Zoology lecture

• Skeletal system


  The basic framework of the body, consisting of all the bones and tissues associated with cartilages and joints
• Functions of the skeletal system

  • Sustains the body's weight
  • Promotes movement
• Long bones


  Serve to sustain the body's weight and promote movement, responsible for producing red and white blood cells
• Short bones


  Usually have the same length and width, offer support and flexibility in the ankle and wrist joints
• Flat bones


  Protect internal organs, including the heart, brain, and pelvic organs, relatively flattened and can act as a protection wall

  
• Irregular bones


  Differ in form and structure, cannot be classified under any other category, have a complex shape which helps in protecting internal organs

  
• Bones of the human body

  • Femur
  • Radius
  • Humerus
  • Clavicle

  
• Connective tissue


  Supports and connects different tissues and organs of the body
• Types of connective tissue

  • Loose connective tissue
  • Dense connective tissue
  • Specialised connective tissue
• Areolar tissue


  Present under the skin, supports epithelium, contains randomly distributed fibres, fibroblasts, mast cells and macrophages
• Adipose tissue


  Present under the skin, stores fat, acts as a shock absorber and helps in maintaining body temperature in colder environments
• Reticular connective tissue


  Made up of reticular fibres, supports the internal framework of organs such as liver, lymph nodes and spleen
• Articular cartilage


  Covers the ends of long bones at the joints, reducing friction and providing shock absorption
• Bone formation


  1. Osteoblasts secrete osteoids (unmineralized bone matrix) into the membrane of connective tissue columns known as trabeculae

  2. Calcification (calcium deposition) of osteoids leads to bone formation

  3. Cartilage skeleton hardens to form the bony skeleton

  4. Osteoblasts form the bone matrix and specialize in the mineralization of the bone cells

  
• Differences between spongy and compact bones

  • Spongy bones are light, spongy and soft, made up of trabeculae, fill the inner layer of most bones, form the ends or epiphyses of long bones
  • Compact bones are heavy, tough and compact, made up of osteons, fill the outer layer of most bones, form the shaft or diaphysis of long bones

  
• Parathyroid hormone


  Secreted by the four parathyroid glands, controls and regulates the levels of calcium in the blood and raises their levels when they are too low, acts on the bones, intestines, and kidneys
• Ball and socket joints


  One bone is hooked into the hollow space of another bone, allows for rotatory movement, examples are the shoulders and neck
• Pivotal joints


  One bone has tapped into the other in such a way that full rotation is not possible, allow for sideways and back-forth movement, example is the neck
• Gliding joints


  Also known as plane or planar joints, permit two or more round or flat bones to move freely together without any rubbing or crushing of bones
• Hinge joints


  Like door hinges, only allow back and forth movement, examples are the ankle, elbows, and knee joints
• Differences between troponin and tropomyosin

  • Troponin is a protein found in muscle cells that is important for muscle contraction, binds with calcium which leads to a change in its shape and renders the myosin sites active, promoting muscle contraction
  • Tropomyosin is a protein found in the cytoskeleton in the cytoplasm, functions to block the contact between myosin heads and actin filaments, thereby preventing muscle contraction
• Components of skeletal muscle fibers

  • Sarcoplasm (cytoplasm of a myocyte)
  • Sarcoplasmic reticulum (equivalent of the smooth endoplasmic reticulum in a myocyte)
  • Sarcolemma (cell membrane of a myocyte)
  • Sarcomere (functional contractile unit of the myofibril of a striated muscle representing the region between Z-lines)
• Serotonin


  A well-known neurotransmitter found in abundance in the digestive system, typically associated with depression
• Dopamine


  Known as a feel-good chemical, plays a role in Parkinson's disease
• Glutamate


  The most abundant amino acid in the brain, can lead to cell death due to its ability to elicit a toxic response in cells
• Acetylcholine


  Neurotransmitter that stimulates muscles to contract and plays an important role in various cognitive functions, such as memory, also associated with Alzheimer's disease
• Atrophy


  Decrease in the size of a body part, cell, organ, or other tissue
• Hypertrophy


  Increase in the size of cells and tissues, causing an increase in the size of their respective organs
• Hyperplasia


  Increase in the number of cells due to a higher rate of cell division
• Dysplasia


  Abnormal changes in the shape, size, and organization of mature cells
• Digestive enzymes

  • Amylase
  • Protease
  • Lipase
• Amylase


  Breaks starch into small carbohydrate molecules, produced by cells in the pancreas and travels via a duct to reach the small intestine
• Protease


  Breaks down protein into amino acids, special cells produce an enzyme called pepsinogen in the stomach that converts into pepsin when it comes in contact with the acid
• Lipase


  Breaks down dietary fats into smaller molecules known as glycerol and fatty acids, a little quantity of lipase, known as gastric lipase, is produced by the cells of the stomach
• Regions of the small intestine

  • Duodenum (shortest region)
  • Jejunum (most absorption takes place)
  • Ileum (food starts to solidify leaving no nutrients)
• Functional units

  • Kidney (nephrons produce waste products such as urea and ammonia)
  • Liver (lobules)
  • Brain (neurons)