Cardio-Respiraoty Week Two Flashcards
What is the tunica externa (adventitia) composed of?
This is the outer layer with thick loose connective tissue. Collagen and elastin are arranged longitudinally. There is the vasa vasorum present.
What is the tunica media composed of?
There is concentric layers of smooth muslces and layers of elastic fibres. There is type one collagen and proteoglycans.
What is the external elastic lamina?
This is part of the tunica media and separates this layer from the tunica externa.
What is the tunica intima composed of?
This has a single layer of endothelium in contact with the blood. There is then a basement membrane with a collagen framework for strength. The outer layer has the internal elastic lamina which has openings to allow diffusion from tunica media.
What are the two main types of arteries called?
Elastic and Muscular
What are some examples of elastic arteries?
Pulmonary, Aorta, Subclavian and Common iliac
What are the characteristics of elastic arteries?
There is a well defined intima with supporting collagen. The tunica media has a high elastin concentration and it is arranged as lamellae. The elastin will hold mechanical energy and then recoil allow blood to flow. There tunica externa is thinner than the media.
How is elastin arranged in elastic arteries?
Lamellae
What are some examples of muscular arteries?
Cerebra, Popliteal, Brachial
What are the characteristics of muscular arteries?
Their tunica media has a higher proportion of smooth muslce than elastin. Their media is thicker than the lumen which means there are resistant to collapsing. Their externa is thicker than their media. Their external elastic lamina is thin.
What are the characteristics of arterioles?
Their interna is very thin and is fenestrated. Their media has 1-2 layers of circular smooth muslce and the distal end forms a pre-capillary sphincter. Their externa is loose connective collagenous tissue. The terminal end is called a metateriole.
What are the main features of capillaries?
Their intima only has endothelium and basement membrane. There is no externa or media.
They are surrounded by pericytes which are involved in contraction.
What are the three types of capillaries?
Continuous, Fenestrated and Sinusoids.
What are the characteristics of continuous capillaries?
The walls have continuous endothelial layer with narrow clefts between cells.
What are the characteristics of fenestrated capillaries?
These are mainly found in tissues specialised for bulk fluid exchange eg exocrine glands and kidneys. Their endothelial cells have fenestrations for free passage of molecules (water and salt0.
What are the characteristics of Sinusoids (discontinuous)?
These are found in liver, spleen and bone marrow. They are have large gaps big enough for red blood cells and plasma.
What layers do metaterioles have?
Intima: endothelium and BM
No media
Sparse externa
What are the characteristics of venules?
They have a defined tunica interna and 1-2 layers of circular muslce. The externa is sparse.
What are the characteristics of veins?
The tunica externa is the thickest. There is no internal or external lamina. The tunica intima folds to form valves/
What type of muscle do pulmonary veins have?
Cardiac
What are anterio-venous shunt vessels?
They are specialized connections between venules and metaterioles. and they can avoid capillaries.
What are end arteries?
An Artery that is the only supply of oxygenated blood to a portion of tissue.
What is the difference between systolic BP and diastolic BP?
Systolic: highest pressure attained in arteries during systole
Diastolic: lowest arterial pressure during diastole
What is the Blood pressure in capillaries?
35mmHg
How is MAP calculated?
MAP = diastolic BP + 1/3 ( systolic - diastolic) MAP = CO x TPR
How does blood volume affect blood pressure?
An increase in blood volume ( for example from water retention) will increase blood pressure.
A decrease of blood volume above 10% of total volume with no homeostatic mechanisms will decrease blood pressure.
What three factors does vascular resistance include?
- Lumen size
- Blood viscosity
- Blood vessel length
How does lumen size affect blood pressure?
The small the lumen, the greater the resistance and the greater the blood pressure. Vasoconstriction narrows the lumen.
What is vascular resistance?
This is the opposition to blood flow
How does blood viscosity affect blood pressure?
The higher the viscosity, the higher the resistance and the higher the blood pressure.
Conditions increasing blood viscosity include dehydration and polycythaemia.
Conditions that decrease blood viscosity include anaemia or haemorrhage.
How does blood vessel length affect blood pressure?
The longer the vessel, the greater the resistance.
Obese people will have a high BP due to additional blood vessels in adipose tissue.
What is venous return?
This is the volume of blood returning back to the heart. The pressure difference of venules compared to right ventricle is 16mmHg to 0mmHg.
What is the skeletal muscle pump?
This promotes venous return during normal locomotory activity. When moving upright, blood volume will generally flow to peripheral areas. To combat this, muslces involved in standing will contract and help VS to the heart.
How does velocity of blood flow affect blood pressure?
Blood velocity is inversely related to cross-sectional area.
Each time an artery branches, the cross-sectional area increase and hence the blood velocity decrease as it flows away from the heart. The pressure decreases as velocity decreases.
What is blood velocity inversely related to?
Cross-sectional area. The flow is slowest when area is greatest.
Where is the cardiovascular centre located?
Medulla oblongata
What is the role of Baroreceptors?
These are mechanoreceptors located in carotid sinus and aortic arch. They detect wall stretch from pressure changes. The less stretched, the less impulses fired through glossopharyngeal (carotid sinus) and Vagus nerve (aortic arch).
Which baroreceptors are the Vagus and Glossopharyngeal nerve attached to?
Vagus: Aortic arch
Glossopharyngeal: Carotid sinus
What is the role of Proprioceptors?
These monitor the limb position. They provide input during physical activity. Their activity accounts for rapid increase in heart rate during exercise.
What is the role of chemoreceptors?
These are close to the baroreceptors and they monitor concentrations of oxygen, carbon dioxide and pH.
What is the role of ADH in blood pressure regulation?
This is made in hypothalamus and secreted/stored in posterior pituitary.
When Osmo recepotrs in hypothalamus detect low BP, ADH is released. They act on the collecting ducts to promote water retention. This increases blood volume and decreases urine production. This therefore decreases blood pressure
What is the role of Aldosterone in blood pressure regulation?
This is secreted by adrenal cortex when there is low blood pressure. This acts on the DCT and CD to promote sodium retention and potassium secretion. This increases blood volume and blood pressure.
What is the role of Angiotensin II in blood pressure regulation?
This is formed when there is low Blood pressure, low blood volume or blood flow to kidney decreases.
Angiotensin II is a vasoconstrictor and raises BP by increases systemic vascualr resistance. It also stimulates aldosterone releases and the thirst sensor.
What is the role of ANP in blood pressure regulation?
This is released from right atrium when there is excessive stretching during diastole. It promotes sodium/water loss and results in decreased blood volume, hence reducing blood pressure. It blocks the release of ADH, NA and aldosterone and renin.
What is the role of Adrenaline and Noradrenaline in blood pressure regulation?
The adrenal medulla secrets these in response to sympathetic response. They act on alpha-one receptor on blood vessels and causes vasoconstriction. They increase heart rate by acting on beta-one receptors. They increase blood pressure.
What is the role of erythropoietin in blood pressure regulation?
This is secreted by the kidney and increased the oxygen capacity of the blood.
What are the stages of Hypertension?
Stage one: clinic BP is 140/90mmHg or higher and ABPM is 135/85mmHg or higher.
Stage two: clinic BP is 160/100mmHg or higher and ABPM is 150/95mmHg or higher.
Severe: the systolic is 180mmHg or higher or diastolic is 110mmHg or higher.
What is the difference between primary and secondary hypertension?
Primary: this is 90% of cases and is due to risk factors
Secondary: this is 10% of cases and is a result of another condition. This can be pregnancy, endocrine, renal damage, pheochromocytoma
What is pheochromocytoma?
Tumour in adrenal glands causing high amounts of catecholamines, mostly norepinephrine, plus epinephrine to a lesser extent.
What are some of the clinical patterns associated with hypertension?
- increased heart workload causes left ventricular hypertrophy. The increased muscle mass will have a higher oxygen demand and this may lead to MI or ischaemia.
- increased blood pressure will place physical stress on blood vessel walls and this may cause arteriosclerosis, haemorrhages and aneurysms.
- renal or heart failure
- retinopathy (vessels supplying retina often affected)
What are some examples of ACE inhibitors?
These drugs end in ‘pril’.
Captopril, Enalaprill, Ramipril, Lisinopril
What is the mechanism of action of ACE inhibitors?
This inhibits the enzyme responsible for converting angiotensin I to angiotensin II.
This causes:
- decreased peripheral resistance
- decreased aldosterone causing decreased sodium/water retention
- dilation of arteries
- sympathetic activity decrease
What are some side effects of ACE inhibitors?
- There is reduced bradykinin breakdown, peptide which activates sensory nerves in the lung, and hence this causes a dry cough
- Sudden fall of blood pressure on first dose
What at some examples of Angiotensin receptor blockers?
These end in ‘Sartan’
Candesartan, Losartan
What is the mechanism of action of Angiotensin receptor blockers?
These block the Angiotensin receptor (which mediates the vasoconstriction and aldosterone released actions of angiotensin II).
What are some side effects of Angiotensin receptor blockers?
They do not inhibit bradykinin breakdown and hence there is no dry cough.
Side effects include headache, dizziness, back pain and diarrhoea.