Animal Physiology

In my Biology class ,  we learned about the Animal Physiology. One of the interesting part was a bout

the four major tissue types in animals: Epithelial tissues, Connective tissue, Muscle tissues,and Nervous tissue.

 

Epithelial tissues or Epithelia are called sheets of cells which cover the outside of the body and line organs and cavities within the body. Epithelial cells work as a wall against mechanical injury, pathogens, and fluid loss because they are closely packed with tight junctions. Also, Epithelia cells form active interfaces with the environment. For example, Stratified squamous epithelium that exist the nasal passages is essential for olfaction, the sense of smell.

Connective tissue, is made up of a sparse population of cells scattered through an extracellular matrix, holds many tissues and organs together and in place. Connective tissue mostly contains of a web of fibers embedded in a liquid, jellylike, or solid foundation. Contained by the matrix are numerous cells called fibroblasts, which secrete fiber proteins, and macrophages, which engulf foreign particles and any cell debris by phagocytosis.

Three different kinds of Connective tissue fibers are Collagenous fibers are responsible for strength and flexibility, reticular fibers join connective tissue to neighboring tissues, and elastic fibers make tissues elastic.

Muscle tissues provide nearly all types of body movement. All muscle cells contain of filaments containing the proteins actin and myosin, which together allow muscles to contract. There are three types of muscle tissue in the vertebrate body: skeletal, smooth, and cardiac.

Nervous tissue functions in the receiving, processing, and transmission of information. Nervous tissue is composed of nerve cells and glial cells. Nerve cells transfer nerve impulses and glial cells function as support. In most of animals, a brain is an information-processing center which is formed of concentration of nervous tissue.

   

An other i interesting subject which was discussed was about the relationship between body size and metabolic rate per unit body mass in endotherms.The relationship between body size and metabolic rate is inverse. It means that small animals have higher metabolic rate because of the ratio between their body surface and volume is a great number (almost one.) Small animals eat more food compared to their body size. Because of their high metabolic rate, they burn relatively more calories than a larger endotherm. The ratio between their body surfaces and volumes in large animals is a small number. The amount of food that they eat is small amount relative to their body size. Therefore, their metabolic rate is low.