Human Body Summary

Updated: 21.04.2020

Human Body Summary

Parts of the body: head, neck, trunk (torso) and limbs (arms and legs)
Types of tissue: lining cells (epithelia), connective tissue, nervous tissue and muscle tissue
Organ systems: respiratory, digestive, cardiovascular, urinary, integumentary, skeletal and muscular, endocrine, lymphatic, nervous and reproductive
Other systems: immune, exocrine


Circulatory system: permits blood to circulate
          blood, blood vessels (arteries, veins, capillaries) and heart
Lymphatic system: returns filtered blood plasma as lymph, transports white blood cells and cells related to immunity response
          lymph, lymph nodes and vessels
Digestive and excretory system: digestion and absorption of food, metabolism
          gastrointestinal tract (mouth, oropharynx, esophagus, stomach, small and large intestines, and the anus) and accessory organs
Endocrine system: a chemical messenger via a system of hormones
          endocrine glands (pineal gland, pituitary gland, pancreas, ovaries or testes, thyroid gland and parathyroid gland, hypothalamus and adrenal glands)
Integumentary system: protects the body from damage, generates vitamin D
          skin, hair and nails
Muscular system: permits movement of the body, maintains posture and circulates blood
          skeletal, smooth and cardiac muscles
Skeletal system: internal framework of the human body, protects major organs
          206 bones, axial and appendicular skeleton
Nervous system: coordinates actions and sensory information
          CNS - central (brain and spinal cord) and PNS - peripheral (somatic, automatic and enteric)
Reproductive system: sexual reproduction
          male (sperm, penis, testicles, sperm ducts, prostate) and female (egg cell, uterus, ovaries, vagina, vulva)
Respiratory system: exchange of gasses
          upper (nose and mouth, nasal cavities and paranasal sinuses, pharynx and larynx) and lower (trachea, bronchi, alveoli, lungs) respiratory tract
Urinary system: eliminates waste
          kidneys, ureters, bladder, and urethra



Exocrine system: a system of hormones and glands
          salivary glands, sweat glands, ciliary, ceruminous lacrimal, meibomian, sebaceous, mucous and mammary glands
Immune system: protects against disease
          thymus, bone marrow, tonsils, lymph vessels and nodes



The human body is the structure of a human being. It contains trillions of cells, the fundamental units of life. The adult male body is about 60% water. The human body comprises of a head, neck, trunk, which includes the thorax and abdomen, and limbs, arms and hands, and legs and feet. The shape of a human body is determined  mainly by the skeleton, but also by the distribution of muscle and fat.
          The whole body is covered by the skin. There are five main senses, sight, hearing, smell, taste and touch. There are four main cavities, cranial, spinal, thoracic ans abdominopelvic, divided into abdominal and pelvic cavities.
          The head is the seat of the brain and several sense organs and it is supported by seven cervical vertebrae. It consists of the skull which encloses the brain and is covered by the scalp with hair and the face.
          The neck joins the head and the trunk, it supports the weight of the head, protects the spine and allows movement.
          The trunk, also called torso, is the central part of the body and houses many critical organs. The diaphragm divides the torso into the thoracic cavity and the abdominal cavity. The upper chest is protected by the rib cage.
          There are two upper and two lower extremities, also called limbs. The upper limb, the arm, is divided into the shoulder, the upper arm, the elbow, the forearm, the wrist and the hand, which is composed of the back and the palm, four fingers and a thumb. The leg is attached to the pelvic girdle. It is constituted of the hip, the thigh, the knee, the lower leg with the shin in the front and a calf at the back, the ankle and the foot with the instep, the sole, the arches and five toes.
     

The body consists of many different types of tissue, defined as cells that act with a specialized function. There are four main types of tissues, lining cells (epithelia), connective tissue, nervous tissue and muscle tissue. Endothelial cells line internal cavities including blood vessels and glands.
       
Organs are structured collections of cells with a specific function. An organ system is a group of organs that work together as a biological system to perform one or more functions. There are eleven distinct organ systems in human beings, respiratory, digestive, cardiovascular, urinary, integumentary, skeletal and muscular, endocrine, lymphatic, nervous and reproductive. The immune system is not an organ system. On the other hand, some organs are in more than one system.
          The circulatory system permits blood to circulate and transport nutrients, oxygen and carbon dioxide, hormones and blood cells from and to the cells to provide nourishment, stabilize temperature and pH and maintain homeostasis. The system comprises blood, heart and blood vessels and it is connected to the lymphatic system. Pulmonary circulation leads oxygen-poor blood under low pressure from the heart through the lungs where it is oxygenated. Systemic circulation is a loop through the rest of the body to provide oxygenated blood. Arteries are blood vessels that deliver oxygen-rich blood from the heart to the tissues of the body and veins carry deoxygenated blood from the tissues towards the heart. The heart is a hollow muscular organ which pumps oxygenated blood to the body and deoxygenated blood into the lungs.
          The lymphatic system returns filtered blood plasma as lymph. It comprises of lymph, lymph nodes and lymph vessels. Lymph is a clear fluid, it contains lymphocytes, a subtype of white blood cells.
          The immune system is a host defense system that protects against disease. To function properly, it must detect a wide variety of pathogens.  The key organs are thymus, bone marrow, spleen, tonsils, lymph vessels and nodes, adenoids, skin and liver.
          The function of the digestive system is digestion, absorption and metabolism. It is composed of the gastrointestinal tract and accessory organs. The gastrointestinal tract is made of the mouth, oropharynx, esophagus, stomach, small and large intestines, and the anus. The accessory organs are the liver, gallbladder and pancreas, their secretion flow into the small intestine and bring chemicals in food. Some parts of the digestive system are also part of the excretory system, a passive biological system that removes excess, unnecessary material from the body to help maintain homeostasis and prevent damage.
          The endocrine system is a chemical messenger system of hormones released by internal glands into the circulatory system. The major glands include the pineal gland, pituitary gland, pancreas, ovaries or testes, thyroid gland and parathyroid gland, hypothalamus and adrenal glands.
          The integumentary system includes skin, hair and nails. Its function is to protect the body from various kinds of damage, changes of temperature and dehydration, and it generates vitamin D through exposure to ultraviolet light.
           The exocrine system is a system of hormones and glands, where the glands secrete straight to a target site. It includes the salivary glands, sweat glands, ciliary, ceruminous lacrimal, meibomian, sebaceous, mucous and mammary glands. These glands work independently responding to the needs of the body.
          The muscular system is an organ system consisting of skeletal, smooth and cardiac muscles. It permits movement of the body, maintains posture and circulates blood throughout the body, it provides strength, balance, and heat.
          The skeletal system is the internal framework of the human body. It is composed of  around 206 bones by adulthood. The human skeleton can be divided into the axial skeleton and the appendicular skeleton. The axial skeleton consists of 80 bones and is formed by the vertebral column 32-34 bones), the rib cage (12 pair bones and the sternum), the skull and other (22 bones and 7 associated bones). The appendicular skeleton, which is attached to the axial skeleton, consists of 126 bones divided into six major regions, as it is formed by the shoulder girdle, the pelvic girdle and the bones of the upper and lower limbs.

          The nervous system is a highly complex part of the human body that coordinated its actions and sensory information by transmitting signals to and from its different parts. It consists of the central nervous system (CNS) and the peripheral nervous system (PNS).
          The reproductive system is a system of sex organs which work together for the purpose of sexual reproduction. The male reproductive system is a series of organs primarily located outside the body that have one function, to produce and deposit sperm. The main male sex organs are the penis and the testicles, the internal parts are the epididymis, sperm ducts and three glands, for example the prostate. The female reproductive system is a series of organs primarily located inside the body which have two functions, to produce egg cells and to protect and nourish the fetus until birth. The main female sex organs are the uterus, Fallopian tubes, ovaries and the vagina, the external part is the vulva.
          The respiratory system is associated with the exchange of gasses, oxygen and carbon dioxide, between the human body and the environment, and also between the tissue cells and the blood. These functions are achieved by ventilation, which consists of two acts, inspiration and expiration. The upper respiratory tract is formed by the nose and mouth, nasal cavities and paranasal sinuses, pharynx and larynx. The lower respiratory tract consists of the trachea, bronchi, bronchioles and the alveoli inside two lungs.

          The urinary system consists of the kidneys, ureters, bladder, and the urethra. It functions to eliminate waste from the body, regulate blood volume and blood pressure, control levels of electrolytes and metabolites, and regulate blood pH.