Structural Organisation in Animals – Class 11 Biology Notes
Introduction to Structural Organisation in Animals
The structural organization in animals refers to how cells, tissues, organs, and organ systems are arranged to perform specific functions. Animals have a higher degree of complexity than plants, and their structures are specialized to carry out various physiological functions required for survival. In this chapter, we will focus on the different types of animal tissues, organ systems, and their functions.
1. Animal Tissues
Animal tissues are classified into four main types based on their structure and function:
- Epithelial Tissue
- Connective Tissue
- Muscle Tissue
- Nervous Tissue
1.1. Epithelial Tissue
Epithelial tissue covers and lines the surfaces of the body, organs, and cavities. It serves as a protective barrier, regulates absorption and secretion, and plays a role in sensation.
Types of Epithelial Tissue:
- Squamous Epithelium: Flat cells, found in areas where passive diffusion occurs, such as the lining of blood vessels and alveoli in the lungs.
- Cuboidal Epithelium: Cube-shaped cells, found in glands and ducts, involved in secretion and absorption.
- Columnar Epithelium: Tall, column-shaped cells, found in the lining of the intestines, responsible for absorption and secretion.
- Ciliated Epithelium: Columnar or cuboidal cells with hair-like projections (cilia), found in the respiratory tract and fallopian tubes, responsible for moving particles or fluids.
- Stratified Epithelium: Multiple layers of cells, found in areas subjected to wear and tear, such as the skin.
1.2. Connective Tissue
Connective tissue provides support, binds, and connects other tissues. It also stores nutrients and helps in transporting substances.
Types of Connective Tissue:
- Loose Connective Tissue: Soft and flexible, found beneath the skin and around organs.
- Example: Areolar tissue, adipose tissue (fat).
- Dense Connective Tissue: Tightly packed fibers, found in tendons and ligaments.
- Cartilage: Flexible, semi-rigid tissue found in joints, ears, and nose.
- Bone: Hard connective tissue, forms the skeleton and provides structure.
- Blood: Liquid connective tissue, responsible for transport of nutrients, gases, and waste products.
1.3. Muscle Tissue
Muscle tissue is responsible for movement and consists of cells that can contract and relax.
Types of Muscle Tissue:
- Skeletal Muscle: Striated, voluntary muscle attached to bones for movement. It has a striped appearance.
- Cardiac Muscle: Striated, involuntary muscle found in the heart. It contracts rhythmically to pump blood.
- Smooth Muscle: Non-striated, involuntary muscle found in the walls of hollow organs such as the intestines, bladder, and blood vessels.
1.4. Nervous Tissue
Nervous tissue is involved in receiving stimuli and transmitting impulses throughout the body. It is composed of neurons (nerve cells) and supporting cells (neuroglia).
Structure of a Neuron:
- Cell Body (Soma): Contains the nucleus and other organelles.
- Dendrites: Receive impulses from other neurons or receptors.
- Axon: Transmits impulses to other neurons or effectors.
- Synapse: Junction between two neurons where neurotransmitters facilitate communication.
2. Organ Systems in Animals
In animals, the tissues are organized into organs, and the organs work together to form organ systems, each performing specific physiological functions.
2.1. Digestive System
The digestive system is responsible for the breakdown and absorption of food to provide nutrients to the body.
- Organs Involved: Mouth, esophagus, stomach, small intestine, large intestine, liver, pancreas.
- Process: Food is broken down into simpler forms (digestion), absorbed into the bloodstream (absorption), and undigested food is excreted (egestion).
2.2. Circulatory System
The circulatory system transports nutrients, gases (oxygen and carbon dioxide), and waste products to and from the body’s cells.
- Organs Involved: Heart, blood vessels (arteries, veins, capillaries), blood.
- Process: The heart pumps oxygenated blood to tissues and deoxygenated blood to the lungs.
2.3. Respiratory System
The respiratory system is responsible for the exchange of gases (oxygen and carbon dioxide) between the body and the environment.
- Organs Involved: Nose, trachea, bronchi, lungs, alveoli.
- Process: Oxygen is taken in and transported to the bloodstream, while carbon dioxide is expelled from the body.
2.4. Excretory System
The excretory system removes metabolic waste products from the body and maintains water and salt balance.
- Organs Involved: Kidneys, ureters, bladder, urethra.
- Process: Kidneys filter blood to form urine, which is then excreted through the urethra.
2.5. Nervous System
The nervous system coordinates and controls the activities of the body by transmitting electrical signals.
- Organs Involved: Brain, spinal cord, nerves.
- Process: Sensory receptors detect stimuli and send signals to the brain, which processes the information and sends commands to effectors (muscles and glands).
2.6. Reproductive System
The reproductive system is responsible for the production of offspring.
- Organs Involved:
- In males: Testes, vas deferens, prostate gland, penis.
- In females: Ovaries, fallopian tubes, uterus, vagina.
- Process: In males, sperm is produced and transferred to the female reproductive system. In females, eggs are produced, and fertilization occurs in the fallopian tubes.
MCQs – Structural Organisation in Animals
1. Which type of epithelial tissue is responsible for absorption and secretion in the intestines?
a) Squamous Epithelium
b) Cuboidal Epithelium
c) Columnar Epithelium
d) Ciliated Epithelium
Answer: c) Columnar Epithelium
2. Which of the following tissues has a hard, calcified extracellular matrix?
a) Cartilage
b) Bone
c) Blood
d) Adipose tissue
Answer: b) Bone
3. Which of the following muscle tissues is striated and involuntary?
a) Skeletal muscle
b) Cardiac muscle
c) Smooth muscle
d) Both a and b
Answer: b) Cardiac muscle
4. The main function of red blood cells is to:
a) Fight infection
b) Carry oxygen
c) Regulate body temperature
d) Digest food
Answer: b) Carry oxygen
5. Which part of the neuron transmits impulses away from the cell body?
a) Dendrites
b) Axon
c) Soma
d) Synapse
Answer: b) Axon
6. The main function of the digestive system is:
a) Circulation of blood
b) Breakdown and absorption of food
c) Removal of waste products
d) Regulation of body temperature
Answer: b) Breakdown and absorption of food
7. Which of the following organs is responsible for filtering blood in the excretory system?
a) Heart
b) Lungs
c) Liver
d) Kidneys
Answer: d) Kidneys
8. The respiratory system is responsible for:
a) Transporting nutrients
b) Exchanging gases (oxygen and carbon dioxide)
c) Producing hormones
d) Removing waste
Answer: b) Exchanging gases (oxygen and carbon dioxide)
9. The central nervous system includes:
a) Nerves
b) Brain and spinal cord
c) Muscles
d) Glands
Answer: b) Brain and spinal cord
10. The reproductive system is responsible for:
a) Circulating blood
b) Producing offspring
c) Regulating metabolism
d) Producing digestive enzymes
Answer: b) Producing offspring