Summary: Vertebrate Structure And Function

Read the summary and the most important questions on Vertebrate Structure and Function

• 2 Practical Morphology

• 2.1 Lamprey

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• What are some differences between the hagfish and the lamprey?

  Blood, cerebellum, eyes, cranium, pinneal eye, lateral line system, labyrinth, nasopharyngeal pouch, cartilageounous vertebrae, accessory heart, gill pouches, kidneys, connection between lumen of pericard and coeloom, sex

• Which elements of the lamprey are ancestral and which ones are derived? (think also about the characteristics fitting a parasitic lifestyle).

  Ancestral characteristics (symplesiomorf): 2 semi-circular ducts, no jaws, nasopharyngeal pouch, no
  paired fins, a simple nervous system, 7 gill arches, no vertebrae (rudimentary), products of the gonads
  (e.g. eggs, sperm) are released into the coeloom (no duct)
  Charactersitics fitting a parasitic life style: poorly differentiated digestive tract, rasping tongue, mouth
  that functions as a suction cup

• Which function does the pharynx have in Ammocoetes larva and in the adult lamprey (is this function homologous/analogous)?Which function does the endostyle have in Ammocoetes larva and in the adult lamprey (is this function homologous/analogous)?

  The pharynx of Ammacoetes is an intermediate between the primary and secundary function of the
  pharynx (also see Haikouella).
  Primary function and morphology: filterfeeding, endostyl and epibranchial groove
  Secondary function and morphology: muscles support a pump function and the gill arches are
  covered with respiratory epithelium
  The pharynx of the lamprey mainly serves the respiration function (via the gills) and transportation of food
  (past the velum, to the oesophagus). The endostyl has now metamorphosed into thyroid tissue
  (endocrine gland)

• Could you conclude that there is a secondary classification in the lamprey brain?

  
  
  The brains of the lamprey are intermediate between the primary and secundairy classification, since the
  rhombencephalon is not yet clearly divided into a metencephalon (cerebellum) and a myelencephalon
  (medulla oblongata).
  When dissecting the animal, it is hard to recognize a cerebellum.

• 3 Practical Histology

• 3.2 Lower GI

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• Which regions of the GI tract are these?

  1. Oesofagus
  2. stomach
  3. duodenum
  4. jejunum
  5. ilium
  6. rectum  

• Macroscopically there is little difference between jejunum and ileum. What are thedifferences on a microscopic level?

  
  
  in the jejunum, the density of the villi is higher, to create a larger surface
  available for the absorption of nutrients. A typical characteristic of the ileum is that it
  contains GALT tissue (gut associated lymphatic tissue)

• How is the large surface area of the intestine realized? (human intestinal surface isthe size of a tennis court)

  
  
  folds projecting inwards, into the lumen of the intestine (valves of
  Kerckring), villi and microvilli

• Where in the GI tract can you find sphincters, and why?

  sphincters promote unidirectional flow in the intestine and allow
  compartments to have their own ‘ecosystem’ (conditions in that compartment, such
  as pH). You find sphincters between the oesophagus and the stomach (cardia),
  between stomach and duodenum (pylorus), between ileum and colon (ileocecal
  sphincter) and at the end of the GI- tract (anus)

• There should not be any leaking between the enterocytes. Which intercellularconnections prevent this? What other types of intercellular connections are present?

  Tight-junctions prevent leakage between cells. Desmosomes and adherens
  junctions interconnect enterocytes to become an intestinal epithelium

• Why is there a lot of attention paid to the immune system in the intestine, and whyfor the lower GI tract specifically?

  Because the lumen of the GI-tract is basically ‘the outside world’ (and thus
  potentially a threat to the body).
  Gastric acid kills a lot of potential pathogens: the upper part of the GI-tract benefits
  from this. However, the further away from the stomach, the bigger the risk becomes
  again. That is why more GALT is located in the lower GI-tract specifically.