8.0 Transport in Mammals Flashcards
mammalian circulatory / cardiovascular system
- includes blood vessels, blood, lymph & heart
- needed for: transport of nutrients and oxygen around the body, disposal of waste materials (co2, urea), transport of hormones, circulates WBC’s & RBC’s in body
CLOSED, DOUBLE CIRCULATORY SYSTEM:
- closed: blood is contained in blood vessels, always in heart, arteries, veins or capillaries
- double: blood passes through the heart twice, in one complete circuit
TYPES OF CIRCULATION SYSTEMS:
- pulmonary circulation: circulation through lungs & heart, much lower blood pressure, no harm to delicate lung tissue
- systemic circulation: circulation through other parts of the body and heart excluding the lungs
- higher blood pressure
- more effective to transport oxygenated blood to all parts of the body
Pulmonary Artery
GENERAL:
➤ Carry blood away form the heart
➤ Carry oxygenated blood (except for pulmonary artery)
STRUCTURE:
- thick walls
- narrow lumen (in relation to thickness of walls)
- 3 layers: Tunica intima (endothelium), Tunica media, Tunica externa
Tunica intima (endothelium):
- squamous epithelial cells = flattened epithelial cells
- single layer, one-cell thick
- smooth surface facing lumen
- MINIMIZES FRICTION with moving blood
Tunica media:
- thickest layer
- collagen fibres
- elastic fibers
- smooth muscle cells
Tunica externa:
- collagen fibers
- elastic fibers
- ONLY
FUNCTION:
collagen fibers:
- withstands high pressure
- prevents rupture of vessels
elastic fibers:
- allows vessel to stretch to withstand high pressure
- to maintain blood pressure / smooths out pulsatile flow
- when blood enters at lower pressure it recoils to give the blood a small push to increase blood pressure
smooth muscles:
- maintains blood pressure
- contracts and relaxes to maintain pulse flow (contract and stretch)
- keeps blood moving forward / maintains blood flow
Arteries to Arterioles
- arteries further from heart have less elastic fibers and more smooth muscles
ELASTIC ARTERIES:
➤ Closer to the heart
➤ Elastic fibers can stretch / recoil to withstand high pressure and smooth out pulsatile flow
MUSCULAR ARTIERIES/ARTERIOLES:
➤ Further from the heart
➤ Smooth muscles can contract / relax to control volume of blood flow
➤ Become narrower so blood flow slows down
Pulmonary Vein
GENERAL:
- returns blood to heart
- carries deoxygenated blood (except for pulmonary vein)
- low blood pressure
- slower blood flow than in artery
- 3 layers
STRUCTURE RELATED TO FUNCTION:
- irregular / flattened oval shape
- wide lumen in relation to thickness of wall
- small lumen : short distance for diffusion
- thin tunica media: less elastic tissue and smooth muscle
- presence of valves: prevents backflow of blood, ensures blood flows towards heart, valves close the pathway when blood
- surrounded by skeletal muscles: when skeletal muscle contracts, pushes blood towards heart
Capillaries
GENERAL:
- brings blood close to tissues
- links arteries to veins
- 7 micrometres
STRUCTURE RELATED TO FUNCTION:
- made of squamous epithelial cells
- one-cell thick: short diffusion distance
- has pores / gaps between endothelial cells: allows some smaller components of blood to pass through (e.g. water, ion, glucose)
Arterioles to Venules
ARTERIOLES:
- small muscular arteries
- smaller diameter with greater proportion of smooth muscles
VENULES:
- larger vessels formed by joined capillaries, as blood leaves a capillary bed
Structure differences of blood vessels
ARTERIES:
VEINS:
CAPILLARIES:
WBC’s & RBC’s
RBC’s:
- short lived (120 days)
Structure related to Function:
1) small and flexible
➤ Diameter about 6-8μm
➤ Able to squeeze through capillaries (7μm)
➤ Reduce diffusion distance
2) Bioconcave Disc
➤ Increases surface area
➤ For diffusion of oxygen to cells
3) No nucleus, no mitochondria, no ER
➤ More room for haemoglobin
➤ Maximize the number of oxygen carried by RBC
LYMPHOCYTES:
- B-lymphocytes: mature in bone marrow, produces antibodies
- T-lymphocytes: mature in thymus, does NOT produce antibodies
Structure:
➤ Smaller than phagocytes
➤ Large round nucleus
➤ Little cytoplasm
Function:
➤ Involved in specific immune responses
➤ Responds to only specific non-self antigens
➤ Mature lymphocytes circulate in the blood and lymph
➤ Accumulate at sites of infection
NEUTROPHILS:
Structure:
- multi-lobed nucleus
- have receptor proteins on its membrane
- used to identify non-self pathogens
Function:
- when there is an infection, large numbers are released from bone marrow
- acccumulates at site of infection
- short-lived (few hours)
- dies after digesting pathogens
MONOCYTES/MACROPHAGES:
- monocytes mature into macrophages
Structure:
➤ Lobed nucleus / kidney-bean shaped
➤ Larger than neutrophils
➤ Have receptor proteins on its membrane
➤ To identify pathogens as non-self
Function:
➤ Monocytes: circulate in blood
➤ Mature into macrophages when it leaves blood and enter organs
➤ Long-lived cells
➤ Macrophages found in organs such as liver, lungs, spleen, kidney, lymph nodes
WBC’s VS RBC’s
1) Contains nucleus
2) Mostly larger than erythrocytes (except for
lymphocytes)
3) Spherical / irregular in shape: Do not have a biconcave disc shape
4) Phagocytes have granular cytoplasm
Tissue Fluid
BLOOD PLASMA:
* Plasma: a pale yellow liquid
* Blood plasma is mostly water, with a variety of substances dissolved in it. (glucose, urea, plasma protein)
GENERAL:
➤ Aka interstitial fluid
➤ Bathes cells
➤ Medium for exchange of materials between cells and blood
➤ Formed from blood plasma
FORMATION PROCESS:
➤ Due to differences in blood pressure at arterial and venous ends
➤ Blood pressure in arterioles is higher than blood pressure in venules
➤ Blood plasma flows out into tissue spaces
➤ Through endothelial pores of capillaries
➤ But gaps are small, large plasma proteins cannot pass through
Tissue fluid contains:
➤ Water,gases,glucose,fattyacids,urea,ions
➤ Smaller proteins (e.g.antibodies)
➤ Overall lower protein concentration than plasma
➤ Some WBCs (e.g.phagocytes)
➤ Lower oxygen concentration than plasma
➤ NO platelets
➤ NO large proteins
➤ NO RBCs
RETURN OF TISSUE FLUID TO BLOOD:
➤ Blood pressure at venous end is lower than at arterial end
➤ Solutes concentration is higher in the blood plasma of capillary due to large, dissolved
proteins
➤ So at venous end, some tissue fluid returns to the blood
➤ 90% is returned to blood, through endothelial gaps
➤ 10% moves into lymphaTc vessels and becomes lymph
➤ Lymph is returned to blood via the subclavian veins near heart
LYMPH:
➤ Lymphatics
➤ Tiny, blind-ending vessels
➤ Valves
➤ Allow the tissue fluid to flow in but stop it from leaking out
➤ Wide enough to allow large protein molecules to pass through
➤ Lymph nodes
➤ Small, lymph-filtering organs
➤ Filled by white blood cells, function in defense
➤ Become swollen and tender when in an infection ➤ Assistant with cancer spread
the Role of Water in the Circulatory System
SOLVENT ACTION:
HIGH SPECIFIC HEAT CAPACITY:
Role of RBC’s in Gas exchange
PROCESS:
1. CO2 diffuses from respiring Tssue –> plasma –> RBC
2. Carbonic anhydrase in cytoplasm of RBC converts CO2 of carbonic acid* This maintains a steep concentration gradient for diffusion of carbon dioxide from Tissues to blood
3. Carbonic acid dissociates into hydrogencarbonate ions and hydrogen ions * Decrease in pH
4. Hydrogencarbonate ions diffuse from RBCs to plasma * Cl- move into RBCs to balance the charges / maintain electrical neutrality (chloride shift)* An anion exchange protein embedded in the membranes of red blood cells
5. H+combines with Hb to form haemoglobinic acid (HHb) * Hb has higher affinity for H+ than oxygen * H+ lowers affinity of Hb for oxygen * HHb also prevents pH from decreasing / acts as buffer
6. Hb releases oxygen * Oxygen diffuses from RBC blood plasma respiring cells
HAEMOGLOBIN:
➤ A globular protein found in RBCs
➤ Has quaternary structure
➤ Made of 4 polypepTde chains
➤ Each polypepTde has a haem group
➤ Each heam group contains 1 iron ion (Fe2+)
➤ Each Fe2+ can combine reversibly with 1 oxygen
molecule, forming oxyhaemoglobin
➤ One Hb molecule can combine with 4 oxygen molecules (8 atoms)
➤ Hb + 4O2 –> HbO8
CARBONIC ANHYDRASE:
* Speeds up the reaction
* Maintains CO2 concentration gradient
* If CO2 simply transported in plasmaàdecrease blood pH
* Acts as a buffer
HAEMOGLOBONIC ACID FORMATION:
5. H+combines with Hb to form haemoglobinic acid (HHb) * Hb has higher affinity for H+ than oxygen
* H+ lowers affinity of Hb for oxygen
* HHb also prevents pH from decreasing / acts as buffer
Chloride Shift
PROCESS:
1. Carbon Dioxide Transport:
* CO₂ diffuses from tissues into red blood cells (RBCs).
* Inside RBCs, CO₂ reacts with water, forming carbonic acid (H₂CO₃) through the action of the enzyme carbonic anhydrase.
* Carbonic acid dissociates into hydrogen ions (H⁺) and bicarbonate ions (HCO₃⁻).
2. Bicarbonate Ion Exchange:
* To prevent the accumulation of bicarbonate ions in the RBCs, HCO₃⁻ diffuses out of the red blood cell into the plasma.
* To maintain electrical neutrality, chloride ions (Cl⁻) from the plasma move into the RBC to replace the negatively charged bicarbonate ions. This movement of chloride ions into the RBCs is known as the chloride shift.
3. Buffering Effect:
* The H⁺ ions that are produced from carbonic acid are buffered by hemoglobin, preventing the red blood cell from becoming too acidic.
IMPORTANCE:
- occurs in red blood cells to maintain electrical neutrality during the transport of carbon dioxide (CO₂) in the blood
CO2 transportation
➤ 85% of CO2 is only transported in the form of hydrogencarbonate ions
➤ 85% hydrogencarbonate ions
➤ 5% dissolve in blood plasma
➤ Remained as CO2 molecules
➤ 10% carbaminohaemoglobin
➤ diffuse into RBC
➤ Bind to terminal amine of Hb
➤ Form carbaminohaemoglobin (different with carboxyhaemoglobin)
Oxygen Dissociation Curve of mature haemoglobin
PROCESS:
➤As partial pressure of oxygen (pO2) increases, percentage saturation of haemoglobin with O2 increases
➤ At capillaries in lungs:
➤ O2 supply is high, so pO2 is high
➤ Hb is highly saturated with O2
➤ At respiring tissues: O2 demand high for aerobic respiration, so pO2 is low
➤ Hb releases O2,Hb is less saturated with O2
➤ S-shaped curve
WHY S CURVED?:
➤ Haemoglobin exhibits cooperative binding / allosteric effects, as oxygen binding increases the affinity of haemoglobin for more oxygen.
➤ At low pO2 (respiring tissue)
➤ 1st O2 combine with haem group
➤ Hb changes shape
➤ At increasing pO2
➤ Binding of 2nd and 3rd O2 is easier than the 1st
➤ Small increase in pO2, results in large increase in % saturation
➤ At high pO2 (lungs)
➤ All haem groups are getting fully occupied
➤ Hb fully saturated
➤ Curve levels off
IMPORTANCE:
➤ pO2 in lungs are higher
➤ pO2 in respiring tissues are lower
➤ As blood travel from capillaries in lungs to tissues:
➤ Small decrease in partial pressure leads to a large decrease in % saturation
➤ Allows more oxygen to be released / dissociate from Hb
➤ Affinity of Hb to oxygen decreases at low pO2
➤ pO2 in lungs are higher
➤ pO2 in respiring tissues are lower
➤ As blood travel from capillaries in lungs to tissues:
➤ Small decrease in partial pressure leads to a large decrease in % saturation
➤ Allows more oxygen to be released / dissociate from Hb
➤ Affinity of Hb to oxygen decreases at low pO2
Structure of Heart
Cardiac Cycle
GENERAL:
➤ A typical resting heart rate: ~72 beats per minute (bpm)
➤ Average length of one complete cardiac cycle is 0.8s
➤ Systole = contraction / pumping
➤ Diastole = relaxation / filling
PROCESS:
1) Atrial systole: atria contracts, ventricles relax, atrioventricular valves open, atrial pressure > ventricular pressure, pressure in arteries is high but slowly decreasing as blood flows to entire body, blood flows from atria to venticle
2) Ventricular systole: ventricles contract, atria relax, semilunar valves open, atrial pressure < ventricular pressure, pressure in arteries is high and rapidly increasing as blood is pumped through aorta, blood flows from ventricles to aorta and pulmonary artery
3) Diastole: atria and ventricle relax, vena cava pulmonary veins atrioventricular valves open, pressure in chambers are low but increasing as blood fills heart, pressure in arteries > ventricular pressure slowly decreasing as blood flows to entire body, blood flows from vena cava & pulmonary veins to atria and trickles into ventricles
BLOOD PRESSURE:
➤ Changes with stage of cardiac cycle
➤ Usually measure the pressure on the left Side of heart: left atrium, left ventricle, aorta
➤ Due to higher pressure and larger difference in pressure compared to right side
Generally:
➤ Atrial pressure is relatively low because it has thinner walls and exert less force
➤ Atrial pressure increases during atrial systole
➤ Ventricular pressure increases during ventricular systole
➤ Aortic pressure increases during ventricular systole
import: systole, diastole, activity of valves, blood pressure
Importance of SAN, AVN, Purkyne tissue in Cardiac Cycle
GENERAL:
➤ Cardiac muscles are myogenic
➤ Myogenic=contraction initiated by muscle itself, not by nervous impulses from outside
➤ How is the cardiac cycle initiated and coordinated?
➤ Wave of excitation/electrical impulse is passed through the:
➤ 1) Sinoatrial node (SAN)
➤ 2) Atrioventricular node (AVN)
➤ 3) Purkyne tissue
PROCESS:
1. SAN:
➤ Determines rhythm of heart
➤ Also called pacemaker
➤ Found at the wall of the right atrium
1. SAN / pacemaker sends out waves of excitation / electrical impulses
2. Impulses spreads across atria
➤ Both atria contract simultaneously
➤ Result in atrial systole
➤ But non-conducting tissue prevents impulses from reaching the ventricles
➤ So atria and ventricles do not contract at the same time
➤ Wave of excitation passed to AVN
2. AVN:
➤ AVN is situated at the base the right atrium
➤ Prevents atria and ventricles from contracting at the same time
➤ Acts as a relay station
3. There is a time delay of ~0.1-0.2 seconds
➤ Allows atria to empty
➤ And ventricles to fill
4. AVN sends wave of excitation to ventricles
➤ Wave of excitation passed to Purkyne tissue
3. Purkyne tissue:
➤ Tiny bundles of conducting fibers
➤ Found at base of ventricles
5. Purkyne Tssue conducts excitation to base of septum / ventricles
6. Electrical impulses spread upwards in ventricle walls
➤ Ventricle muscles contract frombase upwards
4. Refractory period:
➤ Period of insensitivity to stimulation
➤ ~0.4 seconds
➤ Atrial and ventricular muscles relax
➤ Diastole
