The immune system – Functions, definition, anatomy, organs

Our bodies have enemies, which we are unable to see and may not even be aware to exist. We also have an army that expertly protects us against all forms of external threat and is constantly on guard: our “immune system!”

The immune system, which is made up of special cells, proteins, tissues, and organs, defends people against germs and microorganisms every day.

The human body features: immune system

The immune system is a network of cells, tissues, and organs that work together to defend the body against attacks by “foreign” invaders.

Organs of immune system: tonsils and adenoids, lymph nodes, lymphatic vessels, thymus, spleen, appendix and bone marrow.

Bone marrow, the soft tissue in the hollow center of bones, is the ultimate source of all blood cells, including lymphocytes. The thymus is a lymphoid organ that lies behind the breastbone.

Lymph nodes, which are located in many parts of the body, are lymphoid tissues that contain numerous specialized structures: T cells from the thymus concentrate in the paracortex; B cells develop in and around the germinal centers; Plasma cells occur in the medulla.

The Male reproductive system – Functions, definition, anatomy, disease

The human male reproductive system consists of a number of sex organs that are a part of the human reproductive process. In the case of men, these sex organs are located outside a man’s body, around the pelvic region.

The main male sex organs are the penis and the testes which produce semen and sperm, which as part of sexual intercourse fertilize an ovum in a woman’s body and the fertilized ovum (zygote) gradually develops into a fetus, which is later born as a child.

The human body Male Reproductive system

In the human reproductive process, two kinds of sex cells, or gametes, are involved. The male gamete, or sperm, and the female gamete, the egg or ovum, meet in the female’s reproductive system to create a new individual. Both the female and male reproductive systems are essential for reproduction.

The penis has a long shaft and enlarged tip called the glans penis. The penis is the male copulatory organ. When the male becomes sexually aroused, the penis becomes erect and ready for sexual intercourse. Erection is achieved because blood sinuses within the erectile tissue of the penis become filled with blood. The arteries of the penis are dilated while the veins are passively compressed so that blood flows into the erectile cartilage under pressure. The male penis is made of two different tissues. Cartilage is not in the penis.

Both the male and female reproductive systems play a role in pregnancy. Problems with these systems can affect fertility and the ability to have children. There are many such problems in men and women. Reproductive health problems can also be harmful to overall health and impair a person’s ability to enjoy a sexual relationship.

Your reproductive health is influenced by many factors. These include your age, lifestyle, habits, genetics, use of medicines and exposure to chemicals in the environment. Many problems of the reproductive system can be corrected.

Penis Diseases: Problems with the penis can cause pain and affect a man’s sexual function and fertility. Penis disorders include;

  • Erectile dysfunction – inability to get or keep an erection
  • Priapism – a painful erection that does not go away
  • Peyronie’s disease – bending of the penis during an erection due to a hard lump called a plaque
  • Balanitis – inflammation of the skin covering the head of the penis, most often in men and boys who have not been circumcised
  • Penile cancer – a rare form of cancer, highly curable when caught early

Testicular Disorders: Testicles, or testes, make male hormones and sperm. They are two egg-shaped organs inside the scrotum, the loose sac of skin behind the penis. Testes are suspended outside the abdominal cavity by the scrotum, a pouch of skin that keeps the testes close or far from the body at an optimal temperature for sperm development. It’s easy to injure your testicles because they are not protected by bones or muscles. Men and boys should wear athletic supporters when they play sports.

You should examine your testicles monthly and seek medical attention for lumps, redness, pain or other changes. Testicles can get inflamed or infected. They can also develop cancer. Testicular cancer is rare and highly treatable. It usually happens between the ages of 15 and 40.

The female reproductive system – Functions, definition, anatomy, disease

In the human reproductive process, two kinds of sex cells, or gametes, are involved. The male gamete, or sperm, and the female gamete, the egg or ovum, meet in the female’s reproductive system to create a new individual. Both the male and female reproductive systems are essential for reproduction. The female needs a male to fertilize her egg, even though it is she who carries offspring through pregnancy and childbirth.

The human body features

Both the male and female reproductive systems play a role in pregnancy. Problems with these systems can affect fertility and the ability to have children. There are many such problems in men and women. Reproductive health problems can also be harmful to overall health and impair a person’s ability to enjoy a sexual relationship.

Your reproductive health is influenced by many factors. These include your age, lifestyle, habits, genetics, use of medicines and exposure to chemicals in the environment. Many problems of the reproductive system can be corrected.

The female reproductive system contains two main parts: the uterus, which hosts the developing fetus, produces vaginal and uterine secretions, and passes the male’s sperm through to the fallopian tubes; and the ovaries, which produce the female’s egg cells. These parts are internal; the vagina meets the external organs at the vulva, which includes the labia, clitoris and urethra. The vagina is attached to the uterus through the cervix, while the uterus is attached to the ovaries via the Fallopian tubes. At certain intervals, the ovaries release an ovum, which passes through the Fallopian tube into the uterus.

If, in this transit, it meets with sperm, the sperm penetrate and merge with the egg, fertilizing it. The fertilization usually occurs in the oviducts, but can happen in the uterus itself. The zygote then implants itself in the wall of the uterus, where it begins the processes of embryogenesis and morphogenesis. When developed enough to survive outside the womb, the cervix dilates and contractions of the uterus propel the fetus through the birth canal, which is the vagina.

The ova are larger than sperm and are generally all created by birth. Approximately every month, a process of oogenesis matures one ovum to be sent down the Fallopian tube attached to its ovary in anticipation of fertilization. If not fertilized, this egg is flushed out of the system through menstruation.

Organs of the female reproductive system: A female’s internal reproductive organs are the vagina, uterus, fallopian tubes, and ovaries.

The vagina is the place where semen from the male is deposited into the female’s body at the climax of sexual intercourse, commonly known as ejaculation. Around the vagina, pubic hair protects the vagina from infection and is a sign of puberty. The cervix is the lower, narrow portion of the uterus where it joins with the top end of the vagina. The uterus is the major female reproductive organ of humans. One end, the cervix, opens into the vagina; the other is connected on both sides to the fallopian tubes. The uterus is a pear-shaped muscular organ. Its major function is to accept a fertilized ovum which becomes implanted into the endometrium, and derives nourishment from blood vessels which develop exclusively for this purpose. The fertilized ovum becomes an embryo, develops into a fetus and gestates until childbirth. If the egg does not embed in the wall of the uterus, a woman gets her period and the egg is flushed away. The Fallopian tubes are two very fine tubes leading from the ovaries of female into the uterus. The ovaries are the place inside the female body where ova or eggs are produced.

Diseases and Disorders of the Female Reproductive System: Vulvovaginitis, Nonmenstrual vaginal bleeding, Ectopic Pregnancy, Ovarian tumors, Ovarian cysts, Polycystic ovary syndrome, Trichomonas vaginalis, Dysmenorrhea, Menorrhagia, Oligomenorrhea, Amenorrhea, Toxic shock syndrome, Candidasis, Cervical cancer, Ovarian cancer, Uterine cancer, Breast cancer.

The Digestive system – Functions, location, definition, organs, disease

The digestive system is one of the most complex systems of the body. The digestive system is made up of organs that break down food into vitamins, minerals, protein, carbohydrates, and fats, which the body needs for energy, growth, and repair.

The main organs of the digestive system are mouth, esophagus, stomach, small and large intestines, anus, appendix. Accessory organs to the alimentary canal include the liver, gallbladder, and pancreas.

The human digestive system

When you eat foods-such as bread, meat, and vegetables-they are not in a form that the body can use as nourishment. Food and drink must be changed into smaller molecules of nutrients before they can be absorbed into the blood and carried to cells throughout the body. Digestion is the process by which food and drink are broken down into their smallest parts so the body can use them to build and nourish cells and to provide energy.

Digestion involves mixing food with digestive juices, moving it through the digestive tract, and breaking down large molecules of food into smaller molecules. Digestion begins in the mouth, when you chew and swallow, and is completed in the small intestine.

In human body, food enters the mouth, being chewed by teeth, and broken down by the saliva from the salivary glands. Then it travels down the esophagus into the stomach, where acid begins physical break down of some food, and chemical alteration of some. The “leftovers” go through the small intestine, through the large intestine, and are excreted during defecation.

The circulatory system – Functions, definition, anatomy, organs, diseases

The circulatory system is an organ system that passes nutrients (such as amino acids and electrolytes), gases, hormones, blood cells, nitrogen waste products, etc. to and from cells in the body to help fight diseases and help stabilize body temperature and pH to maintain homeostasis. This system may be seen strictly as a blood distribution network, but some consider the circulatory system as composed of the cardiovascular system, which distributes blood, and the lymphatic system, which distributes lymph.

The human body circulatory system

On average, your body has about 5 liters of blood continually traveling through it by way of the circulatory system. The heart, the lungs, and the blood vessels work together to form the circle part of the circulatory system. The pumping of the heart forces the blood on its journey.

Two types of fluids move through the circulatory system: blood and lymph. The blood, heart, and blood vessels form the cardiovascular system. The lymph, lymph nodes, and lymph vessels form the lymphatic system. The cardiovascular system and the lymphatic system collectively make up the circulatory system.

The circulatory system is divided into three major parts: heart, blood and blood vessels.

Cardiovascular disease is a class of diseases that involve the heart or blood vessels (arteries and veins). Cardiovascular disease refers to any disease that affects the cardiovascular system, principally cardiac disease, vascular diseases of the brain and kidney, and peripheral arterial disease. The causes of cardiovascular disease are diverse but atherosclerosis and/or hypertension are the most common.

The Human Veins – Functions, location, disease, heart, circulatory system, blood

In the circulatory system, veins are blood vessels that carry blood toward the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood. They differ from arteries in structure and function; for example, arteries are more muscular than veins and they carry blood away from the heart.

The human body veins

Veins serve to return blood from organs to the heart. In systemic circulation oxygenated blood is pumped by the left ventricle through the arteries to the muscles and organs of the body, where its nutrients and gases are exchanged at capillaries, entering the veins filled with cellular waste and carbon dioxide. The de-oxygenated blood is taken by veins to the right atrium of the heart, which transfers the blood to the right ventricle, where it is then pumped through the pulmonary arteries to the lungs. In pulmonary circulation the pulmonary veins return oxygenated blood from the lungs to the left atrium, which empties into the left ventricle, completing the cycle of blood circulation.

Veins are classified in a number of ways, including superficial vs. deep, pulmonary vs. systemic, and large vs. small.

Superficial veins are those whose course is close to the surface of the body, and have no corresponding arteries. Deep veins are deeper in the body and have corresponding arteries. The pulmonary veins are a set of veins that deliver oxygenated blood from the lungs to the heart. Systemic veins drain the tissues of the body and deliver deoxygenated blood to the heart.

The Human Thyroid – Functions, location, definition, anatomy, disease

The thyroid is one of the largest endocrine glands in the body. This gland is found in the neck inferior to (below) the thyroid cartilage (also known as the Adam’s apple in men) and at approximately the same level as the cricoid cartilage. The thyroid controls how quickly the body burns energy, makes proteins, and controls how sensitive the body should be to other hormones.

The human body human thyroid

The thyroid participates in these processes by producing thyroid hormones, principally thyroxine (T4) and triiodothyronine (T3). These hormones regulate the rate of metabolism and affect the growth and rate of function of many other systems in the body. Iodine and tyrosine are used to form both T3 and T4. The thyroid also produces the hormone calcitonin, which plays a role in calcium homeostasis.

The thyroid is controlled by the hypothalamus and pituitary. Hyperthyroidism (overactive thyroid) and hypothyroidism (underactive thyroid) are the most common problems of the thyroid gland.

Through the hormones it produces, the thyroid gland influences almost all of the metabolic processes in human body. Thyroid disorders can range from a small, harmless goiter that needs no treatment to life-threatening cancer. The most common thyroid problems involve abnormal production of thyroid hormones. Too much of these vital body chemicals results in a condition known as hyperthyroidism. Insufficient hormone production leads to hypothyroidism.

Diseases of Thyroid

Hypothyroidism (underactivity), Hyperthyroidism (overactivity), Goitre, Lingual thyroid, Thyroid adenoma and Thyroid cancer.

The Human Stomach – Functions, location, definition, anatomy, disease

The stomach is a hollow, muscular organ of the gastrointestinal tract (digestive system), between the esophagus and the small intestine. It is where digestion of protein begins. The stomach has three tasks. It stores swallowed food. It mixes the food with stomach acids. Then it sends the mixture on to the small intestine.

The human body: Human stomach

In humans, the stomach has a relaxed, empty volume of about 45 ml. It generally expands to hold about 1 litre of food, but can hold as much as 1.5 litres.

The stomach is supplied by both the parasympathetic and sympatethic parts of the autonomic nervous system.

Many stomach diseases are associated with infection. Historically, it was widely believed that the highly acidic environment of the stomach would keep the stomach immune from infection. However, a large number of studies have indicated that most cases of stomach ulcers, gastritis, and stomach cancer are caused by Helicobacter pylori infection.

The Human Spleen – Functions, location, definition, anatomy, disease

The human spleen is an organ found in humans with important roles in regard to red blood cells and the immune system.

It is located in the left upper quadrant of the abdomen.

The human body Human Spleen

The spleen is part of your lymphatic system, which fights infection and keeps your body fluids in balance. It contains white blood cells that fight germs. The human spleen also helps control the amount of blood in human body, and destroys old and damaged cells.

The spleen is encased in a thick connective-tissue capsule. Inside, the mass of splenic tissue is of two types, the red pulp and the white pulp, which do not separate into regions but intermingle and are distributed throughout the spleen. The white pulp is lymphoid tissue that usually surrounds splenic blood vessels. The red pulp is a network of channels (sinuses) filled with blood, and it is in the red pulp that most of the filtration occurs.

The Human Skin – Functions, location, definition, anatomy, disease

The skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system made up of multiple layers of mesodermal tissue, and guards the underlying muscles, bones, ligaments and internal organs.

Skin performs the following functions:

The human body skin
  • Protection: an anatomical barrier from pathogens and damage between the internal and external environment in bodily defense; Langerhans cells in the skin are part of the adaptive immune system.
  • Sensation: contains a variety of nerve endings that react to heat and cold, touch, pressure, vibration, and tissue injury.
  • Heat regulation: the skin contains a blood supply far greater than its requirements which allows precise control of energy loss by radiation, convection and conduction. Dilated blood vessels increase perfusion and heat loss while constricted vessels greatly reduce cutaneous blood flow and conserve heat.
  • Control of evaporation: the skin provides a relatively dry and semi-impermeable barrier to fluid loss. Loss of this function contributes to the massive fluid loss in burns.
  • Aesthetics and communication: others see our skin and can assess our mood, physical state and attractiveness.
  • Storage and synthesis: acts as a storage center for lipids and water, as well as a means of synthesis of vitamin D by action of UV on certain parts of the skin.
  • Excretion: sweat contains urea, however its concentration is 1/130th that of urine, hence excretion by sweating is at most a secondary function to temperature regulation.
  • Absorption: Oxygen, nitrogen and carbon dioxide can diffuse into the epidermis in small amounts. In addition, medicine can be administered through the skin, by ointments or by means of adhesive patch, such as the nicotine patch or iontophoresis. The skin is an important site of transport in many other organisms.
  • Water resistance: The skin acts as a water resistant barrier so essential nutrients aren’t washed out of the body.

The skin supports its own ecosystems of microorganisms, including yeasts and bacteria, which cannot be removed by any amount of cleaning.