Human Body Anatomy

The human body is made up of millions and trillions of cells. The cell is the basic unit of life. In every individual or organism, a cell constitutes the basis of their morphology. Many cells unite to form a tissue. Many similar tissues come together to form an organ. Many organs constitute an organ system and thus an individual.

The study of the human body comprises of-

1. Anatomy - Involves the study of structure and parts of the human body.

2. Physiology - Involves the study of chemical and physical functions carried out by organs and cells in a human body.

3. Histology - Involves the study of the anatomy of cells and tissues.

4. Embryology - Involves the study of gametes formation, embryo development, and also the study of congenital diseases. 

Human Anatomy

The branch of biology that deals with the study of structure and parts of the human body is called Human Anatomy. The Study of anatomy is further divided into two sections. The first section is called Gross Anatomy and deals with the study of structures that can be seen without a microscope. The second section deals with the study of structures that are microscopic and need to be examined under a microscope.

Human Body Parts- A human body consists of a head, neck, trunk, arms, and legs.

Skeleton

The skeleton is a framework of bones, ligaments, and cartilages that gives the body shape. Apart from giving shape, the spinal cord that runs along the human body connects the brain to other parts of the body.

Also, it provides a protective casing for vital organs in our bodies. Like the thoracic cage for lungs, the skull for the brain, etc.

Every adult human being has 206 bones in the body. During birth, we have 300 bones, but as we grow up, these bones fuse to form a framework and thus leaving 206 bones in total.

There are also a few vestigial bones in the human body that have no use now. Over the course of evolution, they are no more functional or have any specific purpose, but we still have them. Example- Coccyx or the tail bone. 

The bones and cartilages in our body are connected by Connective tissue- ligaments and tendons. Bones in the human skeleton are divided into

1. Axial Skeleton - Bones of the skull and trunk of vertebra form the axial skeleton. Out of the total of 206 bones, 80 bones constitute the axial skeleton. The bones in the axial skeleton include- Vertebra, Coccyx, Sacrum, Ribs, and Sternum.

Its basic function is to provide protection to the internal organs. As it surrounds the vital organs like the brain, lungs, heart, etc. The axial skeleton also consists of the ear ossicles and Hyoid bone in the neck.

2. Appendicular Skeleton - The bones that help in movement and locomotion are part of the appendicular skeleton. These bones are movable and possess flexibility.

Apart from providing support, facilitating locomotion, and providing protection to vital organs, bones also aid blood cell production. The bone marrow present inside the bone has stem cells, which are responsible for the production of red blood cells, and they also store white blood cells. 

Muscles

Muscles are an inseparable part of our body and are attached to bone through the tendons. They help us in locomotion along with the bones. They help in the movement of the body, maintain posture, and help circulate blood throughout the body. Not only for locomotion, but muscles also aid the movement of internal organs. Example- Contraction of the heart is facilitated by muscles. 

Human Body - Structural Levels of Organization

There are several levels of organization that our body goes through to carry out different processes. All the lower-level organizations lay the foundation for the bigger level organizations. 

i) Chemical Level - Molecules from different elements like hydrogen, carbon, oxygen, and so on form the living matter of the cell. At this level, we are talking about the formation of molecules of protein, water, sugar, etc.

ii) Cell-Level - Cell is the basic unit of life and all organisms are composed of a cell. There are single-celled organisms as well, living on Earth. As far as Human Anatomy is concerned, many such cells constitute a tissue.

iii) Tissue Level - When many tissues, similar to each other help carry out a function, they form an organ.

iv) Organ Level - When many tissues work together to form an organ, it carries out a particular function in the human body.

v) Organ System Level- Many organs of the same type, carrying out a single process is called Organ System Level.

vi) Organism Level - Organ systems, carrying out different processes, constitute an organism or individual.

Human Physiology

Human Physiology refers to the study of functions of organ systems and mechanisms that these organ systems follow. Thus, the main objective of a Physiological study is to focus on different organ systems, organs, tissues, cells, and also the chemical level of the organization carrying out a process in the human body. Human Physiology is a very important part of the study because it focuses on the working and mechanism of the human body.

A human body consists of roughly 79 organs, discovered to date. Each of these organs forms an organ system to carry out the most crucial process necessary for continuity of life.

The Major Systems under Human Physiology are discussed below:

We have already covered the Skeletal and Muscular systems. Let’s get into the details of other physiological systems.

1. Circulatory System

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The heart and blood vessels constitute the circulatory system. The circulatory system is a network of arteries, capillaries, and veins all connected by the heart to supply oxygen and nutrients to different parts of the body. Another function of this system is to carry away waste products. The circulatory system maintains homeostasis by maintaining the temperature of the body.

The circulatory system carries out three types of circulation. Blood is the carrier in the circulatory system. Blood carries nutrients, oxygen, and wastes throughout the body.

a) Systemic Circulation - Involves the supply of functional blood carrying oxygen and nutrients to all tissues of the body.

b) Pulmonary Circulation - Involves the transport of deoxygenated blood from ventricles to the lungs and returns oxygenated blood.

c) Coronary Circulation - The coronary circulation circulates the blood around the heart. This system supplies oxygenated blood to the heart muscles. And, takes deoxygenated blood away.

2. Digestive System

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The digestive system and excretory system work together simultaneously. The digestive system absorbs nutrients from the food we eat and supplies it to the body and the excretory system helps the body get rid of the waste generated in the process. Every part involved in the digestive system helps the movement of food through the gastrointestinal tract, breaking the food into molecules and absorption of nutrients. The digestion process starts right when we are chewing our food. Thus, the first organ involved in this process is the mouth. The process of chewing food is called mastication, once mastication is over, the food is mixed with saliva and forms a goblet called the bolus. The bolus then travels into the stomach through the esophagus.

The stomach is the storehouse of acids and enzymes that breaks down the food. The broken-down food is then mixed with the bile juices in the pancreas and nutrients are absorbed from the food. Finally, the waste generated in the process is moved into the intestines where it is taken over by the exocrine system and eliminated by the body.

3. Respiratory System

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The aim of the respiratory system is to absorb oxygen and remove carbon dioxide from the body. The primary organ of the respiratory system is a pair of lungs. As we breathe, lungs exchange glasses thus carrying out the process of respiration. Respiratory System and circulatory system work together to pump oxygenated blood throughout the body. As we breathe, the air passes from the nose to the sinuses that help to regulate the temperature of the air. The air then travels through the windpipe, also called trachea. The air from the trachea passes into the bronchial tubes. The bronchial tubes have a lining of cilia that carries mucous. Mucous is a sticky fluid that forms the first barrier, collecting dust and other small foreign particles from the air we breathe. The lungs and heart then turn the deoxygenated blood into oxygenated blood and pump it throughout the body.

4. Urinary System

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The urinary system consists of the pair of kidneys, connected by ureters to the bladder and opening into the urethra. The urinary system eliminates wastes from the body in the form of urine. Apart from this, it also checks blood pressure, regulates the levels of metabolites and electrolytes, and regulates the pH of the blood. Kidneys receive blood through the renal arteries to the nephrons in the kidneys. Nephrons carry out the purification of blood and subsequently formation of urine, which then leaves the kidneys through the renal veins and is eliminated from the body in the form of urine.

Normally, a healthy human produces 800- 2000 ml of urine per day.

5. Immune System

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The immune system is the defense mechanism of the body that protects the body against diseases. And it keeps the record of the invaded pathogens so that it can combat the pathogen when it comes in contact again. The immune system produces immunoglobulins. Different cells and proteins are a part of this system that helps the body against any infection. The immune system comprises of - 

a) White Blood Cells - White blood cells are the first barrier of the body against an infectious particle. They locate the foreign invader, be it bacteria, viruses, parasites or fungi, and attack them so that it doesn’t cause an infection. White blood cells are manufactured in the bone marrow.

b) Antibodies - Antibodies are immunoglobulins made up of proteins that neutralize the pathogens. Antibodies have the capability to recognize an antigen on the surface of the foreign particles and thus launch an attack against it to defend the body.

c) Lymphatic System - Lymphatic System runs throughout the body, looking for pathogens and cancerous cells and attacks them. The lymphatic system consists of Lymph nodes, lymph vessels, and white blood cells.

d) Spleen - Spleen filters the blood and removes microbes from the blood. It also destroys and filters the dead red blood cells in our body. The Spleen manufactures antibodies and lymphocytes.

e) Bone Marrow - Bone marrow is the center for the production of red blood cells, white blood cells, and platelets.

f) Thymus - Thymus also produces white blood cells and T-lymphocytes necessary components of the immune system.

6. Nervous System

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The nervous system is a complex system of nerves that carries impulses to and from the brain to different parts of the body. These impulses are coded messages that let the brain know what is going on and the brain, in turn, sends impulses that are responses to the stimulus.

The nervous system has three main functions to do.

i) Collect nerve impulses from the surrounding or within the body.

ii) Interpret the impulses.

iii) Give an appropriate response to the collected data.

The nervous system is made up of the nerve cells and fibers that carry the nerve impulses, the brain, and the spinal cord.

The brain and spinal cord form the central nervous system and the nerves and ganglia form the peripheral nervous system.

The Central Nervous System receives the information and coordinates the movements of different parts of the body, in response to the information received. The Central Nervous System or CNS controls the functions of the body and mind. Our brain is like the central processing unit, which processes all the information. All the sensory organs are connected to the brain and the brain receives signals from all of them. The spinal cord is the carrier of this information. It transports the information to the brain. The central nervous system controls voluntary movements like walking, talking, eating, etc. as well as involuntary actions like breathing, sneezing, blinking, etc.

The Peripheral Nervous System is a system that operates outside the brain and spinal cord. The nerves of the peripheral nervous system are connected to the sensory organs. Thus, it connects the CNS to the other parts of the body. The nerves of the Peripheral Nervous System are called Axons. The Peripheral Nervous System is further divided into 

a) Somatic Nervous which controls the voluntary movements of the body and 

b) Autonomic Nervous System which controls and regulates the involuntary movements of the body.

7. Reproductive System

Reproduction is the basis of continuity of life. It ensures the life and the race of the particular species goes on. The Reproductive system consists of the internal and external sex organs. It differs from male to female. The aim of reproduction is to produce offspring. Human beings can only reproduce by sexual reproduction. This kind of reproduction involves the mixing of genetic information and the production of gametes. Thus, it produces genetic variations. The reproductive system also consists of hormones, pheromones, and fluids, which are an integral part of the entire reproduction process. 

The Female Reproductive System consists of the ovaries. Every female has a pair of ovaries that produce eggs and female hormone- estrogen. The uterus or the womb is where fertilization takes place and the zygote is formed. Also, Uterus is the place where the embryo is planted and nurtured until birth. The Uterus is connected to the ovaries through fallopian tubes that carry the egg to the uterus for fertilization. 

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Male Reproductive System consists of the penis, scrotum, testes, epididymis, Vas deferens, Prostate glands, and seminal vesicles. Testes produce the sperms and store them and are covered by the protective covering of the scrotum. Vas deferens lie next to the scrotum. The sperms formed in the testes are mixed with various fluids from different glands including the prostate glands to keep it lubricated and protected.

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Sperms fuse into the egg to form a gamete which then turns into an embryo and implants itself in the uterus. The uterus takes care of the embryo and nourishes it into a healthy baby throughout the gestation period.

Thus, all the different systems in the human body work together and in coordination with each other to carry out all the life functions.

Structure of the Human Body & Parts

Humans are, without a doubt, the most complicated species on the planet. Although the human body is one structure, it is made up of billions of smaller structures that fall into four categories.

• Cells - Cells have long been considered as the most basic units of biological matter capable of sustaining life and reproduction.

• Tissues - Tissues are a little more complicated than cells. A tissue is defined as a collection of many comparable cells connected by various amounts and types of nonliving intercellular material.

• Organs - Organs are more sophisticated than tissues in terms of structure. An organ is a collection of various tissues that are structured in such a way that they may perform a certain function when combined.

• System - The most complicated of the human body's component units are systems. A system is a collection of organs of various sizes and types that are organized in such a way that they may execute complex functions for the body as a whole.

The physiological and psychological functions of bodily systems are referred to as body functions. The body's survival depends on its ability to maintain or restore homeostasis, or relative consistency, in its internal environment.

• Circulatory system- The circulatory system is a network of blood vessels and lymphatic vessels that runs throughout the body. It is the body's oxygen, hormone, and essential nutrition transport system, which is powered by the heart and helps it work properly.

• Respiratory system - To function, every tissue in the body requires oxygen. The respiratory system, which comprises the airways, pulmonary veins, lungs, and breathing muscles, delivers oxygenated blood to the body's tissues while also removing waste gasses.

• Digestive system - Through a chemical breakdown process, your digestive system allows your body to transform food into useful nutrients. This is accomplished by a tube-like organ system that includes the esophagus, stomach, liver, pancreas, and intestines.

• Skeletal system - The skeletal system serves as the body's foundation, giving structure, protection, and mobility. The body's 206 bones also generate blood cells, store critical minerals, and release vital hormones.

• Muscular system - The muscular system is made up of all of the muscles that move the skeleton, maintain posture by constant contraction, and create heat through cell metabolism.

• Nervous system - We can sense, comprehend, and respond to the environment around us thanks to the neurological system. The nervous system is also in charge of the body's basic physiologic operations including breathing and digestion.

As a result, all of the systems in the human body operate together  to carry out all of life's functions.