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Comparative Anatomy And Physiology Of Animals > Circulation And Blood > Flashcards

Circulation And Blood Flashcards

1
Q

Cnidarians eg jellyfish

A

multi-cellular and relatively complex but rely on diffusion for gas exchange and flagella circulate digestion products around the coelenteric fluid to allow cells to directly phagocytose food particles

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2
Q

Platyhelminthes eg flatworms

A

Flat so short diffusion distances so can rely on diffusion

In large turbellaria diffusion distances are increased so they have gut ceca in which cilia move digestion products nearer the edges of the body

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3
Q

Nematodes

A

small (most < 2.5 mm long) and do not need a circulatory system

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4
Q

Annelida worms

A

Large and segmented
Require a circulatory system
Each segment has a coelom filled with fluid which is circulated by cilia on the internal walls and by muscular contractions

developed a haemal system where there are blood vessels and hearts that allow fluid transport around the body.

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5
Q

Blood vessel definition

A

A tubular structure carrying blood through the tissues and organs I.e. vein, artery or capillary

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6
Q

Heart definition

A

A muscular organ in most animals, which pumps blood through the blood vessels of the circulatory system

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7
Q

Blood definition

A

A body fluid in animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away

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8
Q

Haemolymph definition

A

A body fluid that is a mixture of blood and interstitial fluid

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9
Q

Annelida circulatory system

A

Dorsal and ventral blood vessels located in mesentery
Blood (containing haemoglobin) flows anteriorly in the dorsal vessel and posteriorly in the ventral vessel

In each segment blood moves from the ventral vessel to the dorsal vessel via a capillary plexus in the body wall and vice versa through vessels around the gut wall – ‘closed’ system

Walls of blood vessels (esp. dorsal) are contractile and pump blood via peristalsis

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10
Q

Mollusca circulatory system

A

Open system Increased size and body plan complexity mean that molluscs have a well developed circulatory system
Heart with pairs of atria and a medial ventricle
Dorsal aorta
Blood vessels
Haemolymph (blood)
Haemocoel – body cavity filled with haemolymph

Heart has one or more pairs of atria – receive oxygenated blood from gills
Empty into medial ventricle, which is continuous with aorta, which branches to smaller vessels to deliver blood to haemocoelic sinuses in the head, foot and bathe the visceral mass
Blood passes over the nephridia and returns to heart by afferent branchial vessels

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11
Q

Mollusca closed circulatory system

A

Cephalopods (octopus, squid, cuttlefish) are advanced invertebrates in a variety of ways. Their circulation is characterized by being a ‘closed’ system where blood is kept within vessels and there are hearts either side of the gills. Blood from the two gills flows to the systemic heart which pumps it around the body. After perfusing the systemic tissues the de-oxygenated blood is returned to two branchial hearts – one per gill. These hearts force the blood through the gills and beyond.

This system shows that blood can be pumped around in different states of oxygenation. Oxygen rich is forced from the gills by the branchial hearts pumping blood into the gill capillaries. The systemic heart then pumps this oxygenated blood to the rest of the body, where the tissues use the oxygen. Deoxygenated blood is then moving to the branchial hearts as the systemic heart beats. In effect, there is a pumping system to the respiratory organs and one for the rest of the body.

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12
Q

3 different hearts in cephalopods

A

One per gill (brachial hearts) x2
One systemic heart

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13
Q

Molluscan circulation

A

Molluscs have simple hearts that can only produce low differential pressure
One heart wouldn’t be enough to distribute blood through both the tissues and gills capillaries network so secondary hearts improve efficiency

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14
Q

Arthropoda- insecta

A

Insects have one dorsal blood vessel (‘heart’) that pumps haemolymph from the posterior to the anterior into the aorta

Haemolymph empties directly into haemocoel and returns to the heart directly via holes, ‘ostia’, in the vessel walls
Very simple system but only transports nutrients and waste products, NOT respiratory gases

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15
Q

Arthropoda- insects

A

Insects have one dorsal blood vessel (‘heart’) that pumps haemolymph from the posterior to the anterior into the aorta

Haemolymph empties directly into haemocoel and returns to the heart directly via holes, ‘ostia’, in the vessel walls
Very simple system but only transports nutrients and waste products, NOT respiratory gases

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16
Q

Arthropoda - crustacea

A

Crustaceans respire via gills and large species need more complex circulatory systems to transport respiratory gases
Blood pumped into haemocoel but infrabranchial sinus collects blood and haemolymph and delivers it to gills

An infrabranchial sinus collects haemolymph and the pumping action of the heart draws haemolymph through the gills and the branchio-pericardial ‘veins’ deliver it to the pericardial sinus.

Collecting vessels from gills deliver haemolymph into a pericardial sinus
Haemolymph enters heart via several ostia and is pumped out via arteries

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17
Q

Cephalochordata- amphioxus

A

Well developed haemal system but no compact heart
Ventral sinus venosus and aorta are contractile
Contractions push blood through gill capillaries to paired dorsal aorta
Colourless blood

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18
Q

Vertebrate hearts

A

Blood flows through tubular vessels
2nd Law of Thermodynamics predicts that fluid moving along a vessel will stop unless energy is expended
Circulatory systems require a pump, very often a heart, to keep blood moving

Need to an efficient heart increases as animals increase in size
Blood vessels are defined in terms of their relationship to the heart
Arteries carry blood away from a heart
Veins carry blood to a heart

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19
Q

Teleost (bony fish) heart

A

Heart has four sequential chambers
Blood delivered by the great veins enter the sinous venosus and then the atrium
Ventricle is the main propulsive chamber
Bulbus arteriosus has elastic properties to help maintain blood pressure
In sharks, it is contractile and is called the conus arteriosus
Passive valves between the chambers ensure that blood flows in the one direction

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20
Q

Conus arteriosus

A

Sharks
Contractile to maintain blood pressure

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21
Q

Cardiac system in teleosts

A

Heart receives deoxygenated blood from systemic tissue which is pumped to the gills via the ventral aorta
Dorsal aorta distributes oxygenated blood to the tissues via the dorsal aorta

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22
Q

Limitations of the teleost heart

A

Vertebrate circulation has two parts
Respiratory circulation
Systemic circulation
Single cycle circuit – blood goes to respiratory system first
Heart virtually empty after each systole (contraction phase)
Blood goes through capillaries in the gills and loses pressure
Systemic circulation is under low blood pressure

Heart receives de-oxygenated blood from the systemic tissues
Pumping is energy intensive so requires a lot of oxygen
In many fish blood perfusing the spongy myocardium, which comprises the ventricle, has a limited oxygen supply
Some species have some compact myocardium, which has its own coronary blood supply that delivers oxygenated blood

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23
Q

Spongy myocardium

A

lots of vessels to supply blood but this limits the amount of muscle.

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24
Q

Compact myocardium

A

coronary blood vessel mean that the myocardium can increase its muscle content and so generate more thrust during a contraction.

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25
Q

Amphibian cardiac system

A

Three-chambered heart and double cycle circuit
Separate atria – left receives oxygenated blood and right de-oxygenated blood
Single ventricle receives output from both atria (lacks septum)
Cardiac output from the ventricle can go to the lungs and/or skin- partially oxygenated blood——in practice differential contraction of the two sides of the ventricle wall, in conjunction with the septa, mean that the vast majority of the oxygenated blood goes to the body and deoxygenated blood goes to the lungs.

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26
Q

Crocodilians

A

Ventricle is completely divided into two chambers by a septum allows for differential pressure between ventricles
Two systemic arteries – one from each ventricle
Left and right aortas connected shortly after leaving heart - Foramen of Panizza
Also there is a anastomsis further away from heart

27
Q

Crocodilians cardiac system

A

Air-breathing – blood can leave right ventricle easily and go the lungs.
Systolic pressure is low and does not open the flap into the systemic aorta

Diving – blood flow is restricted when leaving right ventricle so systolic pressure is increased and opens the flap into the systemic aorta

28
Q

Cardiac systems in birds and mammals

A

Complete separation of the two ventricles
Double cycle circuit – completely independent systemic (high pressure) and pulmonary (low pressure) circuits
Improved respiratory gas exchange = higher metabolism and more active life style

29
Q

Selective distribution

A

Generally deoxygenated blood sent to the lungs and oxygenated blood sent to the systemic tissues using anatomical features that physically block the mixing of blood
In amphibians and non-Archosaurs an effective double cycle circuit can be established despite anatomy suggesting otherwise – unclear how this is achieved
Crocodilians exhibit the variability in the system

30
Q

Maintenance of different blood pressures in systemic and pulmonary circuits

A

Systemic circuits are longer and more complex so drops in blood pressure are likely – need high pressures be maintained to produce high flow rates
Such high pressures in the lung capillaries would induce ultrafiltration of plasma through vessel wall and the lungs would fill with fluid
Pulmonary circuits require lower blood pressures

31
Q

Redistribution of cardiac output

A

Being able to adjust the flow of blood to the lungs can be advantageous if you have a low metabolism and breathe intermittently
A turtle during a dive will not be breathing air so having an incomplete septum in the ventricle means that blood can be diverted around the systemic system rather than go to the oxygen-depleted lungs
Amphibians – lungs get blood by having lower pressure in blood vessels— path of least resistance

32
Q

Comparison between vertebrates

A

Metabolic rates vary between vertebrates with endo thermic species having higher metabolic rates
Trend towards increased heart mass with fish having the smallest hearts relative to body mass

33
Q

Which group of organisms has a three-chambered heart?

A

Amphibians

34
Q

In annelids, which blood vessel carries blood towards the head?

A

Dorsal vessel

35
Q

How does blood enter the crustacean heart?

A

Haemolymph enters heart via several ostia

36
Q

In terms of their circulation, how do cephalopods differ from other molluscs?

A

Closed system rather than open system

37
Q

Which one of these is the odd one out, and why? Blackbirds, squirrels, or turtles

A

Turtle - has a ventricle chamber that has three parts that allows some mixing of oxygenated and deoxygenated blood. two atria but one ventricle that is incompletely divided into three chambers by horizontal and vertical septa

Blackbird/squirrel- 2 atria and 2 ventricles

38
Q

The heart as a pump

A

Heart creates circulation by causing a pressure difference
A periodic muscle contraction increases pressure inside the heart and forces blood out of the lumen
Contraction phase = systole
Relaxation phase = diastole

39
Q

Why is blood forced out of the heart under pressure

A

Blood, being water-based, is resistant to compression and so is forced out of the heart under pressure.

40
Q

What does atrial and ventricular systole cause

A

Increase in blood pressure in the atrium lumen
Reduction in lumen volume causing blood to flow out under pressure into the ventricle
Back flow is prevented by valves in the veins delivering blood or in the heart

41
Q

Myogenic

A

Rhythmic depolarisation originating in muscle

42
Q

Neurogenic

A

Depolarisation that originates in neurones

43
Q

Where is a neurogenic heart found

A

Lobsters
Spiders

44
Q

Neurogenic heart

A

rhythmic depolarisation originates in neurones, e.g. lobster (Homarus), other crustacean and arachnids
Each muscle cell in heart is innervated and only contracts when stimulated by nerve impulses

Heart has cardiac ganglion – nine neuronal processes have direct nervous connection with each muscle cell
One posterior neuron assumes role of pacemaker – spontaneous periodic train of action potentials that stimulate other neurones and in turn muscle cells

45
Q

Myogenic heart

A

Adjacent muscle cells are electrically coupled so depolarisation of one cell rapidly leads to direct depolarisation of adjacent cells
Cells will spontaneously contract but not in unison
Requires pacemaker
Fish, amphibians and non-avian reptiles – located in sinus venosus or at its junction with the atrium
Birds and mammals – located in wall of right atrium
Modified muscle cells with reduced contractile apparatus but first to spontaneously depolarise
Depolarisation spreads across myocardium via conduction

46
Q

Where is the pacemaker located in a birds/mammals myogenic heart

A

Wall of right atrium

47
Q

Where is pacemaker of myogenic heart in fish/amphibians/non-avian reptiles

A

Sinus venosus or at its junction with the atrium

48
Q

Path of depolarisation in myogenic heart

A

depolarization starts in the S-A node in the right atrium wall. And spreads across the atrium wall causing the atrial systole (contraction). However, the tissue between the atria and ventricles is fibrous and not conductive. The two parts of the heart are connected by the Purkinje fibres that are in the atrioventricular bundle that allow the depolarization to cross the non-conductive barrier. The atrial depolarization causes depolarization of the A-V node, which depolarizes the Purkinje fibres which then depolarize the muscle cells in the ventricle wall. This system means that blood in the atria are pushed into the ventricular chambers before the ventricles contract.

49
Q

Micro capillary beds

A

Arterial blood delivered via arterioles
Capillary walls consist only of vascular endothelial cells so wall is <1μm thick
1 cm³ of skeletal muscle can have 10-20 metres of capillaries
Blood leaves via venules
Leads to reduction blood pressure

50
Q

Blood flow through vessels

A

Rates of blood flow depend on differences in pressure and vascular resistance
Consider non-turbulent flow of water through a horizontal, rigid-walled tube

51
Q

Factors affecting the rate of blood flow

A

Pressure at the entry to the tube and pressure at the exit
Radius of the lumen
Tube length
Viscosity of the liquid

Hagen-Poiseuille equation describes the inter-relationships between these variables

52
Q

Flow rate

A

Increasing the pressure difference increases the rate of the flow
Increasing viscosity reduces flow rate
Flow rate is a function of r4/l so it is very sensitive to changes in radius of the lumen

Friction between the liquid and the wall of the tube slows the rate of flow
Energy ‘lost’ as heat
Liquid in the middle of the tube flows faster

53
Q

Vasoconstriction that reduces the lumen radius by ½ reduces blood flow by

A

1/16

54
Q

Vascular resistance

A

Flow rate = ΔP/R, where ΔP = difference in blood pressure at start and end of vessel
Flow rate will increase if ΔP increases but will decrease if R increases

Blood vessels are not uniform in radius and although total cross-sectional area increases in a capillary bed, the radius of each vessel is very much reduced
Increased R in capillaries leads to slower rates of blood flow
Vascular resistance is proportional to the fourth power of the radius of the vessel lumen
When blood moves into a capillary bed its volume remains the same but lumen radius decreases slowing flow rate and increasing vascular pressure

55
Q

Leaky capillary walls

A

Capillary walls are leaky – gaps between cells and aquaporin protein channels
As blood enters a capillary plasma is forced out
Some is reabsorbed by osmosis as blood leaves the capillary

56
Q

Starling-Landis hypothesis

A

there is a net loss of liquid as blood passes through a capillary bed

57
Q

How is plasma returned to the circulatory system

A

by the lymph system
Body movement and muscular contractions move lymph through vessels

58
Q

Gravity and blood pressure

A

A liquid in a tube exhibits differences in pressure according to height because gravity is pulling the liquid down
Above a heart arterial pressure drops and vice versa
Human heart can only generate enough pressure (12.7 kPa) to pump blood 1.2 m above itself

59
Q

Gravity, blood pressure and lower limbs

A

Blood has a mass and in the venous system blood pressure is low
Gravity could lead to blood pooling in parts of the body below the heart
Contractions of skeletal musculature help force blood through veins, which contain valves that prevent blood from going back down the vessel

60
Q

Gravity, blood pressure and giraffe

A

Selective vasodilation / vasoconstriction helps distribute blood to parts of the body where needed most and relieve pressure on heart

Vasoconstriction in lower limbs redirects blood to the head
Large left ventricle and high aortic pressure (29 kPa vs. 13 kPa in other mammals)

Vasodilation in lower limbs redirects blood to the legs

61
Q

Heart rate and body size

A

Heart rate (beats per minute) in mammals exhibit a negative relationship with body mass – small mammals have fast heart rates and big mammals have slow heart rates

62
Q

Control of heart rate

A

Hormonal – epinephrine and norepinephrine increase heart rate and volume
Neural – all hearts have regulatory neurones that stimulate or inhibit the heart rate
Intrinsic controls – Frank-Starling mechanism suggest that stretching of the cardiac muscle tends to increase the force of contraction
Balances venous return with cardiac output

63
Q

Cardiac output

A

Cardiac output (mL/min) = heart rate (beats per min) x stroke volume (mL)

64
Q

Rate of O2 delivery

A

Rate of O2 delivery = cardiac output x (arterial [O2] – venous [O2])

Comparative Anatomy And Physiology Of Animals (10 decks)

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