CVR 1: Cardiovascular Flashcards
What are the four main functions of blood?
Transport of nutrients, waste products, and hormones around the body.
Regulation of temp, pH, water balance.
Immunity (white blood cells & antibodies).
Clotting.
What is the base of the heart?
Superior surface of the heart, formed mainly of the left atrium.
When do the coronary arteries fill with blood?
During diastole.
What is the mediastinum?
The thoracic cavity excluding the lungs (but includes the trachea).
In what compartment of the mediastinum would you find the aortic arch?
Superior compartment of the mediastinum.
Which compartment of the mediastinum contains the thymus?
Trick question! Thymus is across two compartments: the superior and the anterior inferior compartment.
What would you find inside the middle inferior compartment of the mediastinum?
Th heart inside the pericardial sac, the pulmonary trunk, and the ascending aorta.
What blood vessel do the coronary arteries originate from?
Ascending aorta.
What blood vessels does the brachiocephalic trunk of the aortic arch bifurcate into?
Right common carotid (right side of the head & neck).
Right subclavian (right upper limb).
One branch of the aortic arch is the brachiocephalic trunk. Name the other branches.
Left common carotid (left side of the head & neck).
Left subclavian (left upper limb).
Why are the aortic bodies important?
They contain chemoreceptors monitoring arterial O2 and CO2, visceral sensory information sent to CNS via vagus nerve -> reflex responses which regulate ventilation.
Where does the descending aorta lead to?
The thoracic and then abdominal aorta, supplying blood to lower body.
What connects the pulmonary trunk to the aortic arch?
Ligamentum arteriosum (fibrous, cord-like connection), remnant of ductus arteriosus.
What veins converge to form the superior vena cava?
left & right internal jugular and subclavian veins join to form left & right brachiocephalic veins. These two veins converge to become the superior vena cava.
Where does the trachea originate and terminate?
From the larynx in the midline of the neck to the sternal angle, where it bifurcates into left and right main bronchi (the carina).
Where is the trachea palpable?
Superior to the suprasternal notch.
Where does the oesophagus originate and terminate?
Originates from the pharynx and terminates at the stomach.
Is the oesophagus anterior or posterior to the trachea?
Posterior.
How do the phrenic nerves enter the thorax?
Descend through the neck and enter via the superior thoracic aperture.
Why are the phrenic nerves important for respiration?
Innervate the diaphragm and pericardium.
From what spinal nerves do the phrenic nerves originate from?
C3, C4, C5 (“keep the diaphragm alive”).
Where do the vagus nerves originate?
Brainstem.
Describe the structure of the pericardium.
Two layers:
Tough outer fibrous layer attached superiorly to the great vessels, and inferiorly to the diaphragm. Innervated by phrenic nerves.
Thin inner serous layer; parietal and visceral layers which are continuous with each other, pericardial fluid between them in the pericardial cavity.
What is another name for the inferior surface of the heart?
The diaphragmatic surface.
What part of the heart forms the apex and where is the apex palpable?
The left ventricle forms the apex.
The apex beat is palpable at the left 5th intercostal space, in the midclavicular line.
What are the ear-like appendages/outpouchings of the walls of the atria called?
Auricles.
What causes pericardial effusion?
Fluid in pericardial space from e.g. pericarditis or trauma.
Why can severe and rapid pericardial effusion cause cardiac tamponade?
Fibrous layer of the pericardium cannot stretch, so heart is compressed and unable to fill properly.
What nerves do the recurrent laryngeal nerves originate from?
Vagus nerves - recurrent laryngeal nerves ascend back up the neck to the larynx.
Why might lung cancer cause a hoarse voice?
Cancer at apex of lung may involve the recurrent laryngeal nerves, leading to paralysis of the ipsilateral intrinsic laryngeal muscles, so cannot fully adduct vocal cords.
You examine a patient and note they have pitting oedema of their ankles. Blood tests show that their blood albumin level is low. Describe the relationship between albumin and oedema.
A low albumin causes a decrease in oncotic pressure and water diffuses from the blood into the interstitial fluid
A healthy student drinks 2 litres of water in 5 mins. Describe the physiological response.
The excess fluid causes a decrease in blood osmolality (osmolarity) which in turn causes a reduction / stopping of Anti Diuretic Hormone release. The kidneys therefore excrete more water leading to increased urine volume.
Renin is a proteolytic enzyme.
What is the principal site of renin production?
Juxtaglomerular cells
Anti-diuretic hormone (ADH) acts on the kidneys to promote water retention.
What is the site of synthesis of ADH (antidiuretic hormone)?
Synthesised by the supraoptic and paraventricular nuclei of the hypothalamus.
However it is then stored in the posterior pituitary gland.
Renin is a proteolytic enzyme
What is the key action of renin in the renin-angiotensin-aldosterone system (RAAS)?
Renin is a proteolytic enzyme which activates angiotensinogen to produce angiotensin I.
Where is aldosterone synthesised, what is it, and what is its main function in the renin-angiotensin-aldosterone system?
Steroid hormone released from the adrenal cortex in response to stimulation by angiotensin II.
It promotes sodium reabsorption and potassium secretion in the distal tubules of the kidneys.
Explain the difference between sensible and insensible fluid loss.
Insensible fluid loss is loss that is not easily measured e.g. sweating, water lost from respiration, evaporation during abdominal surgery.
Sensible fluid loss is that which is easily measured e.g. urine output, vomit, fluid in surgical drains.
Where do the coronary arteries originate from and what are they called?
The aortic root. Right coronary artery and left main stem.
How many pairs of ribs are there and which vertebra do they attach to?
12 pairs, each pair attaching to a thoracic vertebra (of which there are 12!).
Where is the xiphisternum?
Inferior end of sternum
What are the three sets of intercostal muscles and which are for inspiration/expiration?
External = for inspiration.
Internal & innermost = for expiration.
Where is the mitral valve and how many leaflets/cusps does it have?
In between the left atrium and left ventricle. Two cusps/leaflets.
Where does the phrenic nerve originate from?
C3, C4, C5
“C3, 4, 5 keep the diaphragm alive”
Innervates diaphragm and pericardium.
Where does the vagus nerve originate from?
Cranial nerve X (10th cranial nerve).
How many lobes does each lung have?
Right lung = 3 lobes.
Left lung = 2 lobes.
True or false: Each lobe of the lung has its own air, blood, and nerve supply.
True!
Which pleura is closer to the lung tissue, parietal or visceral?
Visceral pleura.
(Think visceral feeling!)
What is the buffy coat?
When blood is put in a centrifuge, the buffy coat is the very small layer in between the haematocrit and the plasma, containing platelets and neutrophils.
What component of the blood causes oncotic pressure?
Albumin (a protein).
What is the difference between osmotic and oncotic pressure?
Osmotic pressure is the force driving water from low concentration of solutes to high concentration.
Oncotic pressure is specifically the osmotic pressure generated by large molecules in the blood (mainly albumin), also known as colloid osmotic pressure.
What are Starling forces?
The forces involved in the movement of water between capillaries and interstitial fluid.
Hydrostatic, osmotic, and oncotic pressure.
What is the function of plasma in relation to temperature?
Plasma acts as a heat sink to stabilise overall body temperature. Moves excess heat from “hot” organs e.g. liver and muscle, and circulates to extremities.
How do proteins buffer hydrogen ions in the plasma?
Amino acid side chains bond to H+ in acidic conditions, acting as a base, to attempt to return to neutral pH.
In alkaline conditions, amino acid acts as an acid and releases H+.
What is complement?
A specialised series of proteins that contribute towards the inflammatory response, main goal is to kill pathogens and deal with rogue proteins. Also called the complement system or the complement cascade.
What are the three pathways in the complement system?
Classical pathway.
Alternative pathway.
Lectin pathway (initiated by specific sugars on the surface of microbes)
Why does the alternative pathway in complement cascade occur faster than the classical pathway?
It takes time for WBCs to create antibodies, which the classical pathway requires for activation. Where as the alternative pathway is activated directly by pathogens or damaged cells.
What is the term for when complement coats pathogens to enhance their recognition and ingestion by phagocytes?
Opsonisation.
What are the main four functions of complement?
Opsonisation.
Lysis.
Inflammation (attracting immune cells to site).
Clearance of immune complexes.
What part of complement forms the membrane attack complex?
MAC, C5b to 9
Where are plasma proteins such as albumin, complement, and clotting factors produced?
In the liver.
What is haemostasis?
A normal physiological response to bleeding, involves activation of the coagulation cascade and formation of the platelet plug.
What are the three pathways of the coagulation cascade?
Intrinsic, extrinsic, and common.
What is the coagulation cascade?
Series of proteolytic enzymatic reactions that lead to the formation of a blood clot by converting soluble fibrinogen into insoluble fibrin.
How is the intrinsic pathway of the coagulation cascade triggered?
Damage to the vascular endothelium exposes collagen, which activates factor XII, starting cascade.
XII -> XIIa -> XI -> XIa -> IX
IX and VIIIa then both activate factor X in common pathway.
How is the extrinsic pathway of the coagulation cascade triggered?
External trauma causing blood to escape from vessel, Tissue Factor (TF) released from damaged tissue. TF combines with Factor VIIa, activating Factor X in common pathway.
Which coagulation cascade pathway is faster, intrinsic or extrinsic?
Extrinsic pathway is faster.
What is the convergent point for both intrinsic and extrinsic pathways in the coagulation cascade?
Factor X - the start of the common pathway.
What are the key steps of the common pathway of the coagulation cascade?
- Activated factor X + factor Va converts prothrombin (factor II) to thrombin (factor IIa).
- Thrombin converts fibrinogen (factor I) to fibrin.
- Fibrin forms a mesh that strengthens platelet plug.
- Thrombin also activates factor XIII which cross-links fibrin to form a stable clot.
What regulates the coagulation cascade?
Antithrombin III
Protein C and Protein S
Tissue Factor Pathway Inhibitor (TFPI).
How does antithrombin III affect the coagulation cascade?
Inhibits thrombin and Factors IXa, Xa, XIa, and XIIa.
What inactivates Factors Va and VIIIa to slow down coagulation cascade?
Protein C and Protein S
Does Tissue Factor Pathway Inhibitor (TFPI) inhibit the extrinsic or intrinsic pathways of the coagulation cascade?
Extrinsic - blocks Tissue Factor VIIa complex.
What is fibrinolysis?
Breakdown of fibrin by a cascade of proteolytic enzymes.
What are the key components in fibrinolysis?
Plasminogen, tissue plasminogen activator, plasmin (a fibrinolytic protease).
What is another term for platelets?
Thrombocytes.
How are platelets derived?
From megakaryocytes in the bone marrow, which produce multiple platelets from one megakaryocyte. Platelets are small, anucleate cell fragments.
How long to platelets live for?
7-10 days.
What are the key functions of platelets?
- Form platelet plug to stop bleeding.
- Release chemicals to attract other platelets and clotting factors.
- Clot stabilisation - work with fibrin.
- Release growth factors for wound healing.
- Trigger inflammation - recruit and activate leucocytes, release pro-inflammatory mediators.
How are platelets activated?
Damage to blood vessel endothelium exposes collagen.
Platelets stick to exposed collagen and release chemical signals (e.g. ADP, thromboxane) that activate more platelets.
How do platelets form a plug (platelet aggregation)?
When platelets are activated e.g. by collagen, they change shape from smooth discoid to spiky stellate. Stick to each other like velcro, and bond together chemically.
Which protein in plasma is essential for blood clotting?
Fibrinogen.
Which component in plasma is most responsible for maintaining oncotic pressure?
Albumin
What is the primary role of complement proteins in plasma?
Coating pathogens to enhance phagocytosis.
What triggers the intrinsic pathway of the coagulation cascade?
Damage to the blood vessel’s endothelium, exposing collagen.
What percentage of blood volume is erythrocytes (haematocrit)?
45%
Why to erythrocytes have a biconcave shape?
To increase the surface area for gaseous exchange.
What is the diameter of an erythrocyte?
10 mircometres
Why do erythrocytes have a finite life?
No nucleus (to make more space for haemoglobin) so can’t repair itself.
Where are erythrocytes produced?
In the bone marrow.
What is the Bohr shift?
On the oxygen affinity curve, shift to the right meaning reduced affinity for O2 of haemoglobin, means more O2 is passed onto tissues and occurs in conditions when there is higher demand for O2 e.g. raised temperature.
How is 2,3-DPG produced?
Produced by erythrocytes during glycolysis, in the Lubering-Rapoport Pathway.
How is 2,3-diphosphoglycerate different to 2,3-biphosphoglycerate?
They’re the same thing!
2,3-DPG and 2,3-BPG are the same thing.
When is production of 2,3-DPG increased and why is this important?
Increased by factors associated with increased tissue O2 demand e.g. hypoxia, anaemia, low pH.
Important because 2,3-DPG reduces the affinity of haemoglobin for O2, so promotes release from RBCs into tissues.
What has a higher affinity for O2, myoglobin (Mb) or foetal haemoglobin (HbF)?
Myoglobin in muscle has the highest affinity for O2!
Both HbF and Mb have higher affinity for O2 than adult haemoglobin (HbA), so can “steal” O2 from HbA.
What is carbaminohaemoglobin?
When CO2 binds to haemoglobin for transport to the lungs.
How does the chloride (Hamburger) shift relate to transport of CO2?
CO2 isn’t soluble in blood, so moves into RBCs and is converted to HCO3- by carbonic anhydrase. HCO3- leaves RBC in 1:1 ratio with Cl- to maintain neutral charge. This is the chloride shift. CO2 transported as HCO3- to the lungs, where it then re-enters RBCs again in exchange for Cl- as reverse chloride shift, and is converted back into CO2, which is diffused into alveoli and exhaled.
How is CO2 transported in the blood?
As carbaminohaemoglobin (CO2 bound to haemoglobin)
As HCO3- (converted in RBC then moved into blood by chloride shift)
As CO2, directly dissolved in plasma (10%).
How long does it take for bone marrow to produce RBC and what is this process called?
3 weeks. Erythropoiesis.
Where is erythropoietin produced?
In the kidney (peritubular fibroblasts).
How are old RBCs removed and what is this process called?
Surface changes e.g. damage recognised by macrophages and RBC is digested by them in the spleen and liver. Erythrophagocytosis.
