Human Bio

• Lymphatic System


  An internal, non-specific defense of the body
• Lymphatic System


  Collects excess fluid that escapes the blood capillaries and returns it to the circulatory system
• Lymph


  Fluid that travels in lymph vessels; clear pale-yellow colour (plasma), does not circulate like blood – no pump → travels slowly
• Lymph vessels


  • Thin-walled, one-way, blind-ended vessels that lie in spaces between most tissues; travel at relatively low pressure + have valves (veins)
• Lymph vessels are more permeable than blood vessels, meaning that proteins and disease-causing microorganisms in the intercellular fluid can easily pass through the walls into the lymph
• Lymph Nodes


  Small bean-shaped structures that occur at intervals along lymph vessels – most numerous in neck, armpits, groin, and around alimentary canal
• Lymphatic System consists of

  • A network of lymph capillaries joined to lymph vessels
  • Lymph nodes
• Lymph entering a node

  Lymph is 'filtered' by the high concentrations of macrophages and lymphocytes found here
• Lymph passing through several nodes

  Before re-entering circulatory system
• Lymph nodes trapping large particles (i.e. bacteria)


  Which are destroyed by macrophages
• When infection occurs


  The formation of lymphocyte increases for a specific immune response → lymph nodes become sore + swollen
• Functions of the Skeleton (206 bones)

  • Support: gives shape and provides framework to support the weight of the body
  • Attachment: provides point of attachment for muscles + tendons
  • Movement: when these muscles contract, they allow movement
  • Protection: of vital body organs (e.g. brain is encased in cranium, ribcage protects heart + lungs)
  • Storage: minerals, salts and fats (e.g. C, P, Na, K)
  • RBC Production: in red bone marrow of spongy blood
• Red Bone Marrow (RBM)

  Contains blood stem cells; can differentiate into blood cells
• Divisions of the Skeleton

  • Axial Skeleton: Bones of skull – cranium, face and mandible
  • Vertebrae – cervical, thoracic, lumbar, sacrum, coccyx
  • Ribs + Sternum
  • Appendicular Skeleton: Upper limbs: Humerous, Ulna, Radius, Carpals, Metacarpals, Phalanges
  • Lower limbs: Femur, Patella, Tibia, Fibula, Tarsals, Metatarsals, Phalanges
  • Pectoral girdle (shoulder): Clavicle, Scapula
  • Pelvic girdle: Pelvis
• Types of Bone


  • Long: longer than they are wide
  • Short: cube-shaped
  • Flat: thin + flat, often curved
  • Irregular: complicated shapes
  • Sesamoid: embedded within a muscle/tendon
• Epiphyses


  Enlarged ends of a bone, compact ends of the outside surrounding spongy bone
• Diaphysis


  Main shaft of bone, hollow cylinder of compact bone surrounding a cavity
• Compact bone


  Outside 'border' of a bone, very dense + rigid, filled with tiny holes that hold blood vessels, protects spongy bone and bone marrow
• Spongy Bone (cancellous)


  On inside of compact bone, more porous than compact bone + has large spaces filled with marrow; RBM, where RBC production takes place (flat and long bones)
• Medullary Cavity


  Filled with yellow bone marrow – fat/lipid storage
• Periosteum


  Dense, white, fibrous, covering on outside of bone for strength; richly supplied with blood vessels and nerves
• Articular cartilage


  Covers each epiphysis for protection + cushioning
• Epiphyseal lines


  Bone growth areas in children
• Bone


  A CONNECTIVE TISSUE, cells are separated by large amounts of matrix; non-cellular material, inorganic salts are deposited in the matrix of bones; increasing strength and rigidity
• Osteon (Haversian System)


  Structural unit of a compact bone, run parallel to the long axis of the bone to give its strength
• Central canal


  Centre of each osteon, contains blood capillaries, nerves and lymph
• Lamellae


  Concentric layers of bony matrix which surround canal
• Lacunae


  Small spaces in the matrix between lamellae
• Canaliculi


  Tiny canals that run between Lacunae
• Osteocyte


  A bone cell which occupies each Lacunae; projections enter the canaliculi and make contact with other bone cells so materials can be passed from cell → cell
• Trabeculae


  Irregular, thin, bony plates; arranges spongy bone (not into osteon), lamellae not arranged in concentric layers → they are irregular, osteocytes still found in Lacunae, nerves and blood vessels pass through irregular spaces in the matrix
• Ossification: the process of forming bone


  1. Cartilage undergoes calcification through the deposition of calcium salts

  2. Cartilage cells die → replaced by osteoblasts – promoting more deposition of calcium salts

  3. Osteoblasts mature into osteocytes

  4. Bone formation continues until only a small band of cartilage remains

  5. Remnants of area this are known as epiphyseal lines, when the bone stops growing
• Osteoblasts


  Form bone by promoting deposition of calcium salts into matrix, absorbing calcium = lowing blood calcium levels
• Osteoclasts


  Reabsorb bone by secreting enzymes that dissolve the matrix, which release the stored materials, releases calcium into the bloodstream
• Balance between osteoblasts and osteoclasts

  • In living bone, osteoclasts constantly remove matrix, whilst osteoblast are always adding to it – this balance is very important
  • When osteoblasts deposit salts faster than osteoclasts remove then, the bone thickens, and bone density increases
  • When osteoclasts remove calcium salts faster than osteoblasts deposit them, the bone weakens → Osteoporosis
• Cartilage


  Made up of collagen (protein fibres) which are embedded in a protein-carbohydrate matrix, called Chondrin, provides structural support, whilst maintaining flexibility
• Locations of Cartilage


  • Surface of bones
  • Trachea
  • Bronchi
  • Forms of nose
  • Larynx
  • Outer ear
• Cartilage


  • Does not contain blood vessels, so all nutrition and waste removal occurs by diffusion through the matrix, slow → chondrocytes have slow metabolism and cell division, takes longer to heal, blood supply comes from blood vessels located in the inner layer of perichondrium: a fibrous membrane covering the external surface of cartilage, except where cartilage forms articular surface of a joint
• Chondroblasts


  Immature cartilage cells that are contained in the spaces in the matrix, they produce matrix and are gradually surrounded by it, until they are trapped → maturation = chondrocytes
• Types of Cartilage


  • Hyaline: many closely packed collagenous fibres; very fine, strong + flexible, found in rings of trachea + bronchi and articular cartilage (at ends of bones)
  • Elastic: elastic + collagenous fibres; not so closely packed, elasticity provides flexibility, found in external ear
  • Fibrocartilage: coarse appearance, parallel bundles of thick collagenous fibres, not compacted; slightly compressible – ideal for areas where body is not supported, found in intervertebral discs, meniscus of knee joint, and tissue joining two sides of pelvis