Animal tissues-Living tissues - science lessons for life


Tuesday, November 29, 2016

Animal tissues-Living tissues

Animal tissues
The animal body is also made up of different types of cells.
Example :- The human body is made up of about 210 different types of cells.
There are groups of cells with common origin to perform a specific function in the multicellular animal body. Main types of animal tissues are given below.

  • Epithelial tissue
  • Connective tissue
  • Muscle tissue
  • Nervous tissue
Epithelial tissue
This is the tissue that lines up the free surfaces (internal and external) of the vertebrate body. Some of them are composed of single layer of cells and the others are with several cell layers.

Features of epithelial tissues

  • The cells are placed on a basement membrane
  • The cells are tightly packed
  • A nerve supply is present within the tissue but there is no blood supply
The epithelial tissue is classified according to the shape of the cell and the number of cell layers.
Examples for several locations of epithelial tissues are given below.

  • Wall of blood capillaries
  • Thyroid gland
  • Lining of nasal cavity
  • Wall of urinary bladder
  • Skin (Epidermis)
Functions of epithelial tissue
  • Lining up of free surfaces and protection - Protects the internal organs from pressure, friction and microbes
  • Absorptive function - The epithelium of digestive tract absorbs digestive end products
  • Perception of stimuli - The epithelium of tongue and nose, detect taste and smell senses
  • Secretory function - Secretion of mucous by the lining epithelium of respiratory tract
  • Filtering - Epithelium of Bowman's capsule in nephrons, filters blood
Connective tissue
Connective tissue is composed of different types of cells and fibres. These cells and fibres are embedded in a large matrix.
Most connective tissues
possess nerve and blood supply.

The connective tissues provide connection between tissues and organs and provide support too.
E.g. :- Blood tissue, Bone tissue

Blood tissue
Blood is a special connective tissue The speciality is that the matrix (plasma) is not secreted by the blood cells. Blood tissue helps in maintaining proper connection between organs and tissue of the human body.

Features of blood tissue
  • Blood is composed of a fluid matrix called plasma and cells
  • The matrix contains cells called red blood cells (erythrocytes) and white blood cells (leucocytes) and cellular fragments called platelets
  • Fibres are not found always but during blood clotting they appear

Functions of blood tissue
  • Transportation of materials - Nutrients, respiratory gases, excretory materials and hormones are transported to the relevant organs
  • Protection - White blood cells destroy foreign bodies (Microbes) by phagocytosis and by producing antibodies
  • Maintenace of homeostasis
Muscle tissue
Muscle tissue is one of the main tissues that makes up the human body. Muscletissue is made up of muscle cells or muscle fibres. These muscle fibres possess contraction and relaxation ability. Not like epithelium, the muscle tissue possesses a good blood supply. Therefore muscle tissue receives oxygen and nutrients at a high rate. Muscle tissue acts as one of the effectors in responding in coordination.

Muscle tissue is of three types,
  • Smooth muscle tissue
  • Skeletal muscle tissue
  • Cardiac muscle tissue
Smooth muscle tissue
Smooth muscle tissue is made up of smooth muscle cells. This tissue is found in the walls of organs with cavities.
Example :- Walls of digestive tract, uterus, blood vessels and bladder

Features of smooth muscle cell
smooth muscle cell

  • These cells are spindle shaped and present separately. The cells are unbranched
  • These cells have one nucleus at the centre. No striations
  • These cells do not become fatigue quickly. They are controlled involuntarily
Skeletal muscle tissue
Skeletal muscle tissue is made up of skeletal muscle fibres. These are mostly associated with skeletal system. The skeletal muscles help in locomotion and movements of chordates.

Features of skeletal muscle fibres
Skeletal muscular tissue

  • Skeletal muscle fibres are long, cylindrical, unbranched cells.
  • They are multinucleate cells with striations. The nuclei present peripherally, and many mitochondria are present in them.
  • These cells are voluntarily controlled and become fatigue easily.
E.g. :- Bicep muscle, Tricep muscle, Muscles in leg, Facial muscles

Cardiac muscle tissue
Cardiac muscle tissue is made up of cardiac muscle cells. It is exclusively found in the vertebrate heart.

Features of cardiac muscle fibres
Cardiac muscle tissue
  • Cardiac muscle cells are uninucleate, striated and short cells
  • Intercalated discs are present among cells
  • They never become fatigue. They contract rhythmically
  • They are involuntarily controlled
Nervous tissue
Stucture of a typical neuron

It is an important tissue found in chordates body. The stuctural unit of nervous tissue is nerve cell or neuron. Neurons are specialised to transmit impulses.

Features of neuron
  • Neuron is composed of two parts. They are cell body and nerve fibres
  • Nucleus, mitochondria, golgi body and endoplasmic reticulum are found in the cell body
  • Axon arises from the cell body as a single process. The axon transmits impulses away from the cell body.
  • Dendrons branch out to form dendrites. Dendrites receive stimuli and transmit impulses to the cell body

Most of the axons in chordates are myelinated. Myelin sheath is not continuous and the interrupted places are known as nodes of Ranvier. The myelin sheath increases the speed of transmission.

Functions of neurons
The function of the neuron is to receive the information from the receptors (eye, ear, nose tongue, skin) or another neuron and to transmit them to the effector (muscles) or to another neuron.
According to the function of the neuron, they can be divided into three types as follows,

  • Sensory neuron
  • Inter neuron
  • Motor neuron
Types of neurons

source by internet and books

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