Introduction To Human Body
Introduction To Human Body
CHAPTER PREVIEW
Levels of Structural organization
Body's Organ Systems
Major Regions of Human Body
Basic Life Functions
Survival Needs of Human Body
Internal Environment and Homeostasis
Learning Outcome
1. What are the different functional systems of the body
2. What are the major organs and general functions of each organ system
3. Name the basic life functions or processes
4. Outline activities undertaken by an individual body for survival
5. Define the terms internal environment and homeostasis
LEVELS OF STRUCTURAL ORGANIZATION
The human body is complex, so it consists of several levels of structural organization. From the smallest to the largest, six levels of organization are relevant to understand Anatomy and Physiology:
1. Chemical level
2. Cellular level
3. Tissue level
4. Organ level
5. Organ system level
6. Organismal level
The chemical and cellular levels are the basic structural and functional levels.
• Chemical level:
It is the lowest level in which atoms (the fundamental building blocks of chemicals) combine to form molecules such as water and proteins.
• Cellular level:
Cells are the basic structural and functional units of the body, because all of the processes of life occur within cells. The body is composed of many different types of cells, such as blood cells, muscle cell, nerve cells etc. Cells with similar structure and functions are bound together as tissues.
• Tissue level:
A tissue is an aggregation of similar cells bound by matrix and performs a particular function.
There are just four basic tissue types in the body-
1. Epithelial tissue (epithelium) covers the body surface and lines its cavities.
2. Connective tissue binds, supports, and protects body organs.
3. Muscle tissue provides movement.
• Organ level:
Organs are made up of a number of different types of tissue and perform a specific function for the body.
The vital body organs are those that are essential for critical body functions. Examples of organs are heart, liver, kidneys, lungs and brain.
• Organ system level:
Organ systems consist of a number of organs, arranged in functional groups that together contribute to perform a common system functions. For example, the heart and blood vessels of the cardiovascular system always circulate blood to carry oxygen and nutrients to all body cells.
• Organismal level:
It is the highest organizational level. All the parts of human body working together contribute to total organism.
BODY'S ORGAN SYSTEMS
• What are the different functional systems of the body?
There are eleven functional organ systems in human body as follows:
1. Integumentary system
2. Skeletal system
3. Muscular system
4. Nervous system
5. Endocrine system
6. Cardiovascular system
7. lymphatic system
8. Respiratory system
9. Digestive system
10. Urinary system
11. Reproductive system
Neck:
The head houses the upper parts of the digestive and respiratory tracts.
Thorax:
Its wall is made of bony framework and is separated from the abdomen inferiorly by the diaphragm. It houses the lungs, heart, trachea, oesophagus, aorta, superior and inferior vena cava, thoracic duct and lymph nodes.
Abdomen:
The abdomen is the biggest cavity in the body below the diaphragm, which is arbitrarily divided into abdomen proper and pelvis.
Upper and lower limbs :
The two pairs of limbs are- upper limbs and lower limbs, both are built on the same basic principle.
Each limb is made up of a basal segment or girdle (shoulder girdle in upper limb and pelvic girdle in lower limb), and a free part divided into proximal, middle, and distal segments.
Homologous parts of the limbs
Upper limb
1. Shoulder girdle
2. Shoulder joint
3. Arm with humerus
4. Elbow joint
5. Forearm with radius and ulna
6. Wrist joint
7. Hand with
(i) Carpus
(ii) Metacarpus
(iii) 5 digits
Lower limb
1. Hip or pelvic girdle
2. Hip joint
3. Thigh with femur
4. Knee joint
5. Leg with tibia and fibula
6. Ankle joint
7. Foot with
(i) Tarsus
(ii) Metatarsus
(iii) 5 digits
BASIC LIFE FUNCTIONS
The highly organized human body does many functions for survive.
Basic Life Functions
1. Maintains boundaries
• Separate the internal and external environments.
2. Moves
• Locomotion.
• Change body and body part positions.
3. Responds and reacts
• Behavioral reactions and responses.
• Physiological responses to stimuli.
4. Ingests and digests nutrients
5. Eliminates wastes
6. Reproducts
7. Grows
SURVIVAL NEEDS OF HUMAN BODY
life is extraordinarily fragile and requires many factors for survive.
1. Food
• Food is ingested and processed by the digestive system.
2. Oxygen
• Required for the breakdown of nutrients to harvest energy.
3. Water
• Lost due to evaporation or excretion.
4. Body temperature
5.Atmospheric pressure
INTERNAL ENVIRONMENT AND HOMEOSTASIS
Homeostasis is maintained by control mechanisms that detect and respond to changes in the
internal environment.
Negative feedback mechanisms
The negative feedback mechanisms reduce the original stimulus, and are essential for maintaining homeostasis.
Positive feedback mechanisms
The positive feedback mechanisms intensify the initial stimulus, leading to an enhancement of the response.
CHAPTER SUMMARY
Levels of Structural Organization
Body's Organ Systems
Major Region of Human Body
The body has two major parts namely axial part and appendicular part. The axial part head, neck, and trunk (thorax and abdomen). The appendicular part consists of upper limbs and lower limbs.
Basic Life Functions
The human body performs certain vital functional activities necessary for life, including movement, responsiveness, digestion, metabolism, excretion, reproduction, and growth.
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