cells, cavities, and homeostasis

tissues are a group of similar cells that work together to perform a specific function.

body cavities:

• anterior cavity

  • thoracic cavity: 2 pleural cavities (hold the lungs), and pericardial cavity (holds the heart)

  • abdominal cavity: digestive organs, kidneys.

• posterior cavity

  • cranial cavity: holds the brain

  • spinal cavity: contains the spinal cord

4 membranes and its functions:

• serous: lines and lubricates the internal cavities, reduces friction between organs.

• mucous: lines the airways, digestive tract, and reproductive tract.

• synovial: spaces in synovial joints

• cutaneous: outer covering (skin)

integumentary system:

• epidermis:

  • outer layer.

  • stratified squamous epithelial cells.

  • no blood vessels.

  • 2 major cells:

    • keratinocytes (produces keratin, waterproof cells)

    • melanocytes (produces melanin, dark pigment)

• dermis:

  • primarily dense connective tissues

  • fibres:

    • collagen fibres (strength) and elastic fibres (elasticity)

  • cells

    • fibroblasts (most abundant)

    • mast cells

    • white blood cells

    • fat cells

multicellular organism must maintain homeostasis

• negative feedback control system: any deviation from normal is detected and counteracted.

• components of the negative feedback control system:

  • controlled variable: any physical or chemical property that might vary and must be controlled to maintain homeostasis.

  • sensor (receptor): monitors current value for controlled variable and sends information to the control centre.

  • control centre: receives input from sensor, compares value to set point, signals the effector if necessary.

  • effector: takes action to correct the imbalance based on the information from the control centre.