See here detailed information about human body parts and their functions

human body parts

The anatomy and physiology of humans is more complex than that of other living beings. Our body is made up of different organ systems that work together to keep us alive and healthy. Each organ system has its own specific function, and they all need to work together for our bodies to function properly.

It is important to understand how the organ systems of the human body work so that we can take better care of ourselves. By understanding how our body works, we can make better choices about our diet, exercise, and lifestyle.

1. Muscular and skeletal system

The skeleton is either a fluid-filled body cavity, an exoskeleton, or internal bone. Bones, joints and muscles are part of the skeletal system of humans. The skeletal system is composed of 2 parts:

• axial bones- Bone that forms the main axes of the body such as the bones of the skull, vertebral column, and chest.
• appendages- It includes the bones that support the appendages.

Points to note:

• There are 118 bones in both hands and feet.
• The total number of bones in the human body is 206.
• The total number of bones in childhood is 300.
• The total number of bones in the head is 29.
• The largest bone of the body is the femur (thigh bone).
• The smallest bone in the body is the stapes.
• Tendon connects muscle and bone together.
• The muscle that connects bones to bones is called ligament.
• The ligaments of the human body are made of yellow fibres.

2. Nervous system

Within the nervous system, nerves that transmit signals and electrical impulses to respond to external changes are spread throughout the body. The nervous system includes:

• The central nervous system (CNS) includes the brain and spinal cord.
• The peripheral nervous system (PNS) connects the CNS to other parts of the body, and is composed of nerves (bundles of neurons).
• Autonomic Nervous System

Central Nervous System (CNS)

The CNS controls the entire body and is made up of two parts: the brain and the spinal cord.

Brain

The brain is the most complex part of the human body. This three-pound organ is the seat of intelligence, the perceiver of the senses, the initiator of body movement and the controller of behavior. The brain can be divided into three basic units:

• forebrain- The forebrain is the largest and primarily the thinking part of the brain. It contains areas that receive sensory impulses from various receptors. Different parts of the forebrain are for special functions like hearing, smell, vision etc.
• midbrain- Connects the forebrain to the hindbrain.
• hindbrain- The hindbrain controls vital body functions such as respiration and heart rate.

cerebrum

The cerebrum is a vital part of the human brain that controls our conscious experiences, sensory perception, motor control, and higher cognitive functions. It plays a fundamental role in shaping our behavior, thoughts and memories.

• This is the largest part of the human brain.
• It is located in the uppermost part of the brain.
• It is the source of intellectual activities.
• It keeps your memories, allows you to plan, and lets you
• Enables to imagine and think.
• It controls voluntary motor actions.

hypothalamus

It acts as a link between the nervous system and the endocrine system, ensuring proper hormonal balance and coordinating functions necessary for overall well-being.

• It is situated at the base of the cerebrum.
• It regulates the body’s sleep and wake cycles (circadian rhythm).
• It also controls the desire to eat and drink.

cerebellum

The cerebellum is an important part of the brain responsible for motor control, coordination, balance, and motor learning. It works in conjunction with the cerebrum and other brain areas to enable the smooth and precise movements needed for daily activities. It is located below the cerebrum and behind the entire structure.

medulla

The medulla oblongata, commonly called the medulla, is an important part of the human brain. It is located at the base of the brain, acting as a connection between the spinal cord and the rest of the brain. Its primary role revolves around regulating vital functions and facilitating the transmission of sensory and motor information between the brain and spinal cord.

thalamus

• A major clearinghouse for information going to and from the spinal cord and cerebrum.
• Cerebrospinal fluid (CS(F)) is a watery fluid that circulates through the ventricles (cavities or hollow spaces) of the brain and around the surface of the brain and spinal cord.

3.Transmission system

The circulatory system is responsible for the circulation of blood throughout the body for proper functioning. There are 4 parts under this:

• Heart
• artery
• Vein
• blood

human heart

The human heart is an organ that pumps blood throughout the body through the circulatory system, supplying oxygen and nutrients to tissues and removing carbon dioxide and other wastes. The human heart consists of four chambers:

• The right atrium and right ventricle together make up the “right heart”.
• The left atrium and left ventricle together make up the “left heart”.
• A muscular wall called the septum separates the right and left atrium.
• Valves prevent backflow, keeping blood from the heart flowing in only one direction.
• A double-walled sac, called the pericardium, surrounds the heart, protecting it and supporting it inside the chest.
• Pericardial fluid flows between the outer layer, the parietal pericardium, and the inner layer, the serous pericardium, which lubricates the heart during the contraction and expansion of the lungs and diaphragm.
• The outer wall of the heart has three layers:-
  – The outermost wall layer or epicardium is the inner wall of the pericardium.
  – The middle layer or myocardium contains muscles that contract.
  – The inner layer, or endocardium, is the lining that contacts the blood.
• The sinoatrial node produces the electrical impulse that drives the contraction of the heart.

human heart function

The heart circulates blood through two routes:
1. Pulmonary Circuit
2. Systemic Circuit

• In the pulmonary circuit, deoxygenated blood leaves the right ventricle of the heart through the pulmonary artery and travels to the lungs, then returns as oxygenated blood to the left atrium of the heart through the pulmonary artery.
• In the systemic circuit, oxygenated blood passes through the body from the left ventricle to the aorta, and from there to the arterioles and capillaries where it supplies the body’s tissues with oxygen. Deoxygenated blood flows through the veins into the vena cava and, again, enters the right atrium of the heart.

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important point:-

• aorta-The largest artery of the body. It transports oxygen-rich blood from the heart to the rest of the body.
• atria- The chambers of the heart from which blood returns after circulation.
• Capillary- The smallest of the blood vessels in the body. Oxygen and glucose pass through the capillary walls and enter the cells. Waste products such as carbon dioxide return from the cells to the blood through capillaries.
• Cardiac Valve (Heart Valve) – Any of the four heart valves, which control the flow of blood through the chambers of the heart.
• oxygenated blood – oxygenated blood
• deoxygenated blood- low oxygen blood
• Heart ventricles – right and left chambers of the heart
• interventricular septum There is a stout wall separating the lower chambers (ventricles) of the heart from each other.
• lung- One of a pair of organs in the chest that supply oxygen to the body, and remove carbon dioxide from the body.
• myocardium– muscular substance of the heart; In between the three layers is the outer wall of the human heart.
• pulmonary artery– The pulmonary artery and its branches deliver blood enriched with carbon dioxide (and deficient in oxygen) to the capillaries that surround the air sacs.
• pulmonary circulation– circulation of blood through the lungs
• Pulmonary veins – Veins that deliver oxygenated blood from the lungs to the left atrium of the heart.
• superior vena Cava – The large vein that carries blood from the head, neck, arms and chest to the heart.
• vena cava- A large vein that supplies blood from the head, neck, and extremities to the heart.

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4. Digestive system

The human digestive system is a coiled, muscular tube (6–9 meters long when fully extended from the mouth to the anus).

mouth and pharynx
Chemical breakdown of starch into glucose by the production of salivary amylase from the salivary glands. This mixture of food and saliva is then passed into the pharynx and esophagus.

stomach

Gastric juice of the stomach contains:
• Hydrochloric acid(HCl),
• Pepsinogen and
• Mucus
Functions of Hydrochloric Acid(HCl):

• it kills microorganisms
• It reduces the pH of the stomach to between 1.5 to 2.5.
• It lowers the pH of the stomach which activates pepsin.
• Pepsogen is an enzyme that initiates protein digestion and controls the hydrolysis of proteins to form peptides.
• Chyme, a mixture of stomach acid and food, leaves the stomach and enters the small intestine.
• Alcohol and aspirin are absorbed through the stomach lining in the stomach. Epithelial cells secrete mucus that forms a protective barrier between the cells and stomach acid.

small intestine
The small intestine is the major site of digestion and absorption of nutrients.

• It grows to about 22 feet (6.7 m) long.
  Parts of small intestine:
  1. Duodenum
  2. Jejunum
  3. Ileum
• Sugars and amino acids move into the bloodstream through capillaries in each villus.
• Glycerol and fatty acids pass into the lymphatic system.
• Starch and glycogen are broken down into maltose by enzymes of the small intestine.
• Maltose, sucrose, and lactose are the main carbohydrates present in the small intestine; They are absorbed by microvilli.

5. Excretory system

The urinary system is composed of the kidneys, ureters, urinary bladder, and urethra. Nephron, an evolutionary modification of nephridium, is the functional unit of the kidney.

Nephron has three functions:
1. Glomerular filtration of water and solutes from the blood
2. Tubular reabsorption of water and release of conserved molecules into the blood.
3.Tubular secretion of ions and other waste products from surrounding capillaries into the outer capillaries.

6. Endocrine system

The endocrine system is made up of glands that produce and secrete hormones, chemical substances produced in the body that control the activity of cells or organs. These hormones control body growth, metabolism (physical and chemical processes of the body), and sexual development and function.

Adrenal gland

The adrenal glands (also known as suprarenal glands) are endocrine glands that produce a variety of hormones, including adrenal. These are found above the kidneys.

hypothalamus

The hypothalamus is a part of the brain that contains small nuclei with a variety of functions.
Function: Connecting the nervous system to the endocrine system through the pituitary gland.

pituitary gland

The pituitary gland (often called the master gland) is located in a small bony cavity at the base of the brain. It is an endocrine gland the size of a pea and weighing 0.5 grams in humans. Hormones secreted from the pituitary gland help control the following:
• Development,
• blood pressure,
• Some functions of sexual organs,
• metabolism,
•Pregnancy,
• delivery,
• Nursing,
• Water/salt concentration,
• temperature control
• Pain relief

Thyroid

The thyroid gland, or simply thyroid, is one of the largest endocrine glands in the body. It is found in the inner neck, below the Adam’s apple.

• It secretes two hormones: triiodothyronine (T3) and tetraiodothyronine (T4), which are called tyrosines. Both hormones contain iodine.
• Hypothyroidism (hypo, ‘under’) – reduced thyroid activity. Hypothyroidism in childhood leads to a condition called cretinism.
• Regulates the rate of utilization of energy sources, protein synthesis, sensitivity of the body to other hormones.
• Goiter – This is called enlargement of the thyroid gland. This occurs in the form of swelling in the neck. A goiter may be associated with enlargement, normal or reduced, of the thyroid gland and some activity.
  

  pancreas

The pancreas is a glandular organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdominal cavity behind the stomach. It produces several important hormones:
• Insulin,
•Glycogen,
• Somatostatin, and
• Pancreatic polypeptide which circulates in the blood.
The pancreas is also a digestive organ, which secretes pancreatic juice along with digestive enzymes, which aid in the absorption of nutrients in the small intestine.

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