Anatomy And Physiology Flashcards
Key Features Influenced by an Aquatic Lifestyle:
- locomotion
- thermoregulation
3. diving
4. osmoregulation
The marine environment:
- density - 800 times greater than air
- viscosity - 60 times greater than in air - pressure
- thermal conductivity - 24 times greater than in air 4. light attenuation
- high salinity/absence of freshwater
- changes in kidney
DRAG REDUCTION
- frictional/viscous drag
2. pressure drag
3. induced drag
4. wave drag
Frictional/Viscous Drag
• frictional drag of skin on water
• related to SA:V ratio (beneficial to have a low ratio)
• smooth skin - smooth boundary with fluid environment (see this in fully aquatic marine mammals)
• high turnover rate of outermost epidermal cells (some - once every 2 hours!)
Pressure Drag
• results from distribution of pressure around the body • dominating drag forces when swimming submerged
• fusiform shape - modification to reduce pressure drag
Induced Drag
• associated with water flow around flippers, fins, and flukes • act as hydrofoils - but formation of vortices around tips
Wave Drag
• occurs at surface ! bodies produce waves
• energy to move forward is minimized by wave
production
• total body drag - 4-5 times higher at surface
• negligible once animal is 3 body diameters below surface
BUOYANCY CONTROL
- increase quantity of materials that are less dense than water: air filled lung space (e.g. sea otter and manatee), fat/blubber
- reduce quantity of heavy materials - bone (density)
MOVEMENTS AND COSTS OF SWIMMING
Examples: otariids, phocids, cetaceans
• must produce propulsive forces equal to or greater than drag forces
• adaptations: enlarged propulsive structures + strong musculature, appendages
used as hydrofoils to produce thrust
• lack of recovery period during stroke cycle (unlike
Total Cost of Transport - COTTOT
- semi-aquatic mammals
- fully aquatic mammals
amount of energy required to move one unit of body mass a specific distance
- semi-aquatic mammals - 2-5 times higher than fully aquatic
- fully aquatic mammals - have similar values (and similar to terrestrial)
Thrust Production
• California sea lion
• cetaceans
• transmitting force from one place in body to
another!lever (i.e. a rigid structure that transmits force by rotating at a pivot point)
• California sea lion – muscles acting on brachium have large force-generating capacity + lever arm out is reduced
• cetaceans – axial muscles have large force- generating capacity + elongated neural spines + elongated transverse processes
Propulsive Efficiency
• ratio of span to chord
• high aspect ratio
• sea lion flipper
• sea otter feet
• cetacean flukes
• limb design that promotes efficiency is
one with long wingspan (length of wing from tip to base) and a short
maxilla
• manatee
• cetaceans
• floor of nasal canal and roof of
oral cavity
• manatee – most of maxilla lies
behind the orbit
• cetaceans – extensively
remodeled (
nasal cavity
• dorsal and central in skull
zygomatic arch
• cetaceans
• sirenians
• site of origin for masseter muscles
• cetaceans – reduced, especially in odontocetes
• sirenians – massive but porous, oil-filled (increases SA of attachment for the masseter)
occipital bone
• cetaceans
• articulates with the first cervical verterbra
(i.e. the atlas)
• spinal cord exits braincase through the occipital bone
• cetaceans – space in braincase between occipital bones and frontal bones is greatly reduced
III. THERMOREGULATION
- small SA:V ratio
- increased metabolic rate - activity and processing of food
- most have similar basal metabolic rates to terrestrial mammals
- however, will eat more and move around more when temps are low; still widely debated (proven in sea otters and neonates) - insulation
- counter-current heat exchanger
Insulation
- Hair
2. Blubber
- Hair
• traps air ! but gets compressed when wet and diving
• length and density – sea otter = 130,000 hairs/cm2 and fur seals = 60,000 hairs/cm2
• thick, primary hair surrounded by multiple underhairs (~ 1-10; sea otters = 50-100!)
• sebaceous glands – paired and associated with each hair; skin
Blubber
• thickened, adipose-rich hypodermis; energy store;
acts as a
must be able to dump excess heat
• thermal windows - areas with less fur and
less blubber
• blubber - highly vascularized!can vasoconstrict or vasodilate (depending on ambient temperature)
• … counter-current heat exchanger
Counter-Current Heat Exchanger
• arteries - move blood from heart (oxygen rich) to extremities; veins - move blood from extremities (oxygen poor) to heart
• lie on top of each other in extremities ! heat transferred from warm arterial blood to cool venous blood (cooled by external environment)
• so, when it
DIVING
A. Lung adaptations
B. Oxygen Stores/Consumption
C. Diving Physiology
Lung adaptations
• size - lung size (relative to body size) – not
significantly increased
• pressure – V of a given mass is inversely proportional to the pressure it is experiencing ! collapse (lungs and trachea) at depth (flexible rib cage and cartilage-enforced airways)
• nitrogen narcosis and the bends – avoidance (by forcing air into non-gas exchanging regions of lungs)
• female elephant seals – potential use as narcotic
Oxygen Stores/Consumption
• hypoxia!hypercapnia!accumulate by-products of anaerobic metabolism =
Diving Physiology
- breath holding - apnea
- bradycardia - reduction in heart rate
- peripheral vasoconstriction/selective ischemia - selective redistribution of blood
- diving hypometabolism
- Breath holding
- increased by ability to store oxygen in lungs, blood, and muscles
- not correlated to size overall but is correlated to size within groups (phocids, otariids, odontocetes, mysticetes)
- Bradycardia
- rapid, profound decrease in heart rate with submergence - maintained throughout dive, followed by tachycardia
- e.g. killer whale - 60 beats/min ! 30 beats/min (15+ sec); California sea lion - 150-250 beats/min!20-50 beats/min (1-3 mins)
- inverse relationship between heart rate and length of dive - e.g. grey seals - 119 beats/min ! 4 beats/min for dives
exceeding 15 mins - does not require diving – e.g. ringed seals resting underwater at breathing hole
Vasoconstriction/Selective Ischemia
• selective redistribution of blood to brain and heart
• marine mammal hearts – specialized to maintain blood pressure despite decline in heart rate (aortic bulb)
• explains, in part, how O2 is conserved during diving asphyxia
• sampling O2 in muscle myoglobin and blood hemoglobin!indicates circulatory isolation
• side-effect of moving blood away from locomotor muscles!build up of lactate (post-dive recovery period)
• adaptations: myoglobin, elevated mitrochondrial volume and density in these muscles, and altered aerobic enzyme capacities
• seal kidneys and liver experience ischemia ! incredible tolerance
Hypometabolism
• O2 available ≠ O2 required to sustain metabolic rates
• partially due to selective ischemia and reduced metabolism in non-
perfused organs
• episodic decline in metabolic rate !
Exercising Underwater:
• typically heart rate increases as function of exercise intensity
• doesn
VI. CARDIOVASCULAR SYSTEM
marine mammal CVS – 1. must deliver O2 selectively during breath holding and 2. must regulate the T of reproductive system
! relates to: a. arterial supply to brain b. AVAs
c. thermoregulation of reproductive structures
Arterial Supply to the Brain
• typical brain receives blood via internal carotid and vertebral arteries!enter cranial cavity and anastomose (
Arteriovenous Anastomoses (AVAs)
• vascular channels that connect an artery to a vein, near a capillary bed
• arterial blood that flows through an AVA bypasses capillaries and is rerouted
back toward heart before getting to terminal site
• associated with proximal vessels ! shunt arterial blood away from extremities
• e.g. flukes of a bndf – have AVA that are 2 mm in diameter!
• e.g. Weddell seals – said to play important role in selective ischemia
• also play a role in thermoregulation ! lie near surface of skin and if dilated can effectively transfer heat to environment
Thermoregulation - Reproductive System
• special thermoregulatory requirements of the reproductive system
• viable sperm production and storage – separation from body core (e.g. scrotum – otariids and polar bears)
• walrus and phocids – testes between blubber and abdominal muscles; cetaceans – deep in abdominal cavity
• phocids = testes enveloped in venous network that receives blood from surface (i.e. flipper)
• odontocetes – countercurrent heat exchanger!arterial and venous plexus (veins drain from dorsal fin and flukes)
• may relate to fetal temperatures as well
NERVOUS SYSTEM
• functions to detect changes in both internal and external environments of the animal
• CNS = central nervous system + PNS = peripheral nervous system CNS – brain and spinal cord
PNS – all other nervous tissues in body
• PNS - specialized neurons (receptors) transduce mechanical, thermal, chemical and electromagnetic signals into nervous signals!transmitted to CNS through sensory (afferent) nerves
• interneurons in CNS use incoming sensory info ! coordinate rapid and appropriate responses via signals sent through motor nerves (efferent) to effector organ
• LOOP
a. Cranial Nerves
• 12 pairs of cranial nerves connect the PNS with the brain – 3 sensory (I, II, and
VIII), 4 motor (III, IV, VI, XII) and 5 mixed (V, VII, IX, X, XI), and 13th (0 = closely
associated with olfactory nerve, I)
• size of nerve depicts higher conduction capacity and info transmission
I – olfactory and II – optic
! reduced in most
! increased in polar bears
VIII - vestibulocochlear nerve
! high-speed communication with brain
! odontocetes – 3-4 times more and largest axon diameters (conduction velocity)
V – trigeminal nerve
! mysticetes - largest cranial nerve ! pinnipeds – very large (vibrissae) ! manatees – massive (tactile mouths and vibrissae)
VII – facial nerve
!odontocetes – large (echolocation)
Neural Regulation of Diving Responses
RESPIRATORY SYSTEM
• air enters through nostrils and mouth ! pharynx
• from pharynx ! esophagus (food) or larynx (air)
• from larynx!trachea!bronchi (primary and secondary)!lobes of lungs
Isolation of Respiratory System from Aquatic Environment
• sea lions
• cetaceans
• larynx - protects respiratory system from food and fluids
• marine mammals must protect their respiratory system from water in their
environment
• sea lions - resting position of nares = closed
• cetaceans - nasal plugs seal entrance to nasal cavity when resting
• cetaceans - trachea and esophagus are morphologically separated by goosebeak!can eat and swim/breathe at the same time; no gag reflex
•
DIGESTIVE SYSTEM
- capture and manipulation of food – wide variety of feeding mechanisms and prey
- mechanical and chemical digestion
- nutrition
• mouth (ingestion)!processed (mastication)!swallowed!into pharynx! esophagus!stomach!small intestine!large intestine!gut & eliminated as feces
Stomach/Mechanical & Chemical Digestion:
pinnipeds
odontocetes
mysticetes
cetaceans
Intestines
DIGESTIVE SYSTEM
1. capture and manipulation of food – wide variety of feeding mechanisms and prey 2. mechanical and chemical digestion
3. nutrition
• mouth (ingestion)!processed (pinnipeds – single, highly distensible odontocetes – compartmentalized; forestomach
is highly distensible pouch of the esophagus
mysticetes – non-glandular forestomach with multiple compartments
!all cetaceans lack gall bladder sirenians – single, glandular stomach
Intestines – pinnipeds (long for carnivores), cetaceans (vary), and sirenians (very long!)
REPRODUCTIVE SYSTEM
Male Reproductive Structures
• form and function similar to terrestrial mammals
• testis-to-body-size ratio – varies but related to mating strategy (e.g. dusky dolphins = 8%, right whales = 2000 lbs)
• penis retracted into body wall (pinnipeds – vascular with baculum, sirenians – vascular w/o baculum, cetaceans – fibroelastic)
REPRODUCTIVE SYSTEM
Female Reproductive Structures:
• bicornuate uterus common to terrestrial mammals • ovaries paired and similar in structure, location and
shape
• placental type (varies – ancestral) – cetaceans = diffuse, sirenians – zonal, pinnipeds, polar bears and sea otters = zonal
OSMOREGULATION
Balance between water intake and excretion - maintenance of amount and electrolyte concentration of fluids in body
- eating and drinking balanced by removal of excess fluids and electrolytes (urine, feces, and evaporation)
- kidney - of marine mammals adapted to high salinity of seawater (and absence of freshwater)
Marine mammal kidney:
• larger
• 2 kidneys with multiple reniculi
• # of reniculi relates to level of marine exposure and diet
• cetaceans (450 reniculi), mysticetes (3000), otters and manatees (6-8)
• production of highly concentrated urine
• approx. 1/5 of cardiac output flows through kidney
Acquiring Water
- drinking freshwater
- via preformed and metabolic water in food
- fish and invertebrates ~ 60-80% water
- metabolic water derived from metabolism of food (fat, protein, and carbohydrates)
- fasting conditions (catabolize fat reserves, decrease urinary output, general minimization or lack of sweat glands) - mariposia - drinking saltwater - sea otters - highest
- documented in other species: northern fur seal = 300 ml/day, in cetaceans occurs during fasting but still low (800 ml/day in common dolphin), other values - incidental??
