Organs

What are organs?

Organs are separate functional units of our body consisting of different tissues. Each organ fulfills a specific task – from the lungs, which allow us to breathe, to the heart, which tirelessly pumps blood through our veins – and together they keep our body alive. Despite independent functions, these work together in a network or “system”.

The most important organ groups

The organs of the human body can be divided into different functional groups or organ systems:

Nervous system

The nervous system is a network of specialized cells (so-called nerve cells). It is used for stimulus perception, stimulus processing and reaction control.

The nervous system consists of two main parts:

1. Central nervous system (CNS)
   • Brain: controls thoughts, movements, feelings and many bodily functions
   • Spinal cord: connects the brain with the rest of the body and transmits signals
2. Peripheral nervous system (PNS)
   • All nerves that lie outside the brain and spinal cord
   • Receive signals from sensory organs and transmit them to the brain for processing. In turn, signals and commands can also be transmitted from the brain to the muscles, for example.

Task of the nervous system

• Control of movements
• Perception of stimuli (e.g. pain, temperature)
• Control of organ functions (e.g. breathing, heartbeat)
• Processing of information
• Regulation of reflexes (e.g. knee reflex)

The nervous system works with electrical and chemical signals to quickly transmit information throughout the body.

Cardiovascular system

The task of the cardiovascular system is to transport blood to all of the body’s cells. The oxygen in the blood can thus be transported to the cells. However, waste products, nutrients and other important cells such as platelets, coagulation factors and immune cells can also be transported from place to place.

The cardiovascular system consists of several elements.

• blood vessels:
  • Arteries: transport oxygen-rich blood from the heart to the organs
  • Veins: transport deoxygenated blood back to the heart
  • Capillaries: fine vessels in which the exchange of oxygen, nutrients and waste products takes place
  • Lymphatic vessels: transport of immune cells and water.

• HeartThe left heart takes oxygen-rich blood from the lungs and pumps it through the body. The right heart takes venous oxygen-poor blood and pumps it through the lungs to enrich it with oxygen.
• Blood: transports oxygen, nutrients and waste products

Tasks of the cardiovascular system

• Supply the organs with oxygen and nutrients
• Removal of waste materials such as carbon dioxide
• Support for the immune system
• Regulation of body temperature
• Transport of hormones, proteins, nutrients

Respiratory system

The lungs are an organ system that supplies the body with oxygen and removes carbon dioxide as a waste product. It also performs many other important tasks and consists of:

• Nose and mouth: entrance for the air we breathe
• Throat (pharynx): directs the air to the windpipe
• Windpipe (trachea): connects the throat with the bronchi
• Bronchi: distribute the air into the lungs
• Lungs: absorb oxygen and release carbon dioxide
• Pulmonary alveoli: this is where gas exchange takes place
• Respiratory muscles: Muscle that supports breathing, such as the diaphragm

Task of the respiratory system

• Absorption of oxygen from the air
• Release of carbon dioxide
• Support in regulating the acid-base balance in the body
• Immunological tasks
• Participation in voice training (via the larynx)

The respiratory system works closely with the cardiovascular system, as oxygen is transported in the blood to the organs.

Digestive system

The digestive system is an organ system that absorbs food, breaks it down into nutrients and eliminates waste from the body.

Components of the digestive system

• Mouth: Crushes the food and mixes it with saliva
• Esophagus: transports food into the stomach
• Stomach: Breaks down food with stomach acid and enzymes
• Small intestine: Breaks down food further and absorbs nutrients into the bloodstream
• Large intestine: extracts water from food and forms the stool
• Rectum and anus: excrete the indigestible remains

Task of the digestive system

• Food intake
• Breakdown of food into small components (e.g. sugar, fats, proteins)
• Absorption of nutrients into the blood
• Removal of waste materials
• Immunological tasks

The digestive system works closely with the cardiovascular system, as the absorbed nutrients are transported to the organs via the blood.

Urogenital system

The urogenital system is an organ system that controls urine production, urination and reproduction.

The urogenital system consists of two parts:

1. urinary system (urinary tract)

• Kidneys: filter the blood and produce urine
• Ureters: carry urine from the kidneys to the bladder
• Urinary bladder: stores the urine
• Urethra: drains urine from the body

2. sexual system (genital system)

• Male reproductive organs: testicles, vas deferens, prostate, penis
• Female reproductive organs: ovaries, fallopian tubes, uterus, vagina

Task of the urogenital system

• Urinary system:
  • Filtering the blood
  • Excretion of waste products via the urine
  • Regulation of the water and salt balance
• Gender system:
  • Formation of gametes (sperm or egg cells)
  • Reproduction
  • Production of sex hormones

The urogenital system combines important functions: Removal of waste products, regulation of the salt and water balance, and reproduction.

Musculoskeletal system

The musculoskeletal system (also known as the musculoskeletal system) is an organ system that gives the body stability, enables movement and protects the internal organs.

Components of the musculoskeletal system

• Bones: form the skeleton and give the body support
• Joints: connect the bones with each other and enable movement
• Muscles: move the bones and support posture
• Tendons: connect muscles with bones
• Ligaments: connect bones together and stabilize the joints
• Cartilage: protects the joints and absorbs shocks

Tasks of the musculoskeletal system

• Enabling movements
• Stabilization of the body
• Protection of the internal organs
• Storage of minerals (e.g. calcium in the bones)
• Production of blood cells in the bone marrow

The musculoskeletal system works closely with the nervous system, as nerves control the movements of the muscles.

Endocrine system

The endocrine system is an organ system consisting of glands that produce hormones and release them into the bloodstream to regulate various bodily functions.

Components of the endocrine system

• Pituitary gland (hypophysis): Control center for many hormones
• Thyroid gland: regulates the metabolism
• Parathyroid glands: regulate the calcium and phosphate balance
• Adrenal glands: produce hormones that influence the metabolism, the immune system and the stress response mechanism
• Pancreas: produces insulin and glucagon to regulate blood sugar levels
• Gonads (ovaries and testicles): produce hormones that control reproduction and sexual characteristics
• Pineal gland (pineal gland): produces melatonin, which regulates the sleep-wake rhythm
• However, many other organs are hormonally active

Task of the endocrine system

• Regulation of the metabolism
• Managing growth and development
• Influence on reproduction
• Regulation of the fluid and electrolyte balance
• Support for stress management and the immune system

The endocrine system works by releasing hormones that are transported as chemical messengers via the blood to target cells in the body in order to change their activity.

Immune system

The immune system is the body’s defense system that protects it from pathogens such as bacteria, viruses, fungi and other harmful substances.

Components of the immune system

• Immune cells: circulate in the blood and fight invaders
• Lymph nodes: filter lymph fluid and store immune cells
• Spleen: removes old blood cells and helps fight infections
• Thymus: forms and matures T cells (important immune cells)
• Bone marrow: produces blood cells, including white blood cells
• Antibodies: proteins that are produced by B cells and mark pathogens
• Lymph fluid: transports immune cells and waste products

Tasks of the immune system

• Recognition of and defense against pathogens: combating infections by identifying foreign substances (antigens)
• Destruction of infected or abnormal cells: protects against diseases such as cancer
• Memory of previous infections: the immune system “remembers” pathogens so that it can react more quickly in the event of renewed contact (immunity)

The immune system is complex and works on different levels to protect the body, including the so-called non-specific defense (e.g. skin and mucous membranes) and the specific defense (e.g. antibodies and T cells).

Skin

The skin is the largest organ of the human body and serves as a protective barrier between the inside of the body and the outside environment.

Components of the skin

• Epidermis: The protective outer layer
• Dermis: Rich in blood vessels and nerve endings
• Subcutis: fatty tissue as an energy store and insulator

Tasks of the skin

• Protection: It protects against physical injuries, infections and harmful environmental influences such as UV radiation.
• Temperature regulation: The skin helps to regulate body temperature by producing sweat when it is hot and constricting blood vessels when it is cold.
• Sensory perception: It contains receptors that perceive touch, pain, temperature and pressure.
• Excretion: It excretes some waste products with the sweat.
• Vitamin D production: UV radiation produces vitamin D in the skin, which is important for bone health.
• Immunological tasks

The skin has an important protective function and is essential for the well-being of the body.

Interaction of the organs

This classification provides an overview – but does not take into account the numerous overlaps and interactions between the organ systems.

No organ system acts completely independently of the others, and some organs, such as the liver, fulfill functions in several systems. Communication between organs enables the body to adapt the tasks of each individual organ to the needs of the whole organism. This is crucial for the efficient functioning of the body as a whole.

The importance of organs in medicine

In human medicine, an understanding of organ functions and their interactions is crucial for:

• the diagnosis of diseases
• the development of targeted therapies
• the prevention of diseases
• The research and treatment of organ diseases is a focus in various medical specialties such as internal medicine, surgery and transplantation medicine

Understanding the individual organ functions is crucial for the diagnosis and treatment of diseases. However, due to the complex interactions between the various organs, medicine is becoming less and less organ-centered.