Mammalian Respiration & Circulation

Question 1

What are the challenges of respiration?

Answer 1

• oxygen exchange is slow
• even cells with low metabolism must be within 1-2mm of O2 source

Question 2

How have vertebrates evolved to overcome slow oxygen exchange?

Answer 2

• larger surface areas
• central cavities
• specialized respiratory systems
• respiratory and circulatory pumps

Question 3

Describe the mammalian nasal cavity

Answer 3

• modifies air before reaching lower respiratory passages
• warmed by mucosa
• humidified by serous nasal secretion
• cleansed by mucus gland secretion
• turbinate bones and cartilage

Question 4

Descibe turbinate bones and cartilage in mammalian nasal cavities

Answer 4

• covered by mucosal membrane - warms and cleans air
• adds element of moisture to air

Question 5

What is contained in the thoracic cavity?

Answer 5

• trachea
• lungs
• diaphragm
• heart
• all in bony thorax

Question 6

Give an overview of mammalian respiration

Answer 6

• occurs in lungs
• negative pressure breathing pulls air in
• diaphragm and intercostal muscles contract to expand cavity, air enters

Question 7

Which intercostal muscles contract for inhalation and exhalation?

Answer 7

external -> inhalation
internal -> exhalation

Question 8

Describe the lungs

Answer 8

• right lung bigger due to heart position
• lungs surrounded by membraneous pulmonary pleura

Question 9

Why are the lungs surrounded by membraneous pulmonary pleura?

Answer 9

reduces level of friction

Question 10

Describe the two lobes in the lungs

Answer 10

• right lung - anterior, middle, posterior and accessory lobes
• left - anterior, middle, only posterior lobes

Question 11

What is the order of branching within the lungs?

Answer 11

2 bronchi -> bronchioles -> alveoli

Question 12

Describe the relationship between respiration rate and body mass

Answer 12

exponential relationship between O2 consumption and mass of animal where the bigger the animal, the less oxygen consumed/g/hr

Question 13

Describe blood circulation

Answer 13

transport system for:
- O2 and CO2
- ions and metabolites: lipids, amino acids etc
- immune cells
- hormones/signals
- repair molecules and cells: fibrinogen, platelets
- removal of waste

Question 14

Describe the double circulatory system in mammals

Answer 14

• 2 circuits: pulmonary and systemic
• right and left atria & ventricles - 4 chambers
• right ventricle -> pulmonary artery
• left -> systemic aortic arch

Question 15

Describe the mammalian heart

Answer 15

• outer tough inelastic fibrous pericardium
• double-layered serous pericardium - serous fluid - lubrication

Question 16

Describe the evolution of tetrapod systemic arches

Answer 16

• anuran reptile: systemic arches of both sides persist
• bird: right systemic arch persists
• mammal: left systemic arch persists

Question 17

Describe how the neonate is ‘re-plumbed’ after the loss of the placenta:

Answer 17

• Neonatal lungs expand
  
  • Increased partial pressure -> ductus arteriosus closes
  • Fibrous tissue permeates ductus arteriosus -> becomes ligamentum arteriosum
  • More blood into left atrium closes foramen ovale between atria
  • Complete closure of atrial wall by 1 year
  • Pulmonary and systemic circulation separated
  • Ductus venosus liver shunt atrophies - ligamentum venosum
  • Hepatic circulation established
  • Umbilical vessels degenerate to fibrous tissue - lateral umbilical ligaments - ligamentum teres
    Placental circulation decreases

Question 18

What is a circulation challenge in marine mammals and how is it overcome?

Answer 18

• length of dive affected by oxygen stores and usage
• brachycardia from bpm to 30
• apnea - breath holding
• vasoconstriction: decreased flow to all organs except brain

Question 19

Describe hyperemia in digestion

Answer 19

• splanchnic circulation
• increased blood flow to specific tissues
• blood flow <30ml/min/100g at resting, 250 after meal

Question 20

Describe hyperemia in exercise

Answer 20

skeletal muscle blood flow decreases during exercise

Question 21

Describe hyperemia in thermoregulation

Answer 21

• many endotherms have differences in blood flow between body core and surface
• vasconstriction/dilation

Question 22

Describe the circulation system in hibernation

Answer 22

• state of metabolic depression particular to mammal species
• suppression of metabolic pathways
• decreased heart and breathing rates
• no urine of faecal excretion

Question 23

What are the states of hibernation?

Answer 23

• obligate: spontaneous and anually, enter regardless of temperature and food access
• faculative: only when cold-stressed, food-deprived or both

Question 24

Describe bear hibernation

Answer 24

• core temp drops ~4 degrees celcius
• suggested bears are thermoconforming and hibernation drived by environmental cues

Question 25

What physiological processes are in hibernation?

Answer 25

• lipolysis of adipose reserves
• periodic returns to normal body temp