Anatomy And Physiology

Question 0

Key Features Influenced by an Aquatic Lifestyle:

Answer 0

1. locomotion
2. thermoregulation

3. diving
4. osmoregulation

Question 1

The marine environment:

Answer 1

1. density - 800 times greater than air
   - viscosity - 60 times greater than in air
2. pressure
3. thermal conductivity - 24 times greater than in air 4. light attenuation
4. high salinity/absence of freshwater
   - changes in kidney

Question 2

DRAG REDUCTION

Answer 2

1. frictional/viscous drag

2. pressure drag
3. induced drag
4. wave drag

Question 3

Frictional/Viscous Drag

Answer 3

• 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!)

Question 4

Pressure Drag

Answer 4

• results from distribution of pressure around the body • dominating drag forces when swimming submerged
• fusiform shape - modification to reduce pressure drag

Question 5

Induced Drag

Answer 5

• associated with water flow around flippers, fins, and flukes • act as hydrofoils - but formation of vortices around tips

Question 6

Wave Drag

Answer 6

• 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

Question 7

BUOYANCY CONTROL

Answer 7

1. increase quantity of materials that are less dense than water: air filled lung space (e.g. sea otter and manatee), fat/blubber
2. reduce quantity of heavy materials - bone (density)

Question 8

MOVEMENTS AND COSTS OF SWIMMING
Examples: otariids, phocids, cetaceans

Answer 8

• 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

Question 9

Total Cost of Transport - COTTOT
- semi-aquatic mammals

- fully aquatic mammals

Answer 9

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)

Question 10

Thrust Production
• California sea lion
• cetaceans

Answer 10

• 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

Question 11

Propulsive Efficiency
• ratio of span to chord
• high aspect ratio
• sea lion flipper
• sea otter feet
• cetacean flukes

Answer 11

• limb design that promotes efficiency is
one with long wingspan (length of wing from tip to base) and a short

Question 12

maxilla
• manatee
• cetaceans

Answer 12

• floor of nasal canal and roof of
oral cavity
• manatee – most of maxilla lies
behind the orbit
• cetaceans – extensively
remodeled (

Question 13

nasal cavity

Answer 13

• dorsal and central in skull

Question 14

zygomatic arch
• cetaceans
• sirenians

Answer 14

• site of origin for masseter muscles
• cetaceans – reduced, especially in odontocetes
• sirenians – massive but porous, oil-filled (increases SA of attachment for the masseter)

Question 15

occipital bone
• cetaceans

Answer 15

• 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

Question 16

III. THERMOREGULATION

Answer 16

1. small SA:V ratio
2. 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)
3. insulation
4. counter-current heat exchanger

Question 17

Insulation

Answer 17

1. Hair

2. Blubber

Question 18

1. Hair

Answer 18

• 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

Question 19

Blubber

Answer 19

• thickened, adipose-rich hypodermis; energy store;
acts as a

Question 20

must be able to dump excess heat

Answer 20

• thermal windows - areas with less fur and
less blubber
• blubber - highly vascularized!can vasoconstrict or vasodilate (depending on ambient temperature)
• … counter-current heat exchanger

Question 21

Counter-Current Heat Exchanger

Answer 21

• 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

Question 22

DIVING

Answer 22

A. Lung adaptations
B. Oxygen Stores/Consumption
C. Diving Physiology

Question 23

Lung adaptations

Answer 23

• 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

Question 24

Oxygen Stores/Consumption

Answer 24

• hypoxia!hypercapnia!accumulate by-products of anaerobic metabolism =

Question 25

Diving Physiology

Answer 25

1. breath holding - apnea 2. bradycardia - reduction in heart rate 3. peripheral vasoconstriction/selective ischemia - selective redistribution of blood 4. diving hypometabolism

Question 26

1. Breath holding

Answer 26

- 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)

Question 27

2. Bradycardia

Answer 27

- 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

Question 28

Vasoconstriction/Selective Ischemia

Answer 28

• 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

Question 29

Hypometabolism

Answer 29

• 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 !

Question 30

Exercising Underwater:

Answer 30

• typically heart rate increases as function of exercise intensity • doesn

Question 31

VI. CARDIOVASCULAR SYSTEM

Answer 31

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

Question 32

Arterial Supply to the Brain

Answer 32

• typical brain receives blood via internal carotid and vertebral arteries!enter cranial cavity and anastomose (

Question 33

Arteriovenous Anastomoses (AVAs)

Answer 33

• 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

Question 34

Thermoregulation - Reproductive System

Answer 34

• 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

Question 35

NERVOUS SYSTEM

Answer 35

• 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

Question 36

a. Cranial Nerves

Answer 36

• 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)

Question 37

Neural Regulation of Diving Responses

Question 38

RESPIRATORY SYSTEM

Answer 38

• air enters through nostrils and mouth ! pharynx • from pharynx ! esophagus (food) or larynx (air) • from larynx!trachea!bronchi (primary and secondary)!lobes of lungs

Question 39

Isolation of Respiratory System from Aquatic Environment | • sea lions • cetaceans

Answer 39

• 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 •

Question 40

DIGESTIVE SYSTEM

Answer 40

1. capture and manipulation of food – wide variety of feeding mechanisms and prey 2. mechanical and chemical digestion 3. nutrition • mouth (ingestion)!processed (mastication)!swallowed!into pharynx! esophagus!stomach!small intestine!large intestine!gut & eliminated as feces

Question 41

Stomach/Mechanical & Chemical Digestion: pinnipeds | odontocetes mysticetes cetaceans Intestines

Answer 41

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!)

Question 42

REPRODUCTIVE SYSTEM Male Reproductive Structures

Answer 42

• 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)

Question 43

REPRODUCTIVE SYSTEM Female Reproductive Structures:

Answer 43

• 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

Question 44

OSMOREGULATION

Answer 44

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)

Question 45

Marine mammal kidney:

Answer 45

• 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

Question 46

Acquiring Water

Answer 46

1. drinking freshwater 2. 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) 3. 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??