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Lecture 19

ZOO 2090 Lecture Notes - Lecture 19: Cool Air, Diphyodont, Acrodont


Department
Zoology
Course Code
ZOO 2090
Professor
Fred Laberge
Lecture
19

Page:
of 4
November 21 2011
Circulation Adptations
-Blood shunt in the skin
to disapate or keep it in the body
-heat conservation by counter-current exchange
-recycled heat is maintained close to body core, minimizing losses to
the environment
-between the blood and the vessel there is no gas exchange because
the walls are too thick but heat can go through
-exchanged with the blood that goes through the body
-temperature is much lower the blood that goes through the fin
-gradient of exchange is minimized at the tip of the fin
-heat exchange between the blood vessels
-temperature of the arteriolar blood and
-same principle can be used using a carotid rete and turbinate bones
to cool the brain
-cool air come into extensive contact with blood in the turbinate’s,
warming air before it gets to the lungs but also cooling blood that runs
through the nose
-this cool venous blood from the nose enters the carotid rete, where
vessels multiple and are organized in opposite direction to the
incoming carotid artery supplying the brain selective brain cooing
-might be involved in brain protection from heat stress or conservation
of body water during exertion
-saving water
Lecture 19. diversity in digestive, urinary and reproductive systems
Teeth
-derived from bony dermal armor
-composed of dentin, surmounted by a crown of enamel
-used to eat and/or for defense
Tooth Attachment
-Acrodont teeth attached to the outer air of the jawbone (most
fishes)
-Pleurodont attached to inner side (anurans, salamanders, many
lizards)
-thecodont teeth roots held in jawbone sockets( some fishes,
crocodilians, fossil birds, mammals)
Tooth Variation
-Homodont teeth all the same size and shape
-Heterodont teeth vary morphologically
Tooth Replacement
-Polyphodont teeth replace continuously throughout life
-Diphyodont-
Mammalian Teeth
-heterodont dentition with species-specific number of teeth evolved
along with ability to chew
-from front to rear:
Incisors (holding, cropping, or gnawing)
Canines (piercing flesh)
Premolars and molars cheek teeth (shearing and grinding)
Human formula: 2/2, 1/1, 2/2, 3/3 or 2-1-2-3(upper jaw –same as
lower)
-teeth of carnivores and herbivores are morphologically very different.
The jaw has a diastema if tooth types are missing
-flesh eater: their molars are designed to cut (blade like that go against
each other)
-herbivores: designed to grind (flatter surface)
Trends in Terrestrial Vertebrates
(see online)
Stomach
-better differentiated in tetrapods compared to fishes
1. Esophageal region only secretes mucus
2. Cardiac region (mammals only) only secretes mucus
3. Fundus secretes digestive enzymes and hydrochloric acid
4. Pyloric region secretes mucus
-conservative pattern amoung vertebrates, but some adaptations are
seen:
Non-glandular region can be used as temporary storage or
fermentation chamber
Gizzard of birds and crocodilians compensates for their lack of
grinding teeth
-part of the stomach where small rocks or grains of sand kept in the
gizzard are will participate in grinding food
-presents in the gizzard compensates for lack of grinding in teeth
Intestine
-major digestive and absorption site, with many glands
-a large surface area is essential, which is achieved by coils of the
canal, folds, villi, and microvilli of the internal surface
-in many tetrapods, there is differentiation into small and large
intestine
-small intestine is chief site of digestion and absorption of nutrients
-large intestine mostly recovers water, but can be used for
fermentation
-major digestive glands (liver, pancreas) empty
-herbivores have long guts with intestinal specializations that promote
fermentation (eg., caecum, large intestine, stomach) while carnivores
have shorter relatively unspecialized guts
Urine Production
-the kidney nephrons of amniotes have an elaborate system of tubles
that collect the primary urine produced by glomerular ultrafiltration
and transform it into urine to be excreted
-close association of blood vessels with kidney tubules creates a
counter-current urine concentration system
- urine is produced from blood
-capillaries pushes fluids out of the blood but keep the red blood
vessels in the blood
-comes into the tubules system of the kidney
-cells that can measure the urine content and adjust the blood flow
Kidney Variation
-urine is excreted into the cloaca of amphibians, reptiles, and birds
refluxed into the hindgut, which aids in the recovery of electrolytes and
water from the urine. Mammals have kidneys efficient at electrolyte
recovery and they excrete urine separately
Structure of mammalian Kidney
(picture online)
Nephron Variation
-long looped nephron (all the way to the base of the medulla)
-short looped nephron (only go to the out way)
-desert rodents tend to have mostly long loops of Henle. This helps
establish the strong concentration fradient in the medulla that is
needed to produce highly concentrated urine.
-aquatic mammals like the beaver, who have no need to produce
highly concentrated urine, show the opposite in that they have very
few long loops of Henle in their medulla
Urogenital System: Female Tetrapods
(picture online)
-ureter for urine, rectum and vagina separate, urethra and vagina
separate only in some species.