Unit 2  

INTRODUCTION TO THE  DETAILED OF THE BODY 



Q1. Define a cell. Describe the structure and functions of a cell in detail.

Answer

Definition : A cell is the smallest structural and functional unit of the human body. All body tissues and organs are made up of cells.
> According to p .v. pillai : a cell is the smallest unit of the human body .
> cell is the basic living unit that performs all life activities 

Structure of a Cell:
 The cell consists of three main parts:

1. Cell Membrane
a. Thin, elastic outer covering of the cell
b. Also known as plasma membrane

Functions:
a. Protects the cell
b. Maintains the shape of the cell
c. Controls entry and exit of substances (selectively permeable)

2. Cytoplasm
a. Semi-fluid substance present inside the cell membrane
b. Contains various cell organelles

Functions :

a. Site of metabolic activities
b. Provides support to cell organelles

Cell Organelles and Their Functions :

Mitochondria: Powerhouse of the cell; produces energy
Ribosomes: Protein synthesis
Endoplasmic reticulum: Transport of materials
Golgi apparatus: Packaging and secretion
Lysosomes: Digestion of waste materials (suicide bags)
Centrioles: Help in cell division

3. Nucleus
Control center of the cell
Contains genetic material (DNA)

Functions
> Controls all cell activities
> Responsible for cell division
> Transmits hereditary characters


Functions of a Cell :

Respiration: Produces energy required for cellular activities
Growth: Increases size and number of cells
Excretion: Removes waste products from the cell
Reproduction: Formation of new cells by cell division
Movement: Allows movement of substances within the cell and body
 Repair: Helps in healing and replacement of damaged cells


Q2. Describe the cell, tissues, and body cavities with their functions and examples.

Answer: The human body is composed of cells, tissues, and organs. Cells form tissues, tissues form organs, and organs are located within body cavities.

1. Cell
 Definition :A cell is the smallest structural and functional unit of the human body.

Parts of a Cell :
Cell membrane: Protects the cell and regulates entry and exit of substances
Cytoplasm: Contains cell organelles and performs metabolic activities
Nucleus: Controls cell activities and contains genetic material

Functions of a Cell :
Respiration
Growth
Excretion
Reproduction
Movement
Repair

2. Tissues
  Definition: A tissue is a group of similar cells performing a specific function.

Types of Tissues
Epithelial tissue: Protection, absorption, secretion
Connective tissue: Support and binding
Muscular tissue: Movement
Nervous tissue: Transmission of nerve impulses

3. Body Cavities

Definition: Body cavities are spaces within the body that protect and support internal organs.

Types of Body Cavities and Contents

Cranial cavity: Brain
Spinal cavity: Spinal cord
Thoracic cavity: Heart and lungs
Abdominal cavity: Stomach, liver, intestines
Pelvic cavity: Urinary bladder and reproductive organs

Q3. Explain in detail the structure of the cell, classification of tissues, and body cavities with their contents.

Answer: 

1. Structure of a Cell
Cell membrane
Cytoplasm
Nucleus

Cell organelles such as mitochondria, ribosomes, Golgi apparatus, and lysosomes perform essential cellular functions.


2. Classification of Tissues
Epithelial Tissue
Covers body surfaces
Example: Skin

Connective Tissue
Provides support and protection
Example: Bone, blood

Muscular Tissue
Helps in movement
Types: Skeletal, smooth, cardiac

Nervous Tissue
Transmits nerve impulses
Found in brain and spinal cord


3. Body Cavities and Their Contents
 
Dorsal cavity: Brain and spinal cord
Thoracic cavity: Heart and lungs
Abdominal cavity: Digestive organs
Pelvic cavity: Excretory and reproductive organs