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* (Muscular System (Skeletal Muscles, Cardiac Muscles, Smooth Muscles),…

- - - - Connective Tissue
        
        Tendons connect muscles to bones. Tendons help form a connection between soft contracting muscle cells to hard bone cells.
        
        Ligaments connect bones to bones holding the skeletal frame together.
- - - - Not too hot!
        Enzymes are made of protein. That is why it is important that they are not overheated. If they are too hot, they can become denatured. It’s a bit like cooking meat — once they are denatured, they can’t go back to how they were before, so they can’t work as enzymes anymore. Different enzymes operate best within specific temperature ranges.
    - - Liver
      - Your liver is an extremely important organ with many key roles. One of these is the production of bile, which is transported to your gall bladder via the bile ducts to be stored until it is needed. Bile is transported from the gall bladder to the small intestine where it is involved in the mechanical digestion of lipids such as fats and oils.
      - Pancreas
      - Enzymes, such as lipases, amylases and proteases, which break down lipids, carbohydrates and proteins respectively, are made by the pancreas and secreted into the small intestine to chemically digest these components of food.
      - Large Intestine
      - On its way through the digestive tract (alimentary canal), undigested food moves from the small intestine to the colon of the large intestine. It is here that water and any other required essential nutrients still remaining in the food mass may be absorbed into your body. Vitamin D manufactured by bacteria living within this part of the digestive system is also absorbed. Any undigested food, such as the cellulose cell walls of plants (which we refer to as fibre), also accumulates here and adds bulk to the undigested food mass.
      - The rectum is the final part of the large intestine where the faeces is stored before being excreted through the anus as waste.
      - Fat Products
      - Breaking down lipids, such as fats and oils, is hard work! Because lipids are insoluble in water, they tend to clump together into large blobs. Bile helps solve this problem. As half of the bile molecule is attracted to water and the other half attracted to lipids, it helps to emulsify or separate the lipids so the lipase enzymes can gain access to them and do their job. This is an example of mechanical digestion (bile) and chemical digestion (lipase) working together to get the job done!
- - - - The glomerulus filters water and small solutes out of the bloodstream. The resulting filtrate contains waste, but also other substances the body needs: essential ions, glucose, amino acids, and smaller proteins. When the filtrate exits the glomerulus, it flows into a duct in the nephron called the renal tubule. As it moves, the needed substances and some water are reabsorbed through the tube wall into adjacent capillaries. This reabsorption of vital nutrients from the filtrate is the second step in urine creation.
      - The filtrate absorbed in the glomerulus flows through the renal tubule, where nutrients and water are reabsorbed into capillaries. At the same time, waste ions and hydrogen ions pass from the capillaries into the renal tubule. This process is called secretion. The secreted ions combine with the remaining filtrate and become urine. The urine flows out of the nephron tubule into a collecting duct. It passes out of the kidney through the renal pelvis, into the ureter, and down to the bladder.
        The nephrons of the kidneys process blood and create urine through a process of filtration, reabsorption, and secretion. Urine is about 95% water and 5% waste products. Nitrogenous wastes excreted in urine include urea, creatinine, ammonia, and uric acid. Ions such as sodium, potassium, hydrogen, and calcium are also excreted.
- - - - It is important for bones to be strong to support our body weight and in some cases provide protection such as the skull and ribs. However, they must also be light enough to make movement possible. The largest and longest bone in the human body is the femur which is found in both legs.
      - The diagram above shows the internal and external composition of the bone:
      - a) Bone Matrix:
      - The bone matrix is made up of inorganic elements which are Ca, P, Mg, K, and Na. It also contains collagen fibres and protein. Collagen gives bone its tensile strength, namely the resistance to being pulled apart. Hydroxyapatite gives the bones compressive strength or resistance to being compressed.
      - b) Bone Cells:
      - There are four types of bone cells found in our skeleton.
      - They are:
      - Osteo-progenitor cells (pre-osteoblasts): They form a population of stem cells that can differentiate (change) into the more specialised bone-forming cells (osteocytes and osteoblasts).
      - Osteocytes (inactive osteoblast): These are inactive osteoblasts that have become trapped in the bone that they have created. They maintain connections to other osteocytes and osteoblasts. They are important for communication within bone tissue.
      - Osteoblasts (bone forming cells): These are responsible for making new bone and repairing older bone. Osteoblasts produce a protein mixture called osteoid, which is mineralized and becomes bone. They also manufacture hormones, including prostaglandins.
      - Osteoclasts (bone resorbing cells): These are large cells with more than one nucleus. Their job is to break down bone. They release enzymes and acids to dissolve minerals in bone and digest them. This process is called resorption. Osteoclasts help remodel injured bones and create pathways for nerves and blood vessels to travel through.
      - c) Bone Marrow:
      - Is found in almost all bones where cancellous bone is present. The marrow is responsible for making around two million red blood cells every second. It also produces lymphocytes or the white blood cells involved in the immune system.
    - - Long bones: These are mostly compacted bone with little marrow and include most of the bones in the limbs. These bones tend to support weight and help movement.
      - Short bones: Only a thin layer of compact bone, these include bones of the wrist and ankle.
      - Flat bones: Usually bones that are thin and curved. They consist of two outer layers of compact bone and an inner layer of spongy bone. Flat bones include most of the bones of the skull and the sternum or breastbone. They tend to have a protective role.
      - Sesamoid bones: These are embedded in tendons, such as the patella or kneecap. They protect tendons from wear and stress.
      - Irregular bones: As their name implies, these are bones that do not fit into the first four categories and are an unusual shape. They include the bones of the spine and pelvis. They are often protecting organs or tissues.
      - Bones of the skeleton are split into two groups. They are; appendicular skeleton — bones of the limbs, shoulders, and pelvic girdle, axial skeleton — bones of the skull, vertebral column, thoracic cage.
      - Joint Types:
      - A joint is a point where two or more bones meet. There are three main types of joints; Fibrous (immovable), Cartilaginous (partially moveable) and the Synovial (freely moveable) joint.