>INTRODUCTION
●What is a human body?
-A complex structure of cells,tissues,organs and systems which work altogether to support life.
-Cells:These are the smallest components in the body which holds individuality.
-Tissues: These are the group of cells that perform a specific function.
-Organs: These are the group of tissues that perform a specific function.
-Systems: These are the group of organs that perform a specific function.
-Many systems and mechanisms interact in order to maintain homeostasis, with safe levels of substances such as sugar, iron, and oxygen in the blood.
- It is very important to understand the human body because if reasons like:
• To make healthy choices.
•To recognize signs of illness.
• To communicate with healthcare providers.
-The external human body consists of a head, hair, neck, torso (which includes the thorax and abdomen), genitals, arms, hands, legs, and feet.
- The internal human body includes organs, teeth, bones, muscle, tendons, ligaments, blood vessels and blood, lymphatic vessels and lymph.
-The study of the human body includes anatomy, physiology, histology and embryology.
-The body varies anatomically in known ways. Physiology focuses on the systems and organs of the human body and their functions.
-The human body is composed of elements including hydrogen, oxygen, carbon, calcium and phosphorus. These elements reside in trillions of cells and non-cellular components of the body.
-Genetic materials
•Deoxyribonucleic acid (DNA): The hereditary master code that dictates each cell's operation and an individual's inherited characteristics
•Ribonucleic acid (RNA): Helps carry out the instructions encoded in DNA
>SKELETAL SYSTEM
-The internal framework of a human body which consists of bones connected by joints and ligaments.
-At birth,their are 270 bones which decreases to 206 bones as some gets fused together during adulthood.
-The total mass of bones constituting skeleton is the 14% of the body's total weight and it reaches to maximum mass during the age if 25 to 30.
-The Skeletal system of human beings is divided into:
•Axial skeleton: It is formed by vertebral column,rib cage,skull and other associated bones.
•Appendicular skeleton: It is formed by shoulder girdle,pelvic girdle and bones of upper and lower limbs. These bones are attached to the Axial skeleton.
-It performs six major functions:
•Gives support to the muscles.
•Help in movements of the body.
•Gives protection.
•Produce blood cells.
•Storage of minerals.
•Regulation of endocrine activities.
>MUSCULAR SYSTEM
-It is an organ system with three types of muscles which help in movement of body,circulation of blood and maintaining the body posture.
-The muscular and skeletal system work hand in hand in human body to help them in locomotion,jointly they are called musculoskeletal system.
-This system is controlled by nervous system in vertebrates,however some muscles like cardiac muscles are completely autonomous.
-The three types of muscles are as follows:
•Skeletal muscle: It is a type of striated muscle,composed of muscle cells called muscle fibers which in turn consist of myofibrils comprising the building blocks of this muscle tissue called sacromeres.
•Cardiac muscle:It is a striated muscle but different from skeletal muscle because the muscle fibers are laterally connected. Furthermore, just as with smooth muscles, their movement is involuntary. Heart muscle is controlled by the sinus node influenced by the autonomic nervous system.
•Smooth muscle:Their contraction is regulated by the autonomic nervous system, hormones, and local chemical signals, allowing for gradual and sustained contractions. This type of muscle tissue is also capable of adapting to different levels of stretch and tension, which is important for maintaining proper blood flow and the movement of materials through the digestive system.
>NERVOUS SYSTEM
-It is a highly complex part which coordinates actions and sensory information by transmitting signals in a human body.
-It detects the environmental changes affecting the body and help the body to respond to such events.
-It consists of two main parts"
•Central nervous system(CNS): It constitutes Brain,Spinal cord. This system is connected to the body by motor nerves(transmit signals from brain to the body) and sensory nerves (transmit signals from body to brain).
•Peripheral nervous system(PNS): It consists mainly of nerves enclosed in bundle of long fibres called axons. The motor and sensory nerve mentioned above connect CNS to every part of the body.
It is divided into two separate subsystems, the somatic and autonomic, nervous systems.
The autonomic nervous system is further subdivided into the sympathetic, parasympathetic and enteric nervous systems.
The sympathetic nervous system is activated in cases of emergencies to mobilize energy.
The parasympathetic nervous system is activated when organisms are in a relaxed state.
The enteric nervous system functions to control the gastrointestinal system.
Nerves that exit from the brain are called cranial nerves while those exiting from the spinal cord are called spinal nerves.
>CIRCULATORY SYSTEM
- It is a system of organs which includes heart,blood vessels and blood that is circulated throughout the body.
-It is also called a cardiovascular system, derived from a Greek word kardia meaning heart and a Latin word vascula meaning vessels.
-It has two divisions:
•Systemic circulation
•Pulmonary circulation
- The blood vessels of the heart includes large elastic arteries, and large veins; other arteries, smaller arterioles, capillaries that join with venules (small veins), and other veins.
- The circulatory system is closed in vertebrates, which means that the blood never leaves the network of blood vessels.
-Blood is a fluid consisting of plasma, red blood cells, white blood cells, and platelets; it is circulated around the body carrying oxygen and nutrients to the tissues and collecting and disposing of waste materials.
-Circulated nutrients include proteins and minerals and other components include hemoglobin, hormones, and gases such as oxygen and carbon dioxide.
- These substances provide nourishment, help the immune system to fight diseases, and help maintain homeostasis by stabilizing temperature and natural pH.
-Another circulatory system known as the lymphatic system is complementary to the cardiovascular system. It carries excess plasma (filtered from the circulatory system capillaries as interstitial fluid between cells) away from the body tissues via accessory routes that return excess fluid back to blood circulation as lymph.
-The lymphatic system is a subsystem that is essential for the functioning of the blood circulatory system; without it the blood would become depleted of important nutrients.