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Gen. Bio

Human Body Systems Summary -Circulatory, Respiratory, Skeletal & Muscular  (GENERAL BIOLOGY)

The heart powers the circulatory system, pumping blood through the body to supply all cells with food and oxygen and to remove wastes. The muscles and bones work together to support and move the body using energy from respiration of this food and oxygen.

Circulatory system: How are materials carried around your body?

The circulatory system transports oxygen, carbon dioxide, heat, food, chemical messengers (hormones) and waste products in the blood. It is also a repair and defence system.

Human blood

The blood contains red blood cells, white blood cells, platelets and plasma. Red blood cells carry oxygen. White blood cells fight disease. Platelets help the blood to clot. Plasma is a liquid which carries dissolved food and other substances.

Human heart

The heart is an organ which pumps blood around the body to transport food, oxygen, hormones, heat and wastes.

The heart is made of cardiac muscle and is controlled by the autonomic nervous system.

The heart has two sides- the right side pumps blood to the lungs to pick up oxygen (pulmonary circulation); the left side pumps blood around the rest of the body (systemic circulation).

The heart is divided into four chambers– right and left atria and ventricles with valves between them.

The heart rate is measured in beats per minute. A pulse can be felt where an artery is close to a bone near the skin.

Cell respiration

During exercise, the muscles use more energy for respiration, so the heart must pump blood faster through the body.

Aerobic respiration is the process of using oxygen to get the energy from food in the mitochondria of all body cells. Carbon dioxide and water are waste products.

Anaerobic respiration in muscles converts sugar to lactic acid to give energy, and does not need oxygen. This gives extra power for the muscles but can only be sustained for a few seconds.

After exercise, the muscles may have an oxygen debt, so the heart rate stays high until this is cleared.

Blood vessels

The vascular system has a network of arteries, veins and capillaries, and these have a structure adapted to their function.

Atherosclerosis is a condition in which an artery wall thickens by build up of fatty materials such as cholesterol.

Blood pressure is measured using a sphygmomanometer. The most common units of pressure used are mmHg (millimetres of mercury).

A healthy adult blood pressure is around 140 over 80 . There are two numbers because one is the systolic pressure which is the maximum pressure when the heart contracts. The other is the diastolic pressure which is the minimum pressure when the heart relaxes and fills with blood.

Skeletal system: What supports and protects your body?

Bones give support, structure and protection, as well as allowing movement.

There are around 200 bones in the human body, including the Cranium and Mandible; Cervical vertebrae, Thoracic vertebrae, Lumbar vertebrae, Sacrum and Coccyx; Clavicle, Scapula, Sternum, Manubrium, Ribs and Pelvic girdle; Radius, Ulna and Humerus in the arm; Femur, Patella, Tibia and Fibula in the leg; and Tarsals, Metatarsals, Carpals, Metacarpals, and Phalanges in the hands and feet.

Bones are built from the mineral calcium phosphate, and have a hollow tubular structure which makes them strong and light.

Bones meet at joints, which can be fibrous (fixed), cartiliginal (a little movement) or synovial (full movement).

Joints can be ball and socket, hinge, sliding or saddle to give movement in different directions.

Ligaments connect bones across joints.

Muscular system: What moves the bones?

The heart is built from specialized cardiac muscle.

Smooth muscles control internal movements such as the churning of the stomach.

Skeletal muscles allow movement. They can only produce force by pulling, so are often found in antagonistic pairs around a joint.

Muscles are attached to bone by tendons.

There are around 600 muscles in the human body, and some of the most important are the Triceps, Biceps, Deltoids, Pectorals, Trapezius, Gluteals, Quadriceps, Hamstrings, Gastrocnemius, Latissimus dorsi, and Abdominals.

Respiratory system: Do you breathe in oxygen and breathe out carbon dioxide?

Breathing enables gas exchange which supplies red blood cells with oxygen and removes the waste product carbon dioxide.

The respiratory system consists of the nose, mouth, larynx, pharynx, trachea, and lungs, The lungs are found in the thorax.

To breathe in, the intercostal muscles contract, the ribs move up and out, and the diaphragm moves down. This increases the lung volume and pulls air into the alveoli where gas exchange takes place.

Oxygen diffuses from the lungs into the red blood cells, and carbon dioxide from the blood into the lungs.

To breathe out, the intercostal muscles relax, the diaphragm moves down and air is forced out of the lungs.

Concentration of carbon dioxide in the blood determines breathing rate.

Epidemiology: Why is a double blind test considered the ‘gold standard’ for scientific research and why is it often difficult to carry out?

Scientists investigate causal links between heart disease and various risk factors (smoking, diet etc.) by studying disease in large populations.

A double blind test is one where neither the researcher nor the experimental subject know which experimental group they have been assigned to. A placebo is often given to the control group.

A fair test is difficult when using human or other biological experimental subjects because it is difficult to control all variables. A large sample size is used where possible to reduce the effect of individual variation. There are often also ethical problems with researching human health.

©️World of Science
-Aristotle