Human Anatomy - Human Body Parts and Systems


The human anatomy or the “body plan” that we possess now is the result of millions of years of evolution. Now, when we look at ourselves in a mirror, we could name our body parts like the head, neck, chest, abdomen, trunk, hands, legs, feet etc. But behind all these complex parts, lies the most basic and fundamental structure called the cell.

The basic build-up of our organs would be like Cells -> Tissues -> Organs -> Organ System -> Organism.

Levels of organization

Anatomy:

The basic human body structure consists of a head and neck, four limbs that are connected to a torso. Giving the body its shape is the skeleton which is made of cartilage and bone. The spinal cord connects the brain with the rest of the body. Then there are cavities in the human body that house various organs systems. The skull protects the brain and part of the central nervous system. The lungs are protected in the pleural cavity. The abdominal cavity houses the intestines, liver and spleen. Humans have evolved separately from other animals but since we share a common ancestor, we mostly have a similar body plan with the muscles and bones in different proportions. For example, you might assume giraffes have more vertebrae in its neck than us humans. But you’d be wrong because even though a giraffe’s neck is obviously longer, they have the same number of vertebrae as us: 7 to be exact.

One of the most important characteristics that defines us is our ability to use our hands for tasks that require dexterity, such as writing with a pen, opening a bottle of water, opening a door knob etc. This is the result of humans having ancestors that began walking on their hind limbs rather than using all four limbs.

Most of our anatomical insight was gained through the dissection of corpses (cadavers), and for a long time, it was the only way we could gain anatomical knowledge about the human body. It was a rather grotesque affair but it made up the bulk of medical literature for centuries. These days, technological innovation has made it possible to explore the human anatomy at a microscopic level. Even to this day, scientists are new discovering organs that were previously overlooked or have been mistakenly identified as other existing tissues. In 2018, scientists had discovered a new body-wide organ called the Interstitium that exists right under the skin.

Human anatomy

Human Physiology

It is referred to the physical, mechanical, and biochemical function of humans. This connects health, medicine, and science in the way that studies how the human body acquaints itself to physical activity, stress, and diseases.

The person who is trained to study human physiology is called a physiologist. Herman Boerhaave is referred to as the father of physiology for his exemplary research and teaching during 1708.

Let’s study what are the important parts of the human body:

  • Circulatory system

Circulatory system

The circulatory system is also referred to as the cardiovascular system. It comprises the heart and all the blood vessels: arteries, capillaries, and veins. Besides carrying blood from tissues to blood vessels and back, it also acts as the “body’s transportation system” because it helps to transfer oxygen and nutrients to body and then waste byproducts away from the body.

  • Digestive system

The digestive system breaks down food and assimilates nutrients into the body, which then the body uses for growth and cell repair.

The components of the digestive system are:

  • The mouth
  • Teeth
  • Tongue
  • Esophagus
  • Stomach
  • Liver
  • Pancreas
  • Gastrointestinal tract
  • Small and large intestine
  • Rectum.

The process of digestion starts as soon as we take a bite and begin chewing. The saliva mixes with food and forms a bolus, a small rounded mass that can be easily swallowed. Once you swallow, the food travels down the esophagus and into your stomach. The stomach secretes strong acids and powerful enzymes that break the food down into a paste. It then moves on to the small intestine where the food is broken down more by using bile created by the liver and powerful enzymes from the pancreas. This is the stage at which nutrients are absorbed from the food. The leftover materials (stool) then moves on to the large intestine where it transforms from liquid to a solid, as water is removed. Finally, it gets pushed into the rectum, ready to be eliminated from the body.

Digestive system

  • Human Reproductive System

The human reproductive system is also known as the genital system that comprises of internal and external organs that help in reproduction. It varies for both males and females.

Hormones, fluids, and pheromones are all connective accessories for the reproductive organs to function.

  • The female reproductive system:

Female reproductive system

Ovaries: Produces ovum – female egg as well as the hormone estrogen.

Uterine tubes: Oviducts or fallopian tubes are the other names given for uterus tubes. Popularly known as the womb, the Uterus is the pear-shaped organ that is considered as the home for the fetus to grow. The cervix is the route to vagina and gateway for sperm to enter. Vagina acts as the route for a penis to enter during intercourse as well as the fetus to deliver.

The Male reproductive body parts are:

Male reproductive system

The male reproductive system consists testicles as one of the prime members that act as a storehouse of sperms. These oval-shaped organs are a encased in a pouch that is called scrotum. Next to testis is the vas deferens that are the accessory ducts for the male sexual system. When sperm is formed, it is mixed with fluids that are produced by seminal glands, prostate gland, and Cowper’s gland. The main purpose of Cowper gland is to hike the semen volume and lubrication during coitus.

  • Respiratory System:

The respiratory process basically involves the intake of oxygen and exhale of carbon dioxide from our body. This system is also known as the ventilatory system, gas exchange system or respiratory apparatus.

Invertebrates like human beings, lungs are the organs with which respiration takes place.

Respiration starts with the cycle of inhalation and exhalation. By inhalation, we mean the passage from where the oxygen enters into the body and by exhalation we mean the passage through which carbon dioxide exits from the human system. Anatomically speaking, respiratory organs include:

Respiratory System

  • Trachea,
  • Bronchi,
  • Bronchioles,
  • Lungs
  • Diaphragm

By diffusion, molecules of carbon dioxide and oxygen are exchanged passively among the blood cells and external environment. This swap is done through alveoli (which are the air sacs) in the lungs.

  • Nervous System

The voluntary and involuntary actions are maintained and taken care by the central nervous system. It helps to channel the signals to and from different parts of our body. Nervous Systemis broadly classified into two categories :

  • Central Nervous System
  • Peripheral Nervous System

The central nervous system contains the brain and the spinal cord while the peripheral nervous system include nerves that are enclosed with bundles of long fibers and axons. Through the axons, every part of the body gets connected.

The Central Nervous system consists of:

Central Nervous System

  • The forebrain: It comprises of the cerebrum, hypothalamus, and thalamus. The largest part of the brain is the cerebrum. Thinking, perceiving, controlling motor function, receiving and processing information and understanding language are the main functions done by this section of the brain.Also, the sexual development and emotions functions are attached to the forebrain.
  • The Midbrain: It is situated between the hypothalamus and thalamus. The brain stem is associated with midbrain. Auditory and visual responses are controlled by midbrain.
  • The Hindbrain: The medulla, pons, and cerebellum are together tied in the hindbrain. Interconnections of different parts of the brain’s surface that helps to accommodate neurons and connect them to spinal column are done by the Hindbrain.

The peripheral nervous system consists of:

Peripheral Nervous System

  • Somatic nervous system: The system’s main purpose is to transmit the motor and sensory impulses from CNS and back. It is linked to all your sensory organs, your limbs and your skeletal system. Imagine a scenario where you are riding a bicycle and suddenly, you spot an obstacle (say a dog) on road. Your ability to immediately swerve out of the obstacles path and avoid the crash is the result of the somatic nervous system taking action.
  • Autonomic Nervous System: This system works without the person’s effort. The system helps to relay impulse from central nervous system to smooth muscles and involuntary organs such as your heart, lungs etc. Also, it prepares the body against any violent attacks or abnormal conditions such as high body temperature during a fever or high rate of breathing and blood pressure after a strenuous exercise.

For more information about the human body, visit Byju’s.


Practise This Question

Sperm always carries a Y chromosome.