Topic 2 : The anatomy and functions of important internal and external organs

Organs and body systems:

External organs can be seen easily, such as eyes, ears, nose, mouth, and skin. These organs have different functions.

Internal organs are located inside the body (Cannot been seen from the outside), and are extremely important, because these organs are the vital parts of the body’s system. The external and internal organs are required to function in sync with each other. If one of the organs is dysfunctional, other parts of the body will be affected which may cause the body’s system to fail.

External Organs

1. Eyes - are organs that enable humans to visualize the surroundings; they help to acquire knowledge visually. Without eyes, it is difficult for the brain to learn and memorize surroundings. Moreover, the eye’s movements contribute to several facial expressions, such as happiness, sadness, and surprise.

Anatomy of eyes

(1) Eyebrow is an area of thick, delicate hairs above the eyes. Their main function is to prevent sweat, water, dust, and other debris from falling down into the eyes.

(2) Eyelid is the muscle that retracts or elevates to allow light to enter the eye. It protects the eye from dust and other debris or whenever an object is coming to close to the eye.

(3) Eyelashes are hairs that grow at the edge of the eyelid which serves as extra protection for the eye from dust and other debris.

(4) Lachrymal glands are paired oral - shaped glands, one for each eye that secretes a liquid solution called tears to moisturize and rinse debris from the eyes. They are situated in the upper, outer portion of each orbit.

2. Ears - are organs that detect sounds such as music, and conversation. Hearing is a form of communication between people. If the ears do not function properly, a person may hear little or no sound. The brain cannot process any incoming sound into useful information.

Anatomy of the ear

The ear has 3 anatomical parts: outer, middle, and inner ear.

(1) Components of the outer ear as follow:

Pinna serves as a collector of sound vibrations, and guides the vibrations down the ear canal.

Ear canal acts as a passage for sound waves to travel though the skull to the eardrum. Deep down the ear canal, there are cerumen glands (wax glands) that produce an oily substance that acts as a moisturizer. Also this substance can trap dust and other debris that are falling into the canal, forming earwax. At the end of the canal there is the head of the eardrum membrane, separating the outer and middle ear, which transfers the vibrations to the middle ear.

(2) Middle ear is a canal containing three tiny bones, called ossicles: the malleus (hammer), the incus (anvil), and the stapes (stirrup). These bones mechanically convert the vibration from the eardrum caused by the sound waves into pressure waves transmitted to the inner ear.

(3) Inner ear contains the cochlea which is shaped like a snail. The cochlea converts the pressure waves in its fluid which come from the middle ear into nerve impulses. The brain than can process these impulses into sound information.

3. Nose - is the organ responsible for smelling and breathing. If the nose does not function properly, the individual cannot sense any smell and has difficulties in breathing, which can alter their voice.

Anatomy of the nose

The nose is an external organ, which is situated in the middle of the face. It contributes to the appearance of a facial feature. A nose can be divided into 3 components:

(1) Bridge of the nose can be seen from the outside, which is a soft bone. Its function is to protect the interior parts of the nose.

(2) Nostrils are the two channels of the nose, serving as passages for the air during inhaling and exhaling. There are hairs growing along the channel, filtering dust, some microorganisms and other debris from entering the windpipe and the lungs.

(3) Para nasal Sinuses are a group of four paired air-filled spaces that surround the nasal cavity in the skull. Their biological functions are to drive the inhaled air into the lungs and regulate the humidity and temperature of inhaled air.

4. Mouth and teeth are essential organs to establish oral communication, produce vocal sounds, and consume foods. Humans have only 2 sets of teeth: primary (falling off at maturity) teeth and permanent teeth.

1) Deciduous teeth are the first set of teeth where ten are found in the upper jaw and ten in the lower jaw, for a total of 20. The primary teeth start to appear at about six to eight months of age and are fully grown at the age of two to two and a half years. The process of losing the primary teeth begins at the age of 6 years.

2) Permanent teeth are the second set of teeth, which are the replacement of the primary teeth. Among the permanent teeth, 16 are found in the upper jaw and 16 in lower jaw, for a total of 32. This set of teeth will be fully-grown at the age of 21 to 25 years; there is no replacement if a permanent tooth decays or falls out.

Functions of the teeth

Teeth are used to break down food by cutting and shredding them into small pieces. The teeth have many functions and shapes. There is the incisor which has a shape of a wedge; it’s primarily used for cutting the food into a reasonable size, the canines are used for tearing food apart, while molars are used for grinding food.

5. Skin is the soft outer tissue, covering of the entire body that can sense a variety of physical conditions such as hot and cold, touch, and pain. It is the first line of defense against the external environment. It regulates the body’s temperature through sweating which is produced by glands under the skin.

Skin is composed of twoprimary layers:

1. Epidermis is the outermost layer of skin, which provides protections against pathogens. Its lower layers will migrate toward the surface and build the outer layer which will be shed at the surface. Those layers that already migrated toward the surface will be replaced by new cell membranes.

2. Dermis is the layer of skin underneath the epidermis. It is thicker than the epidermis. Due to its thickness, the dermis provides tensile strength and elasticity to the skin. It contains the sweat glands, sebaceous glands, apocrine glands, and many nerve cells.

Internal Organs

Internal organs are found beneath the skin and can’t be seen. The internal organs consist of many components and their functions perform in conjunction with one another as a system.

1. Lungs are one of the internal organs that control the respiration process. The lungs are located on either side of the chest, above the diaphragm. The inhaled air is conducted through trachea, and gets distributed into both lungs through small tubular branches called bronchi. The lungs are a soft and sponge like tissue and can be inflated up against the ribs. Covering the lungs is a thin tissue called the pleura. At each end of the tubular branches are many thousands of tiny air sacs, called alveoli where the exchange of oxygen and carbon dioxide takes places. They inflate and contract with the airflow. The alveoli are connected to tiny nerve cells that contain capillaries. The blood flows through these capillaries and exchanges oxygen and carbon dioxide. The oxygen will be used in chemical reactions, called metabolism, that break down food. This process of gas exchange is called dialysis.

Functions of the lungs

Their principal function is to control respiration and purify the blood through gas exchange. Breathing involves the act of inhaling and exhaling. Inhaling occurs as the diaphragm contracts (moves down), the chest cavity expands which causes the lungs to expand; conversely, exhaling occurs when the diaphragm relaxes (moves up), the chest cavity contracts, causing the lungs to shrink. The diaphragm is located under the lungs, separating chest cavity and tummy. Adults will breathe 18 -22 times per minute, while youth’s respiration rate will be higher due to their age.

Heart is a muscular, hollow organ that has the shape of a lotus and the size of a fist. A layered membrane is covering the heart. A yellow fluid separates the two layers of membrane, preventing friction between the two layers as the heart beats and lubricating the heart so that it does not stick on to the membrane. The heart is located between the lungs in the middle of the chest, behind and slightly to the left of the breastbone. The tip of the heat points slanting downward and to the left. Inside the heart are 4 chambers, separated by muscular walls: the two upper chambers and two lower chambers. The upper chambers are slightly smaller than the lower chambers.

Functions of the heart

The heart has a compression stroke, so called heart beat which pumps the red blood to the organs, tissues, and cells of the body. Relaxation of the upper chambers will receive the incoming blood from every part of the body. It is pushed through a valve to the bottom right chamber and then pumped straight to the lungs for the respiration process. After the gas exchange, the oxygen-rich blood will be pumped back to the upper left chamber of the heart and is then send through a valve to the bottom left chamber, before being pumped back into the body. If an artery is touched, the heart’s beating can be felt and is called the pulse.

The heart is the most important organ, because it indicates whether a person is still alive or not. If the heart stops beating, a person is pronounced dead. The pulse rate of a normal person is 70 - 80 beats per minute.

The heart will beat continuously throughout the lifespan, whether falling asleep or being awake. The heart will relax when fallen asleep; the pulse rate is slightly lower than normal. It is very important to maintain good health by avoiding stressing out the heart.

Stomach has the shape of calabash, similar to a pig’s stomach, and has a capacity of 1 liter. It is connected to the gullet (also known as the esophagus) and located on the left side of the upper abdomen.

Importance of stomach

The stomach’s importance is to digest food after chewing into nutrients before passing it to the small intestine. The small intestines will absorb nutrients that are essential for the maintenance of life and growth. While the non-nutrient substances, called fiber will be passed on to the large intestine, in order to be processed into feces. The stomach secretes a strong acid, called gastric acid to aid in food digestion; the gastric acid is secreted in a large volume when consuming food. If a person does not consume food at the right time, he or she may experience stomach pain caused by open sores that are created by the erosion of the stomach wall (peptic ulcers). To prevent the erosion, drinking clean water, consuming meals at the right time, and avoiding spicy foods are recommended.

Small intestine is a long tubular structure, located in the upper tummy. It has an average length of 6 meters. The upper end is connected to the stomach and lower end is connected to the large intestine.

Functions of the small intestine

are to continue digesting food and break it down, so that the nutrients can be extracted and absorbed into the blood vessels, which then get distributed to different parts of the body.

Large intestine is a part of gastrointestinal tract. The average length of the large intestine is 1.5 meters and the diameter is 6 centimeters. It consists of 3 parts:

(1) Cecum is the first section of the large intestine, connected to small intestine; it receives fecal material from the small intestine.

(2) Colon is the longest section of the large intestine, consisting of the ascending colon, the transverse colon, and descending colon. It absorbs water, vitamin B12 compounds which bacteria inside the colon synthesize, and passes fibers and waste to the next part of the large intestine.

(3) Rectum is the final straight portion of the large intestine. When the rectum becomes full of waste, a person will feel the need to defecate, because the increase in interracial pressure forces the wall of the anal canal apart and the rectum shortens as feces are propelled out of the anus.

Functions of the large intestine

1) Help to digest the remaining food.

2) Defecation.

3) Absorb water and ions such as sodium, other minerals from the remaining digested food, and vitamin compounds that are synthesized by bacteria inside the large intestine, such as vitamin B complex, vitamin K. Therefore, water, food, and medicines can be fed via the anus for certain patients, since the large intestine can absorb certain vitamins and minerals essential to the body.

4) Store the feces until it is full and ready to defecate.

The kidneys Kidney is an organ that is essential to the urinary system; it excretes waste in the form of urine. The two kidneys have a bean-shaped structure; each kidney is approximately 12 centimeters long.

The kidneys are located at the back of abdominal cavity, and slightly below the ribs.filter the blood and remove waste from it which is diverted to the urinary bladder and then disposed by urination.

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