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The Integumentary SystemThe Gastrointestinal System
The Musculoskeletal System
The Urinary/Excretory System
The Endocrine System
The Immune System
The Nervous System
The Integumentary System
The immune system defneds the body against attacks from foreign bodies (bacteria and viruses). The lymph glands and bone marrow work together to create and store the various types of white blood cell required to properly defend the body. The circulatory system is made up of the cardiovascular system (CV) and the Lymphatic system (L). This system is responsible for transporting nutrients and gases to the cells and tissues of the body, and removing waste products. The respiratory system provides oxygen for all your cells, and removes carbon dioxide from the body. The lungs are adapted to provide as large a surface area as possible to maximise diffusion. The small sacs in the lungs (alveoli) are only a cell thick to allow oxygen to diffuse into the blood and carbon dioxide to diffuse out. The gastrointestinal system is responsible for digestion of our food. Digestion is the process of breaking down food into nutrients that can be readily absorbed and used by the body. Most of the nutrients are absorbed in the small intestine, whereas the large intestine reabsorbs as much water as possible. The liver and pancreas aid digestion by producing bile (to digest fat) and enzymes, respectively.
The musculoskeletal system is a combination of the muscles and skeleton. The skeleton not only provides a rigid structure for the muscles to pull on, but provides protection to vulnerable internal organs such as the brain, lungs and heart. Muscles come in two varieties: skeletal and smooth. Skeletal muscle is under our conscious control and are attached to bones by rings of tissue called ligaments. Smooth muscle forms the walls of organs such as the stomach; this muscle cannot be controlled and is called involuntary. The kidneys are the major organs of the excretory system; they filter the blood removing urea, excess salt and water. These waste products are stored in the bladder until they can be excreted from the body. The two major blood vessels of the body, the aorta and vena cava supply the kidneys with blood. The human reproductive system is the only organ system that differs betwen the sexes. It allows couples to produce fertile offspring to continue the species. Women are born with their full complement of immature eggs (between 400,000 and 2 million), inside their ovaries*. Men constantly produce sperm from puberty at the rate of around 1,500 sperm per second. The human endocrine system is a collection of glands that secrete hormones - the chemical messengers of the human body. These molecules cause chemical changes in cells with the appropriate receptors. For example, growth hormones secreted by the pituitary gland signal certain cells to divide for growth. The adrenal glands release adrenaline (epinephrine) under stress to trigger the fight-or-flight response. The endocrine system works together with the nervous system to send messages around the body. The nervous system is high-speed broadband compared to the postal service that is the endocrine system. It transmits electrical messages at high speed from throughout the body. There are four different types of nerves: 1. Cranial nerves run from the brain to the sense organs of the head. 2. Central nerves are found in the brain and spinal cord. 3. Autonomic Nerves run from the spinal cord to the lungs, heart, digestive, bladder and sex organs. Thesesendmessagesthatarenotunderconsciouscontrol. 4. Peripheral nerves connect the spinal cord to the limbs - these messages are under conscious control and are used for things such as movement. The skin is the largest organ of the body - it makes up 16% of your body weight - and one of our most important sense organs. It also regulates body temperature, provides a physical barrier to pathogens, protects internal organs and helps to retain moisture. Fast Fact: The tissue that makes up your heart is myogenic - it will beat on its own! Fast Fact: The lungs provide a surface area of over 70m2 in an adult - this is the size of a tennis court! Fast Fact: The small intestine can be up to 20ft (6m) in length Fast Fact: There are 206 bones in an adult body, but babies have more than 300 bones or cartilage elements! Fast Fact:Healthy urine is sterile - it contains fluids and salts, but no bacteria or viruses...so it is safe to drink? Fast Fact: While a woman may be born with 2 million eggs, only around 500 eggs will develop over the course of her fertile life. Fast Fact:There are around 50 different hormones in the human body. Fast Fact: It is thought that new cancer therapies can be developed by modifying and targetting the body's own immune system - this could lead to cancer treatments with no side-effects. Fast Fact:The brain contains over 100 billion neurons! Fast Fact: The outer layer of the skin is made of dead cells - we shed around 30,000-40,000 an hour (out of 1.6 trillion skin cells). This forms most of the dust in your house. Over a year you shed around 3.6kg (8lbs) of dead skin. Date: 2016-01-03; view: 973
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