfaces, linings of the alimentary canal and the walls of hollow structures.

Ø  It covers the internal or external surfaces of the body.

Ø  Epithelial cells are held together by carbohydrate based cementing materials.

Ø  They also possess special junctions between the cells.

Ø  The bottom layer of epithelium is rest on the basement membrane.

Ø  The basement membrane composed of a network of fibrous proteins particularly rich in collagens.

Ø  Epithelial layers are NOT provided with any blood vessels.

Ø  The cells of the epithelium obtain nutrients and oxygen by diffusion from the lymphatic vessels.

Ø  Nerve endings occur in the epithelial tissues for receiving stimuli.

What are the Functions of Epithelial Tissue?

Ø  Epithelium provides protection to the underlying structures.

Ø  Protect organs from injuries by external agencies or pressure.

Ø  Prevent infection by microorganisms.

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Human Physiology Lecture Notes

Artery vs Vein: Similarities and Differences (A Comparison Table)


difference between artery and vein

Arteries vs Veins
Similarities and Differences between Arteries and Veins

The circulatory system in an organism ensures the transport of oxygen, nutrients, carbon dioxide and hormone throughout the body. The blood circulatory system in an animal is facilitated by the heart (the blood pumping organ) and blood vessels (closed pipelines which carry out the circulation of blood throughout the body). There are three types of blood vessels in our body. They are:

(1).    Arteries
(2).    Veins
(3).    Capillaries

(1). Artery: They are blood vessels which originated from the heart and carry blood away from the heart. Arteries usually carry oxygenated blood except for pulmonary and umbilical arteries that carries deoxygenated blood.

(2). Vein: They are blood vessels which carry blood to the heart from various organs of the body. Veins usually carry deoxygenated blood except for pulmonary and umbilical vein that carries oxygenated blood.

(3). Capillaries: They are minutes blood vessels of one cell layer thickness and they facilitate the exchange of oxygen, carbon dioxide, nutrients and hormones in the blood to individuals cells of different organs. Arteries and veins are interconnected through capillaries and thus the blood circulation forms a closed system in majority of animals.

The current post describes the similarities and differences between Arteries and Veins with a comparison table.

Similarities between Arteries and Veins

Ø  Both are blood vessels.

Ø  Both transport blood.

Ø  Blood transport is unidirectional in both arteries and vein.

Ø  Arteries and veins composed of layers of cells.

Ø  Both arteries and veins composed of three layers of cells namely Tunica externa (external layer), tunica media (middle layer) and tunica interna (internal layer).

Ø  Both arteries and veins are covered by muscular tissues which assist in the contraction or expansion of blood vessels.

Ø  Both undergo vasoconstriction and vasodilation to adjust the blood pressure according to the action of hormones and neurotransmitters.

Ø  Both arteries and veins show anastomosis.

Difference between Arteries and Veins

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Zoology lecture notes and study materials

Phylum Arthropoda : General Characters


what are the general characters of phylum arthropoda

Arthropoda is a largest Phylum of Kingdom Animalia, includes about 80% of all known animal species in the biosphere including terrestrial and aquatic biomes. The phylum includes insects, crustaceous, centipedes, millipedes, spiders etc. The word Arthropoda is derived from two Greek words, ‘arthro’ = joint and ‘podo’ = foot. Phylum Arthropoda is characterized by:

@. Segmented body plan

@. Paired jointed appendages

@. Chitinaceous exoskeleton

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General characters of Phylum Arthropoda:

@. Cosmopolitan distribution

@. Presence of exoskeleton, made of chitin

@. Chitin= a structural homo-polysaccharide of N-acetylglucosamine linked by β-1, 4 glycosidic bond

@. Segmented appearance of body

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