Animal Tissues

The animal tissues are of following types:

1. Epithelial Tissue— They are further classified as follows:
   1. Squamous epithelium — It protects the body and the organs from injury and entry of germs.
   2. Columnar epithelium — They are present in the linings of the stomach, intestines and pharynx. They are specialized to absorb nutrients.
   3. Cuboidal epithelium — They are found in thyroid gland, kidney tubules, salivary gland, pancreas and liver. They are specialized to secrete enzymes and hormones and remove waste (as in kidneys).
2. Muscular tissue— They are of following types:
   1. Voluntary muscles — These muscles help in the movement of the bones.
   2. Involuntary muscles — These muscles are not under our control or will. They help in movement of food, movement of urine from urinary bladder and so on.
   3. Cardiac muscles — Cardiac muscles cause the rhythmic movement of the heart resulting in circulation of blood in the body.
3. Nervous tissues— Nervous tissues help in the control and coordination of the body. The information or message is transmitted by a neuron in the form of impulses and in one direction only.
4. Connective tissue— They are further classified into following types:
   1. Connective tissue proper — This tissue connects various parts of the body. It connects muscles to bones, bones to other bones and gives support by filling up spaces between the organs.
   2. Skeletal tissue — It is solid connective tissue which provide support to the body. It constitutes of bone and cartilage.
   3. Fluid connective tissue — It is the liquid connective tissue consisting of blood and lymph. It has functions like transportation of oxygen and nutrients and fighting infection.

On the basis of shape of the cells, epithelial tissues are classified into three types :

1. Squamous epithelium — The cells of squamous epithelium are flat, hexagonal or irregular in shape. These cells line the inner walls of the blood vessels, lungs, heart and oesophagus. They also form the epidermis of the skin, where they provide protection and prevent the entry of germs.
   Below diagram shows the structure of Squamous epithelium:

2. Columnar epithelium — The length of the cells of Columnar epithelium appears much more than their width. The cells are placed side by sides like columns. The nucleus is present towards the base of the cell. They are present in the linings of the stomach, intestines and pharynx. They are specialized to absorb nutrients.
   Below diagram shows the structure of Columnar epithelium:

3. Cuboidal epithelium — The cells of Cuboidal epithelium have almost equal height and width. The nucleus is centrally located. They are found in thyroid gland, kidney tubules, salivary gland, pancreas and liver. They are specialized to secrete enzymes and hormones and remove waste (as in kidneys).
   Below diagram shows the structure of Cuboidal epithelium:

Based on the structure and functions performed muscular tissues are of three types — Voluntary muscles, Involuntary muscles and Cardiac muscles.

1. Voluntary muscles — These muscles are under our control or will. For example, we can control the muscles in our arms and legs when we run, walk or jump. These muscles are also called skeletal muscles as they are attached to the bones. These muscles help in the movement of the bones. The cells of these muscles are long and cylindrical with many nuclei and dark and light bands called striations. Hence, they are also called striated muscles.
2. Involuntary muscles — They are present in the internal organs of our body like stomach, intestine, bladder etc. They are not under our control. The cells of these muscles are spindle-shaped and have only one nucleus. They do not have any bands or striations, hence these are also called unstriated muscles.
3. Cardiac muscles — The heart is made up of special type of involuntary muscles called cardiac muscles. Cardiac muscles works continuously without getting tired. Structurally, these muscles resemble voluntary muscles . However, cardiac muscles are similar to involuntary muscles in their function.

The connective tissue consists of cells with spaces between them. These spaces are filled with a matrix or ground substance. The living cells produce the non-living matrix, which could be a liquid (in blood), semi-solid (connective tissue proper) or solid (bone). The connective tissues join different parts of the body and provide support to them. They also fill up the space between various organs. They are further classified into following types:

1. Connective tissue proper — This tissue connects various parts of the body. It connects muscles to bones, bones to other bones and gives support by filling up spaces between the organs.
2. Skeletal tissue — It is solid connective tissue which provide support to the body. It constitutes of bone and cartilage.
3. Fluid connective tissue — It is the liquid connective tissue consisting of blood and lymph. It has functions like transportation of oxygen and nutrients and fighting infection.

The connective tissue is different from other tissues because it has cells that are separated from each other. The space between the cells is composed of different intercellular substances that form the matrix or ground substance.

Two functions of epithelial tissues:

1. They provide protection and prevent the entry of germs.
2. They are specialized to secrete enzymes as in salivary gland.

Neuron has a central part called the cell body or cyton. Many thread-like branches extend from the cyton. These thread-like branches extending from all sides of the cell body are called dendrons. Dendrons further divide to form dendrites. One of these extensions is longer than the rest and is called the axon. Functions of neuron:

1. Neuron help in the control and coordination of the body.
2. The information or message is transmitted by a neuron in the form of impulses and in one direction only.
3. Many neurons or nerve fibres bound together constitute a nerve.

Squamous epithelium lines the blood vessels and forms the epidermis of the skin.

Cuboidal epithelium is found in the thyroid gland.

Voluntary muscles are also called striated muscles.

Involuntary muscles cells have only one nucleus and have no striations.

Cardiac muscles work continuously and do not get tired.

The correctly labelled nerve cell is shown below:

Voluntary muscles — The muscles that are under our control and help in the movement of the bones are called voluntary muscles. For Example - muscles of hands and legs.

Cardiac muscles — The special type of involuntary muscles, present in heart, that work continuously without getting tired are called cardiac muscles.

Connective tissue — Connective tissues join different parts of the body and provide support to them. They also fill up the space between various organs.

Connective tissue proper — Connective tissue proper connects various parts of the body, like muscles to bones or bones to other bones and gives support by filling up spaces between the organs.

Adipose tissue — The type of connective tissue which is primarily located beneath the skin, and is also found around the internal organs, providing cushion and insulation to the body is called adipose tissue.

Cartilage — The highly elastic skeletal tissue that consists of a ground substance called matrix with cells is called Cartilage.

Epithelial tissue consists of cells without any intercellular spaces.

Skeletal muscles help in the movement of the limbs.

The neurons or nerve fibres constitute the nerves.

A ligament connects one bone to another.

Adipose tissue cushions and insulates the body.

Lymph is a fluid connective tissue without red blood cells.

lymph

Reason — Lymph is a fluid connective tissue while others are connective tissue proper.

Squamous epithelium

Reason — Squamous epithelium is epithelial tissue while others are connective tissue.

epithelium

Reason — Thrombocytes, erythrocytes and leucocytes are components of blood whereas epithelium is epithelial tissue.

Red Blood Cells

White Blood Cells

Blood Platelets

The labelled diagrams are shown below:

1. Columnar epithelium tissue
2. Cardiac Muscles
3. Adipose tissue

cylindrical and unbranched

Reason — Voluntary muscles are cylindrical and unbranched.

dendrons

Reason — The short thread-like branches arising from the cell body of a nerve cell are called dendrons, which further divide to form dendrites.

muscles to a bone

Reason — The tendons join the muscles to the bones.

matrix

Reason — The cartilage cells are found dispersed in the the ground substance called matrix.

RBCs

Reason — RBCs are the most abundant component of the blood.

False

Corrected statement — Involuntary muscles are present in the internal organs of the body.

True

True

True

True