Human Anatomy And Physiology

Introduction

The human anatomy or the “body plan” that we possess now is the result of billions of years of evolution. If we were to “break apart” our body at the cellular level, then the cell would constitute the most basic unit, with an average adult having between 30 – 40 trillion cells. When a select group of cells with similar functions come together, it forms a tissue. In turn, tissues cumulate into organs, then organ systems and eventually, an organism.

Cells -> Tissues -> Organs -> Organ System -> Organism

Contents

 

Human Anatomy

The basic human body structure consists of a head, neck, four limbs that are connected to a torso. Giving the body its shape is the skeleton which is made of cartilage and bone. Human body organs, such as the lungs, heart and brain are enclosed within the skeletal system and are housed within various internal body cavities. The spinal cord connects the brain with the rest of the body.

Human Anatomy and Physiology

Human Anatomy is the scientific study of form and shapes of human beings 

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 distant common ancestor, we mostly have a body plan that is similar to other organisms, with just 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 precise.

One of our most prominent characteristics features is the ability to use our hands, especially for tasks that require dexterity, such as writing, 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 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 Physiology

It is referred to the physical, mechanical, and biochemical function of humans. This connects health, medicine, and science in a 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.

Read More: Physiology

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

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. There are essentially 2 components of circulation, namely:

  • Systemic circulation
  • Pulmonary circulation

Human Circulatory System

Diagram showing pulmonary (blue) and systemic circulation (red)

Besides these two, there is a third type of circulation called Coronary circulation. Because blood is the body’s connective tissue, it helps to transport essential nutrients and minerals to the cells and waste byproducts away from it. Hence, it is also known as the body’s “transport system.” Anatomically, the human heart is similar to other vertebrate hearts in the animal kingdom and hence, is a homologous organ.

Also Read: Double Circulation

Digestive System

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

Human Digestive System

A diagram of the human digestive system detailing various components

The major components of the digestive system are:

  • Mouth
  • Teeth
  • Tongue
  • Oesophagus
  • Stomach
  • Liver
  • Pancreas
  • Gastrointestinal tract
  • Small and large intestines
  • Rectum

The process of digestion starts with mastication (chewing food). Then, the saliva mixes with food and forms a bolus, a small rounded mass that can be easily swallowed. Once swallowed, the food travels down the oesophagus and into the stomach. The stomach secretes strong acids and powerful enzymes that break the food down into a paste.

It then moves into the small intestine where the food is broken down even more because of the bile secreted by the liver and powerful, digestive enzymes from the pancreas. This is the stage at which nutrients are absorbed from the food. The leftover materials (stool) then move on to the large intestine where it transforms from liquid to solid, as water is removed. Finally, it gets pushed into the rectum, ready to be eliminated from the body.

Explore: The Structure and Function of the Alimentary Canal

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.

Female Reproductive System

The female reproductive system consists of the following:

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

 

Female reproductive system

Male Reproductive System

The male reproductive system consists of testicles, which act as a storehouse for sperms. These oval-shaped organs are encased in a pouch that is called scrotum.

Male reproductive system

Next to the 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.

More to Explore: Reproductive System

Respiratory System

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

Vertebrates like human beings possess lungs for respiration. The process of respiration starts with the cycle of inhalation and exhalation. Inhalation results in the oxygen entering into the body and exhalation results in carbon dioxide exiting from the body. Anatomically, the respiratory system is comprised of the following organs:

  • Trachea
  • Bronchi
  • Bronchioles
  • Lungs
  • Diaphragm

 

Respiratory System

A diagram of the human respiratory system highlighting the gas exchange

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.

More About: Respiratory System

Nervous System

The voluntary and involuntary actions are maintained and taken care of by the central nervous system. It helps to channel the signals to and from different parts of our body. Nervous System is 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 includes nerves and ganglia that are present outside the brain and spinal cord. Through the axons, every part of the body gets connected.

Human Nervous System

Pictured: Distribution of Nerves in humans (top) and the Neuron (bottom)

Central Nervous System consists of:

  • 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, sexual development and emotions functions are attached to the forebrain.

  • Midbrain: It is situated between the hypothalamus and thalamus. The brain stem is associated with the midbrain. Auditory and visual responses are controlled by the midbrain.

  • 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 the spinal column are done by the Hindbrain.

Peripheral Nervous System consists of:

  • 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 the sensory organs, limbs and skeletal system. Imagine a scenario where you are riding a bicycle and suddenly, you spot an obstacle (say a dog) on the road. Your ability to immediately swerve out of the obstacle’s 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 the 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.

Further Reading: Nervous System

Key Points About the Human Body

Every living organism, organs, organ systems and tissues are made up of cells- the fundamental unit of life. Anatomy is the science of understanding the structure and the parts of living organisms.  Physiology, on the other hand, deals with the internal mechanisms and the processes that work towards sustaining life. These can include biochemical and physical interactions between various factors and components in our body. With the progress of evolution, organisms began to exhibit advanced characteristics and features that enabled them to be more efficient and thrive in their respective environment. The human structure can be described as bipedal, with hair covering the body, presence of mammary glands and a set of extremely well-developed sense organs.

With respect to human body anatomy, we have a specialized circulatory system enables the efficient transport of materials and nutrients within the body. The presence of a well-developed digestive system helps to extract essential nutrients and minerals required by the body. A well developed respiratory system ensures the efficient gas exchange and the nervous system enables coordination and interaction within the body and also the external environment, thereby ensuring survival.

Important Questions on Human Anatomy And Physiology

1. What is Anatomy?

Anatomy is the study of bodily structures and physical characteristics of organisms. It essentially pertains to the shape and form of an organism.

2. Define Physiology.

Physiology is the study of various processes, activities and functions that occur in an organism. Understanding these functions and how they help in sustaining life is the primary focus of physiology.

3. Name the two components of the Circulatory System.

  • Systemic circulation
  • Pulmonary circulation

4. State the parts of the digestive system.

  • Mouth
  • Teeth
  • Tongue
  • Oesophagus
  • Stomach
  • Liver
  • Pancreas
  • Gastrointestinal tract
  • Small and large intestines
  • Rectum

5. State the components of the Respiratory System

  • Trachea
  • Bronchi
  • Bronchioles
  • Lungs
  • Diaphragm

6. How is the nervous system classified?

The nervous system can be primarily classified into the following:

  • Central Nervous System (Brain + Spinal Cord)
  • Peripheral Nervous System (Nerves + Ganglia Outside the brain and spinal cord)

For more information about the human body, human body parts or any other related topic, please visit BYJU’S Biology.

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Practise This Question

Which of the following physical characteristics can be used to measure the level of water pollution