Human body

Escrito por lauravriveradiaz 12-03-2018 en Human Body. Comentarios (0)


Human body


The human body is the entire structure of a human being. It is composed of many different types of cells that together create tissuesand subsequently organ systems. They ensure homeostasis and the viability of the human body.

                                                                                             


It comprises a head, necktrunk (which includes the thorax and abdomen), arms and hands, legs and feet.

The study of the human body involves anatomyphysiologyhistology and embryology. The body varies anatomically in known ways. Physiology focuses on the systems and organs of the human body and their functions. Many systems and mechanisms interact in order to maintain homeostasis, with safe levels of substances such as sugar and oxygen in the blood.

The body is studied by health professionals, physiologists, anatomists, and by artists to assist them in their work.


Composition


The human body is composed of elements including hydrogenoxygencarboncalcium and phosphorus. These elements reside in trillions of cells and non-cellular components of the body.

The adult male body is about 60% water for a total water content of some 42 litres. This is made up of about 19 litres of extracellular fluid including about 3.2 litres of blood plasma and about 8.4 litres of interstitial fluid, and about 23 litres of fluid inside cells. The content, acidity and composition of the water inside and outside cells is carefully maintained. The main electrolytes in body water outside cells are sodium and chloride, whereas within cells it is potassium and other phosphates.


                                                                             


Cells

The body contains trillions of cells, the fundamental unit of life. At maturity, there are roughly 30–37 trillion cells in the body, an estimate arrived at by totalling the cell numbers of all the organs of the body and cell types. The body is also host to about the same number of non-human cells as well as multicellular organisms which reside in the gastrointestinal tract and on the skin. Not all parts of the body are made from cells. Cells sit in an extracellular matrixthat consists of proteins such as collagen, surrounded by extracellular fluids. Of the 70 kg weight of an average human body, nearly 25 kg is non-human cells or non-cellular material such as bone and connective tissue.


Tissues

The body consists of many different types of tissue, defined as cells that act with a specialised function. The study of tissues is called histology and often occurs with a microscope. The body consists of four main types of tissues – lining cells (epithelia), connective tissuenervous tissue and muscle tissue.

Organs


Organs, structured collections of cells with a specific function, sit within the body. Examples include the heartlungs and liver. Many organs reside within cavities within the body. These cavities include the abdomen and pleura.


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Circulatory system


The circulatory system comprises the heart and blood vessels (arteriesveins and capillaries). The heart propels the circulation of the blood, which serves as a "transportation system" to transfer oxygen, fuel, nutrients, waste products, immune cells and signalling molecules (i.e., hormones) from one part of the body to another. The blood consists of fluid that carries cells in the circulation, including some that move from tissue to blood vessels and back, as well as the spleen and bone marrow.


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Digestive system


The digestive system consists of the mouth including the tongue and teethesophagusstomach, (gastrointestinal tractsmall and large intestines, and rectum), as well as the liverpancreasgallbladder, and salivary glands. It converts food into small, nutritional, non-toxic molecules for distribution and absorption into the body.


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Endocrine system


The endocrine system consists of the principal endocrine glands: the pituitarythyroidadrenalspancreasparathyroids, and gonads, but nearly all organs and tissues produce specific endocrine hormones as well. The endocrine hormones serve as signals from one body system to another regarding an enormous array of conditions, and resulting in variety of changes of function.


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Immune system


The immune system consists of the white blood cells, the thymuslymph nodes and lymph channels, which are also part of the lymphatic system. The immune system provides a mechanism for the body to distinguish its own cells and tissues from outside cells and substances and to neutralize or destroy the latter by using specialized proteins such as antibodiescytokines, and toll-like receptors, among many others.


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Integumentary system


The integumentary system consists of the covering of the body (the skin), including hair and nails as well as other functionally important structures such as the sweat glands and sebaceous glands. The skin provides containment, structure, and protection for other organs, and serves as a major sensory interface with the outside world.


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Lymphatic system


The lymphatic system extracts, transports and metabolizes lymph, the fluid found in between cells. The lymphatic system is similar to the circulatory system in terms of both its structure and its most basic function, to carry a body fluid.

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Musculoskeletal system


The musculoskeletal system consists of the human skeleton (which includes bonesligamentstendons, and cartilage) and attached muscles. It gives the body basic structure and the ability for movement. In addition to their structural role, the larger bones in the body contain bone marrow, the site of production of blood cells. Also, all bones are major storage sites for calcium and phosphate. This system can be split up into the muscular system and the skeletal system.

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Nervous system


The nervous system consists of the central nervous system (the brain and spinal cord) and the peripheral nervous system consists of the nerves and gangliaoutside the brain and spinal cord. The brain is the organ of thought, emotion, memory, and sensory processing, and serves many aspects of communication and controls various systems and functions. The special senses consist of visionhearingtaste, and smell. The eyes, ears, tongue, and nose gather information about the body's environment.

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Reproductive system


The reproductive system consists of the gonads and the internal and external sex organs. The reproductive system produces gametes in each sex, a mechanism for their combination, and in the female a nurturing environment for the first 9 months of development of the infant.

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Respiratory system


The respiratory system consists of the nose, nasopharynxtrachea, and lungs. It brings oxygen from the air and excretes carbon dioxide and water back into the air.

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Urinary system


The urinary system consists of the kidneysuretersbladder, and urethra. It removes toxic materials from the blood to produce urine, which carries a variety of waste molecules and excess ions and water out of the body.


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