Human Body

The human body is made up of thousands of cells, which are joined together to form tissues, organs and systems. The various systems of the human body work together to guarantee the functioning of the organism as a whole and, consequently, our survival.

In general, considering the cell as a functional and structural unit of living beings and the first level of organization of the organism, we have the following levels of organization of the human body:


Cells → Tissues → Organs → Systems → Organism

Read also: Levels of organization of the human body

→ Human body cells

The cells that form our body are called eukaryotes, which differ from prokaryotic cells in that they have a nucleus delimited by the nuclear membrane and membranous organelles, such as the Golgi complex, endoplasmic reticulum and mitochondria.

The human body has a series of cells with different shapes and functions.

In the human body, different types of these cells are found, each with adaptations related to the activity it performs. The following are some important cells in the human body and their respective activities:

  • Red blood cells or erythrocytes:anucleated cells of a biconcave shape that act in the transport of oxygen throughout the body.
  • Leukocytes:colorless cells related to the protection of the body against infections. There are different types of leukocytes: neutrophils, eosinophils, basophils, lymphocytes and monocytes.
  • Osteoblasts: cells responsible for producing the organic part of the bone matrix.
  • Osteocytes:mature cells derived from osteoblasts found within gaps in the bone matrix.
  • Osteoclasts:mobile cells that act in the reabsorption of bone tissue.
  • Adipocytes: cells that store fats.
  • Neurons:cells of the nervous tissue that guarantee the transmission of nerve impulses.
  • Glial cells: term used to designate some cell types of the nervous system. Glial cells are called: oligodendrocytes, Schwann cells, microglia astrocytes and ependymal cells.
  • Sperm: male gametes.
  • Oocyte: female gamete.

→ Human body tissues

Tissues can be defined as a group of similar cells that act together performing a specialized function. In the human body, four basic types of tissue are found:

Also read: Main human tissues

  • Epithelial tissue:characterized by juxtaposed cells with little extracellular matrix. Its cells are responsible for coating surfaces and secreting substances.

Tissue with cells close to each other and with little extracellular matrix.

  • Connective tissue:characterized by its large amount of extracellular matrix. There are types of connective tissue: blood , bone , cartilage , adipose tissue and connective tissue itself.
  • Muscle tissue: it ischaracterized by the presence of elongated cells with contraction capacity. There are three types of muscle tissue: non-striated muscle tissue, skeletal muscle tissue, cardiac muscle tissue.

Muscle tissue can be divided into three basic types: non-striated muscle tissue, skeletal muscle tissue, cardiac muscle tissue.

  • Nerve tissue:presents cells capable of generating, receiving and transmitting nerve impulses.

→ Organs of the human body

The various tissues of our body come together to form so-called organs, which have different functions and are assembled in different systems. In some cases, the same organ may belong to more than one system, being the case, for example, of the pancreas. The pancreas acts both in digestion (digestive system) and in the regulation of glucose levels through the production of the hormones insulin and glucagon (endocrine system).

The human body has a series of organs, which are grouped in various systems.

Don’t stop now … There’s more after the publicity;)

See below the characteristics of some of the organs found in the human body:

  • Heart: rich in muscle tissue, it is the organ that pumps blood to various parts of the body. Thus, the heart is essential to ensure that oxygen and nutrients are distributed throughout the body.

The heart is an organ belonging to the cardiovascular system.

  • Pituitarygland : an important gland in the endocrine system responsible for the production of growth hormone, prolactin, follicle stimulating hormone, luteinizing hormone, pituitary stimulating hormone (TSH) and adrenocorticotropic hormone.
  • Esophagus:muscular tube that ensures that the bolus flows from the mouth to the stomach.
  • Stomach:dilated portion of the digestive tract that acts by transforming the bolus into chyme through the action of the famous gastric juice.
  • Small intestine: in this organ, the final process of food digestion is observed. It is about 5 meters long and is responsible for a great absorption of nutrients.

The liver is related to the elimination of toxic substances and the production of bile.

  • Liver: it is the second largest organ in the human body, second only to the skin. This organ acts in the processing of substances that have been absorbed in the digestive tract. It is responsible, among other functions, for the neutralization and elimination of toxic substances. The liver is also responsible for the production of bile, a substance that works by emulsifying fats.
  • Lungs:respiratory organs formed by millions of alveoli, which are small air sacs located at the tips of the bronchioles. It is in the alveoli that the so-called gas exchange occurs.
  • Kidneys: bean-shaped organs found in pairs in the body. In it, urine is formed.
  • Bladder:organ responsible for storing urine, formed in the kidneys.
  • Uterus: anorgan of the woman’s body that has the function of sheltering the embryo during its development.

→ Human body systems

The organs present in the human body are grouped into tissues, which act to guarantee the functioning of the organism as a whole. The main systems of the human body are:

The systems of the human body are formed by a series of organs that work to perform a certain function.

  • Cardiovascular: this system has as its primary function to guarantee the distribution of oxygen and nutrients to all the cells of the body by pumping blood.
  • Digestive: system responsible for guaranteeing the processing of food, removing from these products the nutrients necessary for our survival and eliminating the unused parts.
  • Endocrine: system formed by the endocrine glands, which produce hormones , which act in various activities of our body.
  • Skeletal: system related to the locomotion of our body, protection of internal organs, storage of salts, such as calcium, and production of blood cells.
  • Excretory: system responsible for the production and elimination of urine.
  • Muscular: in addition to being related to the movement of our body, this system acts in the contraction of some organs.
  • Nervous: system responsible for perceiving, interpreting and responding to internal and external stimuli.
  • Reproducer: system responsible for the production of female and male sex hormones and for the production of gametes. In addition, it is in the female reproductive system that the embryo develops.
  • Respiratory: system that allows gas exchange in our body, that is, that guarantees the capture of oxygen and the release of carbon dioxide.
  • Integumentary: system consisting of skin and its attachments (hair, nails and glands). It acts mainly as a barrier, preventing the entry of microorganisms and the excessive loss of water.


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