Immune System
Adenoids - Adenoids are a patch of tissue that is high up in the throat, just behind the nose. They, along with the
tonsils, are part of the lymphatic system. The lymphatic system clears away infection and keeps body fluids in
balance. The adenoids and tonsils work by trapping bacteria or viruses coming in through the mouth and nose.
Adenoids do important work as infection fighters for babies and young children. But they become less important as
a child gets older and the body develops other ways to fight germs. In kids, adenoids usually begin to shrink after
about 5 years of age.
Bone Marrow - Blood cells are made inside the spongy tissue in our bones, called bone marrow. The process of blood
cell formation is called haematopoiesis. Blood cells start off as stem cells, which are young cells that grow into
mature blood cells. Healthy people have enough stem cells to keep on producing new blood cells, continuously. Blood
flows through the marrow to pick up fully formed platelets, red cells and white cells to circulate to the rest of the
body.
Lymph Nodes - Lymph nodes (or lymph glands) are small lumps of tissue that contain white blood cells, which fight
infection. They are part of the body’s immune system and filter lymph fluid, which is composed of fluid and waste
products from body tissues. They help fight infections, and also play an important role in cancer diagnosis,
treatment and the chance of recovery or recurrence. Lymph nodes are located throughout the body, including the
neck, armpits, groin, around the gut, and between the lungs. Lymph nodes drain lymph fluid from nearby organs or
areas of the body. Lymph fluid is carried to the lymph nodes by lymphatic vessels. The lymph nodes filter out
harmful substances and waste products. They also contain immune cells called lymphocytes that destroy cancer
cells and bacteria. The filtered fluid is then returned to the blood circulation.
Mucous Membranes - The moist, inner lining of some organs and body cavities. Glands in the mucous membrane
make mucus (a thick, slippery fluid). Also called mucosa. The mouth, tongue, esophagus, stomach, and intestines are
all lined with mucous membranes. These membranes are referred to as the oral mucosa, esophageal mucosa, gastric
mucosa, and intestinal mucosa. Some mucous membranes secrete mucus, a thick protective fluid. The function of the
membrane is to stop pathogens and dirt from entering the body and to prevent bodily tissues from becoming
dehydrated.
Skin - The skin is an organ harboring several types of immune cells that participate in innate and adaptive immune
responses. The immune system of the skin comprises both skin cells and professional immune cells that together
constitute what is designated skin-associated lymphoid tissue. The skin is an archetype of organs involved in
mechanical and immunological barriers to pathogens and in body homeostasis. Tissues that form host–environment
interfaces, including mucosal surfaces, represent the primary stage of defense against pathogenic microorganisms. .
The skin comprises the epidermis, dermis, cutaneous appendages, and subcutaneous tissue.
Peyer’s Patches - Peyer’s patches are groupings of lymphoid follicles in the mucus membrane that lines your small
intestine, most in your ileum. Lymphoid follicles are small organs in your lymphatic system that are similar to lymph
nodes. Peyer’s patches play an important role in immune surveillance of materials within your digestive system.
Immune surveillance refers to the process by which your immune system recognizes and destroys potential
pathogens.Peyer’s patches contain a variety of immune cells, including macrophages, dendritic cells, T cells, and B
cells. There are also specialized cells, called M cells, next to your Peyer’s patches. These M cells feed antigens to the
macrophages and dendritic cells of your Peyer’s patches. An antigen is a substance, such as a virus, that might
produce a response from your immune system. The macrophages and dendritic cells then show these antigens to
your T cells and B cells, which determine whether or not the antigen requires an immune response. If they
recognize the antigen as a harmful pathogen, the T cells and B cells in your Peyer’s patches signal your immune
system to attack it. Sometimes, bacteria and viruses can hack this mechanism and use it to enter the rest of your
body through your small intestine.
Spleen - The spleen is a small organ inside your left rib cage, just above the stomach. It’s part of the lymphatic
system (which is part of the immune system). The spleen stores and filters blood and makes white blood cells that
protect you from infection. Many diseases and conditions can affect how the spleen works. A ruptured (torn) spleen
can be fatal. Your spleen is a small organ that sits inside your left rib cage, just above your stomach. In adults, the
spleen is about the size of an avocado. The spleen is part of your lymphatic system (which is part of your immune
system). It does several important jobs to keep your body healthy.
Thymus - Your thymus is a small gland in the lymphatic system that makes and trains special white blood cells
called T-cells. The T-cells help your immune system fight disease and infection. Your thymus gland produces most of
your T-cells before birth. The rest are made in childhood and you’ll have all the T-cells you need for life by the time
you hit puberty. The thymus is a small gland that’s part of your lymphatic system. Your lymphatic system is made
up of a network of tissues, vessels and organs such as your tonsils, spleen and appendix. Your lymphatic system is
part of your immune system. It helps defend against infection and disease.
Tonsils - The two palatine tonsils are found on the right and left of the back of the throat, and are the only tonsils
that can be seen unaided when you open your mouth. The adenoids are found high up in the throat, behind the
nose, and can only be seen through rhinoscopy (an examination of the inside of the nose). The lingual tonsil is
located far back at the base of the tongue, on its back surface.
White Blood Cells. The tonsils are part of the body’s immune system. Because of their location at the throat and
palate, they can stop germs entering the body through the mouth or the nose. The tonsils also contain a lot of
white blood cells, which are responsible for killing germs.
Digestive System
Mouth - Food starts to move through your GI tract when you eat. When you swallow, your tongue pushes the food
into your throat. A small flap of tissue, called the epiglottis, folds over your windpipe to prevent choking and the
food passes into your esophagus.
Esophagus - The esophagus is a muscular tube that connects the pharynx (throat) to the stomach. The esophagus
contracts as it moves food into the stomach. A “valve” called the lower esophageal sphincter (LES) is located just
before the opening to the stomach. This valve opens to let food pass into the stomach from the esophagus and it
prevents food from moving back up into the esophagus from the stomach.
Stomach - The stomach is a J-shaped organ that digests food. It produces enzymes (substances that create
chemical reactions) and acids (digestive juices). This mix of enzymes and digestive juices breaks down food so it can
pass to your small intestine. Your stomach’s purpose is to digest food and send it to your small intestine. It has
three functions: Temporarily store food, contract and relax to mix and break down food, and to
produce enzymes and other specialized cells to digest food. The size of the stomach varies from person to person.
Your stomach expands when full and deflates when empty. Because of this, your stomach size can vary depending on
how recently and how much you have eaten.
Small Intestine - The small intestine is a long tube-like organ that connects the stomach and the large intestine.
It is about 20 feet long and folds many times to fit inside the abdomen. The small intestine has three parts: the
duodenum, jejunum, and ileum. It helps to further digest food coming from the stomach. It absorbs nutrients
(vitamins, minerals, carbohydrates, fats, proteins) and water from food so they can be used by the body. The small
intestine is part of the digestive system. The small intestine connects the stomach and the colon. It includes the
duodenum, jejunum, and ileum.
Large Intestine - The long, tube-like organ that is connected to the small intestine at one end and the anus at the
other. The large intestine has four parts: cecum, colon, rectum, and anal canal. Partly digested food moves through
the cecum into the colon, where water and some nutrients and electrolytes are removed. The remaining material,
solid waste called stool, moves through the colon, is stored in the rectum, and leaves the body through the anal
canal and anus. The esophagus and stomach are part of the upper gastrointestinal (digestive) system.
Colon - The colon is responsible for processing waste so that emptying your bowels is easy and convenient. It’s a
6-foot long muscular tube that connects the small intestine to the rectum. The colon is made up of the cecum, the
ascending (right) colon, the transverse (across) colon, the descending (left) colon, and the sigmoid colon, which
connects to the rectum. Stool, or waste left over from the digestive process, is passed through the colon by means of
peristalsis, first in a liquid state and ultimately in a solid form. As stool passes through the colon, water is removed.
Stool is stored in the sigmoid (S-shaped) colon until a "mass movement" empties it into the rectum once or twice a
day. It normally takes about 36 hours for stool to get through the colon. The stool itself is mostly food debris and
bacteria. These “good” bacteria perform several useful functions, such as synthesizing various vitamins, processing
waste products and food particles and protecting against harmful bacteria. When the descending colon becomes full
of stool, or feces, it empties its contents into the rectum to begin the process of elimination (a bowel movement).
Rectum - The rectum is a straight, 8-inch chamber that connects the colon to the anus. The rectum's job is to
receive stool from the colon, let you know that there is stool to be evacuated (pooped out) and to hold the stool until
evacuation happens. Muscles in the wall of your colon separate waste into small segments that are pushed into your
lower colon and rectum. As the rectal walls are stretched, they signal the need for a bowel movement. When the
sphincter muscles in your anus relax, the rectal walls contract to increase pressure.
Liver - The liver has many functions, but its main job within the digestive system is to process the nutrients
absorbed from the small intestine. Bile from the liver secreted into the small intestine also plays an important role
in digesting fat and some vitamins. The liver is your body's chemical "factory." It takes the raw materials absorbed
by the intestine and makes all the various chemicals your body needs to function. The liver also detoxifies potentially
harmful chemicals. It breaks down and secretes many drugs that can be toxic to your body.
Gallbladder - The gallbladder is a sac located under the liver. It stores and concentrates bile produced in the liver.
Bile aids in the digestion of fat and is released from the gallbladder into the upper small intestine in response to
food (especially fats). Your gallbladder is a small, pear-shaped organ in your upper right abdomen. Your gallbladder
stores and releases bile to help your digestive system break down fats. The most common issue you may develop with
your gallbladder is gallstones. Gallstones are pebble-like objects made from bile material.
Pancreas - The pancreas secretes digestive enzymes into the duodenum that break down protein, fats and
carbohydrates. The pancreas also makes insulin, passing it directly into the bloodstream. Insulin is the chief
hormone in your body for metabolizing sugar.
Salivary Glands - Salivary glands make saliva, which aids in digestion, keeps your mouth moist and supports healthy
teeth. You have three pairs of major salivary glands under and behind your jaw: parotid, sublingual and
submandibular. The parotid glands are the largest salivary glands. They are located just in front of the ears. The
saliva produced in these glands is secreted into the mouth from a duct near your upper second molar. Each parotid
gland has two parts, or lobes: the superficial lobe and the deep lobe. Between the two lobes is the facial nerve. The
facial nerve is important because it controls your ability to close your eyes, raise your eyebrows, and smile. Other
critical structures near the parotid glands include the external carotid artery, which is a major supplier of blood to
the head and neck region, and the retromandibular vein, a branch of the jugular vein.
Respiratory system
Nose - Nose, the prominent structure between the eyes that serves as the entrance to the respiratory tract and
contains the olfactory organ. It provides air for respiration, serves the sense of smell, conditions the air by
filtering, warming, and moistening it, and cleans itself of foreign debris extracted from inhalations.
Nasal Cavity - The nose has two cavities, separated from one another by a wall of cartilage called the septum. The
external openings are known as nares or nostrils. The roof of the mouth and the floor of the nose are formed by
the palatine bone, the mouth part of which is commonly called the hard palate; a flap of tissue, the soft palate,
extends back into the nasopharynx, the nasal portion of the throat, and during swallowing is pressed upward, thus
closing off the nasopharynx so that food is not lodged in the back of the nose.
Sinuses - The sinuses are cavities, or air-filled spaces, near the nasal passage. Like the nasal passage, the sinuses
are lined with mucous membranes. There are four different types of sinuses ; Ethmoid sinus. Located inside the
face, around the area of the bridge of the nose. This sinus is present at birth, and continues to grow. Maxillary
sinus. Located inside the face, around the area of the cheeks. This sinus is also present at birth, and continues to
grow. Frontal sinus. Located inside the face, in the area of the forehead. This sinus does not develop until around 7
years of age. Sphenoid sinus. Located deep in the face, behind the nose. This sinus does not develop until
adolescence.
Pharynx - The hollow tube inside the neck that starts behind the nose and ends at the top of the trachea
(windpipe) and esophagus (the tube that goes to the stomach). The pharynx is about 5 inches long, depending on
body size. Also called throat. The three parts of the pharynx are the nasopharynx, oropharynx, and hypopharynx.
Larynx - Your larynx is a hollow tube that connects your throat (pharynx) to the rest of your respiratory system.
It helps you swallow safely and contains the vocal cords, so it’s often called the voice box. Certain conditions and
behaviors can damage your larynx and your voice, but some strategies and specialists can help. Your larynx is inside
the middle of your neck, at the level of the Adam’s apple. It’s located between your fourth to sixth cervical
vertebrae.
Epiglottis - The flap that covers the trachea during swallowing so that food does not enter the lungs. Anatomy of
the larynx. The three parts of the larynx are the supraglottis (including the epiglottis), the glottis (including the
vocal cords), and the subglottis.
Trachea - The trachea is the long tube that connects your larynx (voice box) to your bronchi. Your bronchi sends
air to your lungs. Your trachea is a key part of your respiratory system. The trachea is made of rings of cartilage.
It is lined with cells that produce mucus. This mucus keeps allergens, dust particles or other debris out of your lungs.
When you breathe in, air travels from your nose or mouth through your larynx. It then passes through your
trachea to your bronchi. Your bronchi carries the air to your lungs. Your trachea is part of your tracheobronchial
tree. The tracheobronchial tree is where air travels to your lungs and exchanges gases (carbon dioxide and oxygen).
Diaphragm - The diaphragm, located below the lungs, is the major muscle of respiration. It is a large, dome-shaped
muscle that contracts rhythmically and continually, and most of the time, involuntarily. Upon inhalation, the
diaphragm contracts and flattens and the chest cavity enlarges. This contraction creates a vacuum, which pulls air
into the lungs. Upon exhalation, the diaphragm relaxes and returns to its dome-like shape, and air is forced out of
the lungs.
Lungs - All day, every day, your lungs work, often without you thinking about it. On this page, we explain what your
lungs are made of, how they work and the muscles you use to breathe. How often you breathe in and out every
minute depends on your age and what you’re doing. If you’re resting, an adult will breathe around 12-20 times a
minute – that adds up to around 17,000 – 30,000 times a day! The amount of air that moves in and out of your
lungs can vary from just a few litres a minute when you’re resting, to over 100 litres a minute if you’re exercising
vigorously. The lungs absorb oxygen from the air you breathe in and transfer it into your bloodstream so that it
can get to every part of your body. As the cells in your body work, they produce a waste gas called carbon dioxide
that is released into the bloodstream. Your lungs get rid of this waste gas when you breathe out. Your two lungs fill
your chest and sit on either side of your heart. Lungs are made up of areas called lobes – your right lung has three
lobes, and your left lung has two. Your left lung is smaller than your right because it shares that side of the chest
with your heart.
Bronchi Bronchial Tubes Bronchioles Air Sacs Capillaries -
Alveoli Lung Lobes Pleura Cilia -
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