Lect 10 Flashcards
Sauropsida and Synapsida
Within Amniota
Saurosipda: all living reptiles, synonymous with reptila
Synapsida: all living mammals
Divisions of Amniota
• Sauropsida and Synapsida diverged during Carboniferous
(Before major mass extinction)
• Sauropsida includes all living birds, lizards, and crocodiles
• Synapsida includes all living mammals
• Many extinct lineages within each clade throughout history but will ignore for this course
Amp are amniotes
Mammals much less diverse than reptiles
Most diverse tetrapod clade is the birds
Respiration
Ancestral muscle functions
• Costal (ribs) ventilation – axial (between ribs) muscles expand volume of thoracic cavity
- Symmetrical (expanded on both sides at same time) or bilateral (expand sides at diff times more common due to lateral undulation walking long gets compressed when walking sometimes air wold get transported to the other lung instead of going back out the body, air could become stale)
• Axial muscles also flexed the body laterally for locomotion
- Asymmetrical or uniateral
(Inhibits breathing when running hence insurance is very low)
Respiration
Separating limb and breathing movement
As become more derived muscles with limbs and lungs separated from trunk
• Limbs move under body, powered by different muscles
To
• Posterior ribs reduced (of trunk)
(Also see reduced protection of organs there, increases flexibility of back/spine, impacts how hind limb can move too)
Which
• Allows for dorsoventral trunk flexion (front to back)
(Lung scomprressed symmetrically, forces air in and out, better for longer endurance)
Respiration
Synapsid lungs
• Lungs are expandible (“compliant”) (expand and contract)
• Air flow is tidal or bidirectional
- Traces the same path in and out
- Some “old” air retained each breath (not enough to be problematic)
• Alveoli are the site of gas exchange (are sacs, increase surface area and need to be kept moist, associated with blood vessels)
- Alveolar lungs
Respiration
Sauropsid lungs
• Lungs are rigid and structured not complient
• Air flow is unidirectional inside lungs
- One-way movement always
- Bidirectional in bronchi (movement picks up again), trachea
• Faveoli are the site of gas exchange
- Faveolar lungs
Birds —> air sacs
Crocs —> trachea and/or bronchi
Respiration
Ventilation
Synapsids
• Diaphragm (under rib cage): muscular sheet separating pleural (where lungs are) and abdominal cavities
- Contraction increases volume of pleural cavity, drawing air in (contract, sa increases, increases volume, air comes in, relax, sa decreases, volume decreases, air goes out)
Sauropsids
• Multiple modes of increasing volume of pleural cavity
• Movement of viscera (organs)
• Movement of muscles
• Movement of gastralia (belly ribs) (aren’t connected to spine, could be connected to pelvic or pectoral girdle or soft tissue connections)
Circulation
Reduction in pharyngeal arch vessels
• Basal amniote: (sim to tetrapod) (ventricle may or may not be separated)
- Most of the blood vessels (going to head) associated with pharyngeal arches are lost during development
- Two sets remain to supply head and body
(Blood vessels going to gills have been lost, however, some retain like carotid artery, then one going to back of body)
• Birds and mammals
- Body loop becomes asymmetrical through loss of one side
Circulation
Bird and mammal hearts
Typically heart same, 4 chambers
Convergently seen
Deox > right vent passed to right atrium to lungs for gas exchange
Ox blood returned to left atrium goes to Left vent to be sent to rest of body
Left vent very strong with its pushing
Circulation
Lizard and turtle hearts
Atrial contraction
• Deoxygenated blood from right atrium enters the ventricle
• Crosses muscular ridge to cavum pulmonale
• Oxygenated blood from left atrium enters cavum arteriosum of ventricle
• Open valve keeps blood separated
• Muscular ridge isolates blood to go to lungs
Ventricular contraction
• Deoxygenated blood pumped to lungs
• Valve closes and intraventricular canal opens to allow pumping of oxygenated blood to aortae
• Muscular ridge prevents oxygenated blood from going to lungs
Circulation
Crocodile hearts
Typical blood flow – high blood pressure
Aorta drains each thing, little passage way depends on blood pressure. When high coming out of left vent, it opens up and will overwhelm ox blood coming from right
Blood flow when basking – low blood pressure
Less pressure from left vent, More deox blood from right, more mixture of blood when not active
Excretion
Nitrogen-based waste products
• Metabolism produces waste ammonia, which is toxic
- Some ammonia excreted as-is
• Ammonia can be converted into urea, which is less toxic
- Urea can be concentrated into urine (no water, store in bladder) by reabsorbing water
- Synapsid kidney very efficient at producing urine
• Ammonia can be converted into uric acid, which is less toxic - Combines with other ions to precipitate a salt
- Uric acid is the primary excretory waste of sauropsids (percolates as a salt —> hence bird poop white)
Excretion
Nephrons
• Nephron: Basic structural unit of the vertebrate kidney
• Glomerulus: filters blood
• Long tube for chemical manipulation of the filtrate
• Tube forms loop of Henle in mammals
From glomerculus, elongated for more surface area, more ion pumps, more area for water control
More efficient for water retaining
Removes ion and things need 1st then as go through tube may absorb or pet stuff back in
Excretion
Synapsid urine production (simplified)
• Glomerulus produces concentrated filtrate
• Blood vessels surround the loop of Henle
• Ions are manipulated along the length of the tube to create osmotic gradient
• Allows for water to re-enter blood passively
• Compounds necessary for body function selectively reabsorbed
• Toxins are isolated in filtrate (to be excreted)
Excretion
Sauropsid uric acid production
• Sauropsids can excrete some ammonia and urea
• Sauropsid kidneys produce dilute urine, but uric acid is not very soluble in water
• In the bladder or cloaca, the uric acid (mainly excreting) combines with other ions and precipitates out of solution
- Water is reabsorbed (not as much tho)
Not extended loop of henle
