Organs of the body | Their Locations and Internal Functions

An organ is a structure that has a specific shape and function in the body. The human body has approximately 74 significant organs, either big or small, that form organ systems together.

List of Organs of the Body

1. Organs of Digestion: Esophagus, Stomach, liver, pancreas, small intestine, large intestine, rectum, anus, and mesentery.
2. Respiration organs: Lungs, nose, trachea, bronchi.
3. Urine Excretion: Kidneys, urinary bladder, urethra, ureters.
4. Blood Circulation: Heart, blood vessels, spleen.
5. The Nervous system: Brain and spinal cord.
6. Reproduction: Testis & penis in the male. Uterus, ovaries & mammary glands in the female.
7. Endocrine system: Pituitary gland, adrenal, thyroid, pancreas, parathyroid, prostate glands.
8. Sense organs: Skin, tongue, nose, eyes, ears.
9. Lymph and Immune system: Spleen, thymus, bone marrow, lymph nodes, lymph vessels.

Organs with locations and functions in detail

Each organ is made up of a group of tissues. Based on this, each organ has a specific set of tissues and a particular shape to suffice the body’s needs.

Digestive organs

These organs start from the mouth and end with the rectum. They are of different types, like

1. Tongue
2. Pharynx.
3. Esophagus
4. Stomach
5. Small intestine
6. Large intestine
7. Rectum

Tongue

The tongue is the organ located in the mouth.

The mouth is the entry point for food or other substances into the body. It has teeth, a tongue, and salivary glands.

The tongue has sensory buds that act as chemoreceptors to recognize the taste.

Besides, the tongue helps chew and moisten the food before being sent to the stomach through the esophagus.

Further, it is also essential for human speech.

Function:

1. Detect the taste and enhance the appetite.
2. It helps crushing the food into tiny pieces by moving them between teeth.
3. Makes a moist bolus for easy passage into the stomach.

Pharynx

It is a muscular tube-like structure that is present after the mouth.

It acts as a standard pass for food into the esophagus and air into the trachea.

The esophagus

This hollow organ has a tube-like structure connecting the mouth and stomach.

It helps in the passage of food from the mouth to the stomach.

It passes through the chest between the lungs.

Function:

• Passage of food balls into the stomach.
• May monitor the extent of moisture.

Stomach

It is one of the largest internal organs with a sack-like structure.

It is located in the belly portion and tilted towards the left of the central axis.

In an adult, it has a capacity of up to 2.5 liters to hold the food before it passes into the intestine.

The wall has foldings called rugae, which expand to accommodate more food.

Function:

1. Food consumed stays in the stomach for about an hour or two.
2. This food is sterilized by the hydrochloric acid from the gastric juice secreted by stomach walls.
3. Further, the enzyme amylase in gastric juice digests carbohydrates.
4. The stomach wall readily absorbs water, alcohol, and glucose.

Small intestine

This is a long tube-like structure, about 5 to 6 meters long.

It is a continuation of the stomach up to the Cecum and has three major parts like

1. Duodenum
2. Jejunum
3. Ileum

The food from the stomach enters the small intestine at the duodenum.

The duodenum is 25 cm long and receives bile juice and pancreatic juice secretions.

The jejunum is 3 meters long, and the ileum is 3 meters long.

Here, in the small intestine, there is a mixing of food with digestive juices, chemical digestion, and absorption of food.

The food stays here for approximately 8 hours before entering the large intestine.

Large intestine

This is an extension of the small intestine but has a greater diameter. It is 1.5 meters long and can be divided into

• Cecum
• ascending colon,
• transverse colon,
• descending colon,
• sigmoid colon and
• rectum.

This organ of the digestive system helps absorb water from undigested food stored in the bowel before being excreted as feces.

Further, it hosts many gut-friendly bacteria that synthesize Vitamin-K and help absorb vitamin B₁₂.

Mesentery

This recently discovered structure is considered a complete organ as it functions specifically and has a complete structure.

The mesentery helps to fix the intestinal structure of the abdominal walls like glue.

Accessory organs of digestion

These are the vital organs that aid in digestion. These consist of

1. Salivary glands
2. Liver
3. Pancreas.

Salivary glands

There are three pairs of salivary glands in the facial region. They secrete saliva into the mouth to keep it moist and help digest carbohydrates.

Liver

It is considered the biggest organ in the human anatomy. It weighs around 2 to 3 kg, making it the heaviest internal organ in a healthy adult.

It is on the right side of the body above the stomach, as seen in the image above.

It is an essential organ of metabolism and one of the principal organs in the human body that detoxifies substances.

It helps to convert any toxic substances or drugs into water-soluble inert materials. These are then readily excreted by the kidneys.

It is the organ where glucose is stored as glycogen and fat is converted to high-density and low-density lipoproteins.

It is also the place where bile is formed and released into the intestine for excretion. It is the most robust and active organ in the body. Damage to any portion of the liver is regenerated and repaired for efficient function.

Gall-bladder

It is a small organ below the liver. Here, the bile juice from the liver is concentrated before being released into the gut. See the image above for the location.

Pancreas

This organ located near the stomach acts as both an exocrine gland and an endocrine gland.

The exocrine gland secretes digestive enzymes like amylase, trypsin, and lipase, which digest carbohydrates, proteins, and fats. See the pancreatic enzymes for more details.

Meanwhile, the endocrine part secretes hormones like insulin and somatotropin, which regulate glucose levels in the blood.

Organs of Circulation

These include the heart and blood vessels like the arteries, veins, and capillaries.

Heart

This is the primary organ of the blood circulatory system. It is one of the organs on the left side of the body.

The heart’s function is to pump blood to reach the body’s deeper tissues.

It is the organ that functions non-stop from the time of its formation in the womb until an individual’s death.

It has veins carrying blood into it from the backside and arteries going out.

In an adult, it beats at an average of 60 to 100 beats per minute. It is made of cardiac muscles, part of the muscular system.

Arteries, Veins & Capillaries

These are duct-like organs that are connected to the heart. Arteries carry blood from the heart to all the tissues and cells of the body.

Veins bring impure blood from all the tissues and cells back to the heart. Capillaries are the finest ducts that emerge from arteries and converge again into veins.

They reach the cells, provide nutrition, and collect waste for expulsion by blood. There are few structural and functional differences between arteries and veins.

Organs of respiration

The list includes

• Nose
• Larynx
• Trachea
• Bronchi
• Lungs

Lungs

These are the principal organs of the respiratory system.

They take oxygen-rich air from the atmosphere into the body and expel carbon dioxide.

The oxygen from the air in the lungs is carried by blood circulating through the alveoli.

These lungs are sponge-like and can constrict and dilate. The average capacity is 4 liters of air.

Organs of the nervous system

Brain

This is the master organ of the body, as all the organ systems of the human body are under its control.

The skull, which is a bony frame of the head, houses the brain.

The brain is made up of nerve cells and neuroglia.

It consists of the cortex, cerebral hemisphere, cerebellum, medulla oblongata, and pons. It extends into the spinal cord.

For more details, refer to the article Parts of the brain.

Its essential functions include judgment, memory, reasoning, sleep, temperature control, body movements, reflex actions, etc. It exerts its action through neurotransmitters.

Spinal cord

This is the long cord located in the vertebral column.

It begins from the base of the brain and extends to hip bones into the sacrum.

The spinal cord gives out many nerves that pass through the entire body.

Along with the brain, it is a part of the nervous system.

Organs of the urinary system

Kidneys

These are the main organs involved in the excretion process.

There is a single pair of kidneys present on the dorsal side of the body in such a way that each kidney is located on either side of the vertebral column.

Kidneys are bean-shaped and brownish in color, with millions of nephrons inside.

These nephrons form an efficient filtration mechanism.

The waste from the blood is removed as it passes through millions of nephrons.

This filtrate waste is sent into the urinary bladder through the Ureter.

Ureters

These are the long ducts that connect the kidneys to the urinary bladder.

They carry the formed urine from nephrons to the bladder for expulsion.

Urinary bladder

This is a storage vesicle that stores urine brought from the kidneys by the ureters until voluntary urination.

Urethra

This tube-like extension originates from the urinary bladder and opens to the outside.

Sense Organs

These constitute five major organs that are part of different organ systems. These include

1. Skin
2. eyes
3. ears
4. nose
5. tongue

Skin

This is the largest organ of the body in terms of area. It belongs to the integumentary system.

It accounts for a few square meters in area. It covers the whole body, gives shape, and protects the inner tissues from germs.

It also acts as an organ of the sense of touch. The skin has sweat ducts, oil glands, and hair. In times of excess heat, the body expels sweat through the skin to reduce body temperature.

Sweat, sodium, chloride, and other waste are excreted from the body. This skin also acts as an organ of excretion.

Glands in the skin secrete an oily substance to prevent water loss and keep the surface smooth.

Eyes

The eyes are one of the 5 sense organs. They are the most vital organs that help with daily life activities.

They are a pair located in eye sockets in the skull on the front side of the head.

They are responsible for vision. The eyes are connected to the brain through optic nerves, which help in sight.

They work together with the ears for better balance, with the nose and tongue to enhance the appetite at the sight of food.

Ears

These are meant for hearing and body balance. They are a pair, each located on one side of the head.

The ears perform specific functions like the sense of hearing and the maintenance of body balance.

This way, they help in communication and safety.

Nose

This is an organ of respiration but also has the function of the sense of smell.

It has olfactory nerve endings in the nasal layers, which predict the scent.

It also has hair that catches dust entering the respiratory tract.

Tongue

This is the organ located in the mouth.

Endocrine glands

Pituitary gland

This gland is located in the brain but releases essential hormones that regulate body physiology.

Thyroid gland

This is an endocrine gland located near the neck region. It secretes thyroid hormones, which regulate metabolism and also body temperature.

Parathyroid gland

This is also the endocrine gland located along with the thyroid gland. They secrete parathormone, which regulates calcium levels in the blood.

Adrenal glands

This endocrine gland has two portions: the inner medulla, which secretes epinephrine, and the outer cortex, which secretes mineral and glucocorticoid hormones.

Epinephrine is the fight or flight hormone (emotion-related), while corticoids regulate body metabolism.

Pineal gland

This is a small reddish-brown colored gland present in the brain. It secretes the hormone melatonin, which regulates the circadian rhythm.

Refer for more details on glands in the body

Organs of the Lymphatic system

This includes organs like

Spleen

This organ is a part of the lymphatic system. It is located in the belly region near the intestines and stomach.

It is involved in the infiltration of blood and the destruction of old and worn-out red blood cells.

This also serves as a blood reservoir and even recovers iron from damaged RBC for reuse.

Thymus gland

An essential organ of the immune system, located near the sternum. This organ helps in the development of immune cells. It decreases in size as age progresses.

Lymph nodes

These are oval-shaped organs lying along the length of the lymph vessels. They help filtrate lymph, destroy cell debris, and increase T and B-lymphocytes.

Lymph vessels

These are the vessels that are found running beside the blood vessels. They carry the lymph away from tissues to mix into venous blood.

Reproductive system organs

The organs can be differentiated into male and female organs.

The male organs include

Testis

These are the external gland-like structures present in males near the groin. They have vas-differentia, which forms sperms.

Prostate gland

This gland secretes the prostate hormone. It is present in males and helps in the passage of sperm from the urethra.

Penis

This is the sexual organ present only in males.

Internally, it has a duct to carry the sperm and also consists of the urethra, which expels urine from the body.

The female organs include

Uterus

This organ is well-developed in the female reproductive system. It helps to host the fertilized zygote for nine months.

Here, the zygote grows into a baby. It provides all the required nutrients to the baby during the period.

Ovaries

These are present in women as extended portions of the uterus, as seen in the picture above.

They are a pair and help form ova, which can fertilize with sperm and form a baby.

Bone marrow

This is tissue, not an organ, inside the large bones. It exists as yellow and red bone marrow.

As a person ages, the red portion of it turns yellow. This bone marrow is essential in producing red blood cells, white blood cells, and even thrombocytes.

Interstitium

• This is a series of interconnected compartments of cells and the secretions in the body that are present around all the essential organs.

• They act as shock absorbers and help protect the organs from jerks and movements by the body.

• The interstitium is also responsible for the chemotaxis phenomenon, which occurs when white blood cells move to a specific region of injury.

Frequently Asked Questions and Answers

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Reference

1. Anatomy and Function of the Heart’s Electrical System
2. Principles of Anatomy and Physiology.
3. The mesentery: structure, function, and role in disease