Lecture 2: Diving 2 Flashcards
What are the 4 adaptions that aquatic animals (cetaceans) have for deep diving?
- Flexible thorax (chest)
- Large distensible veins, venous sinuses, rete mirabile
- Large Lungs
- Resilient trachea (windpipe) and bronchi
Explain what happens when a cetacean dives deep (anatomically)?
as pressure increases during a dive, the lungs are compressed to collapsing point, and air escapes into rigid air spaces (bronchi and trachea)
What is the role of lungs for cetaceans during a dive (how do they work: 3)?
Provides stretch on inspiration (sponge-like rubber band)
They almost completely empty lungs using elastic recoil of
inflated lungs and diaphragm
On expiration, allow lungs to become atelectatic without
pulling from the thoracic wall
What does atelectatic mean?
collapsed alveoli (collapsed lung)
What is the function of Alveoli?
The site of gas exchange in the lungs
What is the general comparison between the lung mass as a percent of body mass of a terrestrial mammal vs a Phocoenidae?
Terrestrial Mammals is around 1% while Phocoenidae is around 3%
What is apnea in cetaceans?
– temporary cessation of breathing during dive
What does explosive ventilation in cetaceans do?
allows for greater total lung
volume exchange
What is the role of the distensible veins, venous sinuses and rete mirabile in a cetacean?
They are larger and Fill with blood as respiratory air is compressed during a dive and as the thorax (chest) collapses
“At the same time, blood squeezed out of the thorax is mostly shifted to the huge rete mirabiles of the vertebral column and spinal cord, from where originate the vertebral vessels that supply the brain”
What is the Rete Mirabilia?
a networks of arteriovenous shunts in the head and thorax
What does the Rete Mirabilia do for cetaceans?
Store blood while diving
Fill space in head and thorax as air is compressed during a dive
How do larger lungs affect cetaceans ability to dive compared to humans?
“Dolphins can replace as much as 95 percent of the air in their lungs in a single breath” “For comparison, humans are capable of replacing only as much as 65 percent”
What are chuffs?
When dolphins breath really hard
What is the comparison of dolphins vs humans moving air?
Dolphins move air two to three times faster than humans could
What is the role of a resilient trachea (windpipe) and bronchi (airways) for cetaceans (3)?
Allow lower respiratory passages to collapse
Cartilage lines trachea and upper airway (stiff)
Dead space (no gas exchange), holds air during dive
What the common name from trachea?
windpipe
What is the common name for bronchi?
airway
Overall, what do the 4 adaptations that cetaceans have do for them when diving to avoid the bends?
Allows air to be compressed away from alveoli in the lungs during increased pressure during a dive. It also prevents gas exchange and nitrogen from entering blood
Describe a marine mammals heart rate normally and during a dive.
A cardiac respiratory arrhythmia is normally present. The heart rate increases on inspiration and decreases with apnea/breath hold. It will decrease and remain constant whether breath hold is 20 seconds or a few minutes. constantly fluctuates between
upper and lower values (typical HR: 79 - 103 bpm) with
breathing
What is bradycardia?
Slow heart rate
What animals have the most profound bradycardia?
Seals; 4 bpm
Describe bradycardia in cetaceans compared to seals, and what is another name for it?
not as intense as seals. Also called “dive reflex”
What is the dive reflex in humans like and what happens anatomically?
occurs in people in response to water submersion, can be used for treatment:
“people hold breath, face in water, develop bradycardia,
apnea and redistribute blood to vital organs while limiting O2
consumption in non-essential muscle groups
What is the medical significance of respiratory rates in cetaceans?
Under anesthesia, a cetacean or pinniped (e.g. sea lion, seal) will not have the normal cardiac respiratory arrhythmia. They will often develop a dive response under anesthesia which can lead to hypoxemia
Bradycardia (slow HR)
Apnea (breath holding)
What does hypoxic mean?
low oxygen
How do you get a patient out of hypoxia?
give oxygen
What are the cardiovascular adjustments cetaceans have?
- Greater blood volume
- Increased PCV and hemoglobin (protein
molecule in red blood cells that carries O2) - Smaller Red Blood Cell (RBC) size
What is hemoglobin?
protein molecule in red blood cells that carries O2
What is the comparison on cetaceans blood volume vs humans?
Up to 2-3x more blood per unit
body weight than humans
What does smaller RBC do to help cetaceans?
Helps resist effects of vascular stasis and “the bends”
Describe seals RBC.
high deformability
Describe the shape of RBC.
doughnut-shaped with larger periphery
What are the 4 main component of blood?
Plasma, RBC, WBC, Platelets
What is plasma made of?
Water, proteins, etc
What do RBC do?
Carry oxygen
What do WBC do?
Fight infection
What are WBC also known as?
Buffy coat
What do platelets do?
Help clotting
What does Muscle Myoglobin do?
Stores/supplies O2 to muscle cells (myocytes); 50% of total O2 storage capacity in many marine mammals
What is one of the MAJOR diving adaptations of marine mammals?
Muscle Myoglobin
What does Muscle Myoglobin physically change about the appearance of marine mammals?
Makes their muscle tissue very dark (so dark red it looks black)
What is Muscle Myoglobin?
protein in striated muscle that binds O2
What are myocytes?
Muscle cells
Is myoglobin present in land mammals?
yes but in smaller amounts
one more slide to understand
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