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Areolar tissue is a loose connective tissue found under the skin, between muscles, bones, around organs, blood vessels and peritoneum. It is composed of fibres and cells. 

The matrix of areolar tissues contains two types of fibres i.e. white fibres and yellow fibres. 

a. White fibres: They are made up of collagen and give tensile strength to the tissue. 

b. Yellow fibres: They are made up of elastin and are elastic in nature. The four different types of cells present in this tissue are as follows: 

a. Fibroblast: Large flat cells having branching processes. They produce fibres as well as polysaccharides that form the ground substance or matrix of the tissue. 

b. Mast cells: Oval cells that secrete heparin and histamine.

c. Macrophages: Amoeboid, phagocytic cells. 

d. Adipocytes (Fat cells): These cells store fat and have eccentric nucleus.

A neuron is the structural and functional unit of the nervous tissue. A neuron is made up of cyton or cell body and cytoplasmic extensions or processes. 

1. Cyton: The cyton or cell body contains granular cytoplasm called neuroplasm and a centrally placed nucleus. The neuroplasm contains mitochondria, Golgi apparatus, RER and Nissl’s granules.

2. Cytoplasmic extensions or processes: The fine branches of a dendron are called dendrites. Dendrites carry an impulse towards the cyton. 

a. Dendron: They are short, unbranched processes.

b. Axon: It is a single, elongated and cylindrical process. The axon is bound by the axolemma. The protoplasm or axoplasm contains large number of mitochondria and neurofibrils. 

The axon is enclosed in a fatty sheath called the myelin sheath and the outer covering of the myelin sheath is the neurilemma. Both the myelin sheath and the neurilemma are parts of the Schwann cell. The myelin sheath is absent at intervals along the axon at the Node of Ranvier. 

The fine branching structure at the end of the axon (terminal arborization) is called telodendron. 

1. Nissl’s Granules 

2. Nissl’s granules are large granular bodies, found in neurons. These granules are made up of rough endoplasmic reticulum (RER) and free ribosomes (site of protein synthesis). 

3. It was named after Franz Nissl, a German neuropathologist who invented the Nissl staining method.

A neuron is the structural and functional unit of the nervous tissue. A neuron is made up of cyton or cell body and cytoplasmic extensions or processes. 

1. Cyton: The cyton or cell body contains granular cytoplasm called neuroplasm and a centrally placed nucleus. The neuroplasm contains mitochondria, Golgi apparatus, RER and Nissl’s granules. 

2. Cytoplasmic extensions or processes: 

(a) Dendron: They are short, unbranched processes. The fine branches of a dendron are called dendrites. Dendrites carry an impulse towards the cyton.

(b) Axon: It is a single, elongated and cylindrical process. 

1. The axon is bound by the axolemma. 

2. The protoplasm or axoplasm contains large number of mitochondria and neurofibrils. 

3. The axon is enclosed in a fatty sheath called the myelin sheath and the outer covering of the myelin sheath is the neurilemma. Both the myelin sheath and the neurilemma are parts of the Schwann cell. 

4. The myelin sheath is absent at intervals along the axon at the Node of Ranvier. 

5. The fine branching structure at the end of the axon (terminal arborization) is called telodendron.

Columnar Epithelium: 

Location: It is found in inner lining of intestine, gall bladder, gastric glands, intestinal glands, etc. 

Structure: 

1. The cells are tall, pillar-like. The inner ends of the cells are narrow while free ends are broad and flat. 

2. Nucleus is oval or elliptical in the lower half of the cell. 

3. Free surface shows large number of microvilli. 

Function: Secretion and absorption.

1. Epithelial tissue (Columnar epithelium) 

2. Cardiac muscles (Muscular tissue)

3. Epithelial tissue (Stratified epithelium) 

4. Nervous tissue 

5. Epithelial tissue (Ciliated epithelium)

1. In adipose tissues, fats are stored in the form of droplets. 

2. The adipose tissue acts as good insulator and helps retain heat in the body. This helps in survival of animals in the colder regions. Hence, animals in cold regions have a layer of fat below their skin.

Basement membrane is a non – cellular membrane on which the lowermost layer of the epithelium lies.

The cells of the germinal epithelium divide meiotically to produce haploid gametes, e.g. Lining of seminiferous tubules, inner lining of ovary, etc.

1. Cuboidal Epithelium: 

Location: It is present in the lining of pancreatic ducts, salivary duct, proximal and distal convoluted tubules of nephron, etc.

Structure: 

1. The cells are cuboidal in shape. 

2. They have a centrally placed, spherical nucleus. Functions: Absorption and secretion. 

2. Structure: 

1. The cells of the glandular epithelium can be columnar, cuboidal or pyramidal in shape. 

2. The nucleus of these cells is large and situated towards the base. 

3. Secretory granules are present in the cell cytoplasm. 

4. Glands consist of glandular epithelium. The glands may be either unicellular (goblet cells of intestine) or multicellular (salivary gland), depending on the number of cells. 

5. Types: Depending on the mode of secretion, multicellular glands can be further classified as duct bearing glands (exocrine glands) ad ductless glands (endocrine glands).

a. Exocrine glands: These glands pour their secretions at a specific site. e.g. salivary gland, sweat gland, etc. 

b. Endocrine glands: These glands release their secretions directly into the blood stream, e.g. thyroid gland, pituitary gland, etc. 

6. Function: Glandular epithelium secretes mucus to trap the dust particles, lubricate the inner surface of respiratory and digestive tracts, secrete enzymes and hormones, etc. 

Heterocrine glands: 

1. Heterocrine glands or composite glands have both exocrine and endocrine function. 

2. Pancreas is called a heterocrine gland because it secretes the hormone insulin into blood which is an endocrine function and enzymes into digestive tract which is an exocrine function.

1. Sensory epithelium 

2. Glandular epithelium

3. Columnar epithelium 

4. Ciliated epithelium 

5. Transitional epithelium (Compound epithelium)

Sensory epithelium is composed of a modified form of columnar cells and elongated neurosensory cells. Sensory hairs are present at the free end of these cells. 

Function: It perceives external as well as internal stimuli. 

Location: It is found in the nose (Olfactory), ear (Auditory hair cells) and eye (photoreceptors).

In a multicellular organism, cells are broadly classified into two types:

 i. Somatic cells 

ii. Germ cells 

1. Somatic cells: All body cells except the sperm and the ova are called as somatic cells. 

2. Germ cells: The sperm and the ova are known as germ cells. They are related to reproductive system.

1. Various tissues combine together in an orderly manner to form large functional units called organs, e.g. Kidneys.

2. Number of organs combine together to form an organ-system, e.g. Respiratory system.

Multicellular organisms are those composed by multiple cells. They are classified in 13 major groups of terrestrial living beings, including animals, plants, fungi, ciliates, algae, and foraminifera.The cells in a multicellular organism are usually varied, differentiated, and specialized.

Cells → Tissues → Organs → Organ Systems → Body

The study of structure and arrangement of tissue is called histology.

The study of structure and arrangement of tissue is called histology.

There are four types of animal tissues namely, epithelial, connective, muscular and nervous tissue.

Hyaline cartilage: The hyaline cartilage is elastic and compressible in nature. 

a. Perichondrium is present in this cartilage. 

b. Its matrix is bluish white and gel like. 

c. Very fine collage fibres and chondrocytes are present in this cartilage. 

Function: It acts as a good shock absorber as well as provides flexibility. It reduces friction. 

Location: It is found at the end of long bones, epiglottis, trachea, ribs, larynx and hyoid.

Types: Depending on the mode of secretion, multicellular glands can be further classified as duct bearing glands (exocrine glands) ad ductless glands (endocrine glands). 

a. Exocrine glands: These glands pour their secretions at a specific site. e.g. salivary gland, sweat gland, etc. 

b. Endocrine glands: These glands release their secretions directly into the blood stream, e.g. thyroid gland, pituitary gland, etc.

Cartilage is a type of supporting connective tissue. It is a pliable yet tough tissue. 

Structure: 

1. Abundant matrix is delimited by a sheath of collagenous fibres called perichondrium. 

2. The matrix is called chondrin. 

3. Below the perichondrium, immature cartilage forming cells called chondroblasts are present.

4. Chondroblasts mature and get converted into chondrocytes.

1. Tendons are a type of dense regular connective tissue. 

2. Tendons connect skeletal muscles to bones. 

3. They contain bundles of white fibres which give tensile strength to the tissue, e.g. Achilles tendon, Hamstring tendon.

Structure:

1. They consist of large number of fasciculi which are wrapped by a connective tissue sheath called epimysium or fascia. Each individual fasciculus covered by perimysium. 

2. Each fasciculus in turn consists of many muscle fibres called myofibers. 

3. Each muscle fibre is a syncytial fibre that contains several nuclei. 

4. The sarcoplasm (cytoplasm) is surrounded by the sarcolemma (cell membrane). 

5. The sarcoplasm contains large number of parallelly arranged myofibrils and hence the nuclei gets shifted to the periphery. 

6. Each myofibril is made up of repeated functional units called sarcomeres. 

7. Each sarcomere has a dark band called anisotropic of ‘A’ band in the centre. ‘A’ bands are made up of the contractile proteins actin and myosin.

8. In the centre of the ‘A’ band is the light area called ‘H’ zone or Hensen’s zone. 

9. In the centre of the Hensen’s zone is the ‘M’ line. 

10. On either side of the ‘A’ band are light bands called isotropic or ‘I’ bands. These bands contain only actin. Adjacent light bands are separated by the ‘Z’ line (Zwischenscheibe line). 

11. The dark and light bands on neighbouring myofibrils correspond with each other to give the muscles a striated appearance. 

Functions: Skeletal muscles bring about voluntary movements of the body

Neurons are classified into three types based on their functions: 

1. Afferent neuron (Sensory neuron): 

Function: It carries impulses from sense organ to the central nervous system (CNS). 

Location: It is found in the dorsal root of the spinal cord. 

2. Efferent Neuron (Motor neuron): 

Function: It carries impulses from CNS to effector organs. 

Location: It is found in the ventral root of the spinal cord. 

3. Interneuron or association neuron: 

Function: They perfonn processing, integration of sensory impulses and activate appropriate motor neuron to generate motor impulse.

Location: These are located between sensory and motor neurons.

1. cartilage 

2. skeletal tissue 

3. loose

Fibroblasts are the cells of connective tissue which form fibres.

1. Blood and lymph are fluid connective tissues present in the body of animals. 

2. It is classified into two types i.e., cartilage and bone.

Characteristics: 

1. It consists of a variety of cells and fibres which are embedded in the abundant intercellular substance called matrix. 

2. It is a highly vascular tissue, except cartilage. 

3. The connective tissue is classified on the basis of matrix present, into three types, namely connective tissue proper, supporting connective tissue and fluid connective tissue. 

a. Connective tissue proper is further classified as loose connective tissue (e.g. areolar connective tissue and adipose tissue) and dense connective tissue (e.g. ligament and tendon). 

b. Supporting connective tissue also called skeletal tissue includes cartilage and bone. 

c. Fluid connective tissue includes blood and lymph.

The correct answer is (A) white

1. The cells of the muscular tissue are elongated and are called as muscle fibres. 

2. The muscle fibres are covered by a membrane called sarcolemma. 

3. The cytoplasm of the muscle cell is called the sarcoplasm. 

4. Large number of contractile fibrils called myofibrils are present in the sarcoplasm. 

5. Depending on the type of muscle cells, one or many nuclei may be present.

6. Myofibrils are made up of the proteins, actin and myosin. 

7. Muscle fibres contract and decrease in length on stimulation. Hence, muscular tissue is also known as contractile tissue. 

8. This tissue is vascular and innervated by nerves. 

9. Muscle cells contain large number of mitochondria.

1. Epithelial tissue – Protection, secretion, absorption, excretion and filtration. 

2. Connective tissue – Provides strength to body tissues and organs, protects vital organs, acts as packing material, helps in healing 

3. Muscular tissue – Movement of body parts and locomotion. 

4. Nervous tissue – Control and coordination by nerve impulse.

Blood and lymph are fluid connective tissues present in the body of animals.