Bio 205 Comparative Vertebrate Anatomy

Lecture 5 : The Body

Cellular anatomy

This picture illustrates a hypothetical animal cell with the major organelles. The structures that we are interested in are

  1. plasma membrane - a fluid, phospholipid membrane containing proteins that are used for transporting ions and small molecules, cell adhesion and movement, cell signalling, etc.
  2. cytopolasm - the fluid inside the cell (but outside the various organelles)
  3. nucleus - contains the DNA
  4. ribosomes - the site of protein synthesis. Ribosomes are a non-membranous structure made of RNA and numerous proteins
  5. Rough endoplasmic reticulum-Golgi-vesicles - this is the system designed for synthesizing and transporting proteins to the plasma membrane and the extracellular fluid. The proteins are synthesized on ribosomes associated with the ER. The proteins are modified in the ER, transported to the Golgi, then to vesicles, then to the plasma membrane (or beyond).
  6. mitochondria - these are the energy factories, that is, the organelle that synthesize ATP

Proteins

Many of the beautiful structure-function stories in comparative vertebrate anatomy are due to structural differences that span the hierarchy of anatomical organization, from the molecular to the whole organ and even whole animal level. At the molecular level, most of these differences are due to the shape and functional properties of proteins, so proteins will come up several times in this course, especially when we talk about the skeleton and muscle. Proteins have numerous functions include structural, movement, transport, and signalling. Proteins are synthesized in a multi-step process

  1. Transcription - A short segment of DNA (a gene) is copied (transcribed) into a mRNA molecule. Pieces (introns) of the transcript are removed. The remaining pieces (exons) are spliced back together to form the mRNA. This occurs in the nucleus
  2. Translation - the mRNA is transported to a ribosome in the cytoplasm. By converting (translating) the code in the mRNA, the ribosome synthesizes a protein - which is a string of covalently bound amino acids.

Proteins can be globular (like a ball of string) or filamentous (like a stretched string). Proteins can be made of a single or multiple subunits. E.g. myoglobin (single unit) vs. hemoglobin (four subunits).

Tissues

Cells are organized into higher level structures called tissues, of which there are four types:

  1. epithelium - cells are closely packed, often in distinct layers. The cell membranes of adjacent cells are often adhered to each other, which limits diffusion of ions/small molecules between cells. Epithelia covers the body, lines the gut and gut derivatives, lines the coelom, and covers the organs within the coelom, and lines the vessels.
  2. connective - cells are losely packed, often extremely so. The extracellular fluid outside the cells contains important structural proteins that give the tissue its mechanical properties. This is really important for understanding the skeletal system. Connective tissue includes the skeleton, including the deep layer of the skin, the structural components of many of the internal organs, and thin layers surrounding nerve and muscle cells.
  3. nervous - this includes the neurons and all of the cells that support the neurons.
  4. muscle - these are the contractile cells.

Organs

Organs are composed of multiple tissues. The major organs that interest us will be listed in the next level of design

Systems

The major functional systems of the body are composed of multiple organs. The class lectures and the textbook are organized by these systems. In general, an individual organ may function in more than one system.

  1. skeletal - the bones, cartilages, tendons, ligaments, and similar connective tissues of the body that function in
    1. protection - the skull, the rib cage, the skin
    2. support - the femur, the face
    3. energy transfer - tendons, skin
    4. energy storage and release - tendons, ligaments, skin
  2. skeletal muscle - the muscles used to move the different body parts
  3. nervous - the sensory organs, brains and nerves that control body functions via synapses
  4. endocrine - the many organs that control body functions via the secretion of blood-circulated molecules called hormones. Many, many cell types are involved in endocrine signalling but the major endocrine organs include
    1. hypothalamus
    2. pituitary gland
    3. thyroid gland
    4. adrenal gland
    5. pancreas
    6. gonads
    7. heart
    8. kidney
  5. Digestive - the gut and its derivatives involved in digestion and absorption of nutrients including
    1. mouth
    2. pharynx
    3. esophagus
    4. stomach
    5. small intestine
    6. large intestine
    7. colon
    8. appendix
    9. liver
    10. pancreas
  6. Respiratory - the organs necessary for gas exchange include (I'll save some surprises for later)
    1. mouth
    2. nasal cavity
    3. pharynx
    4. gills
    5. trachea
    6. lungs
  7. Circulatory - the organs necessary to transport oxygen, nutrients, metabolic wastes, metabolites, hormones, immune system proteins, etc.
    1. heart
    2. arteries
    3. capillaries
    4. veins
  8. Urinary - the organs used to balance water and ions and to excrete wastes
    1. kidney
    2. ureter
    3. bladder
    4. urethra
  9. Reproductive - the organs/structures used to make babies, including
    1. testes
    2. ovaries
    3. uterine tube
    4. uterus
    5. intromittant organ