Anatomy: blood and lymph circulation Flashcards
What is sympathetic tone of arteriolar smooth muscle?
a background, low level of contraction
due to tonic (continuous) conduction of action potentials to arterioles by sympathetic nerves
What are the four parts of the aorta?
The ascending aorta
The arch of the aorta
The thoracic aorta
The abdominal aorta
How many branches does the ascending aorta have?
2- the left and right coronary arteries
How many branches does the arch of the aorta have?
3
How many branches does the thoracic aorta have?
Numerous
how many branches does the abdominal have?
3 unpaired midline branches
3 paired , bilateral branches
What are the three branches of the arch of the aorta?
The brachiocephalic trunk
The left common carotid artery
The left subclavian artery
What does the brachiocephalic trunk bifurcate into?
The right common carotid artery
The right subclavian artery
What does the right common carotid artery bifurcate into?
The right internal carotid artery
The right external carotid artery
What happens to the right external carotid artery?
What does it supply?
remains external to cranial cavity to supply face & scalp
What happens to the right internal carotid artery?
What does it supply?
becomes internal to cranial cavity via the carotid canal to supply the brain
Name an artery that branches off of the right subclavian artery and ascends in the neck .
Where does it go?
The right vertebral artery
Passes through transverse foraminae in cervical vertebrae then through foramen magnum to enter the cranial cavity
Where is the circle of Willis?
What is it?
On the inferior aspect of the brain
It is an anastamosis
What is formed when the left and right vertebral arteries join together?
The basilar artery
It is found on the inferior aspect of the brain
What is the carotid sinus?
Where is it located?
The most proximal (usually dilated) part of the internal carotid artery
It is located at the level of the superior border of the thyroid cartilage
What innervates the carotid sinus?
the glossopharyngeal nerve (CN IX)
What is the function of the carotid sinus?
to detect stretching of the walls of the carotid sinus (i.e. beat to beat changes in arterial blood pressure)
What does the carotid body do?
What innerverates it?
It is also supplied by CN IX
It monitors blood gas levels/pH
Describe the blood brain barrier
there are tight junctions between brain capillary endothelial cells (brain capillaries are not leaky)
There are also astrocyte (support cell) processes surround the brain capillaries
The combined effect is to prevent the diffusion of some substances from capillary into brain tissue e.g. some antibiotics
What substances can diffuse through the blood brain barrier?
O2/CO2 and ethanol
What weakens the blood brain barrier?
brain injury, inflammation and neoplasia
What are anastamoses?
Why are they useful?
the arteries connect with each other without an intervening capillary network
the presence of an anastomosis provides alternative routes for blood to flow to supply the cells distal to an arterial occlusion
Why are anastamoses in the brain useful?
can help to prevent a cerebrovascular accident (CVA)
What is each alternative route in any given anastamosis called?
A collateral
What is a disadvantage of collateral arteries?
collaterals bleed from both sides of a cut so the haemorrhage can be worse
What is an end artery?
the ONLY arterial blood supply to a given area of the body (there are no collaterals)
Describe the path of the left subclavian artery
The left subclavian artery passes under the clavicle then becomes the left axillary artery.
It then becomes the left brachial artery.
The brachial artery bifurcates anterior to the elbow joint to give the left radial artery and the left ulnar artery.
What are the branches from the thoracic aorta’s anterior surface?
bronchial arteries (arterial blood for the lung tissue) oesophageal arteries mediastinal arteries pericardial arteries phrenic arteries
What are the bilateral branches from the thoracic aorta?
bilateral posterior intercostal arteries which supply the chest wall
What does the abdominal aorta bifurcate into?
The right and left common iliac arteries
What do the right and left common iliac arteries supply?
the pelvis/perineum & the lower limbs
What does the left common iliac artery bifurcate into?
What do these new arteries supply?
The left external iliac artery which supplies the lower limbs
The left internal iliac artery which supplies the pelvis and perineum
Where is the carotid pulse found?
at the bifurcation of the common carotid artery
posterior to and at the level of the thyroid cartilage
What name is given to the branches that merge to form a larger vein?
Tributaries
What percentage of the circulating blood volume do veins contain at rest?
60%
What is the purpose of the thin layer of smooth muscle in the walls of veins?
It can contract to reduce venous capacity and return blood to the arterial side of the circulation (e.g. in haemorrhage)
Is the course of a vein usually straight or tortuous?
Straight
Is venous blood flow pulsatile or non-pulsatile?
Non-pulsatile (except in the jugular vein)
How is venous blood pumped back towards the heart?
the contraction of skeletal muscles in the lower limb (“skeletal muscle pump”)
chest cavity pressure changes associated with the movements of breathing
venous pumps require the presence of venous valves in limb veins to ensure unidirectional flow back to the heart against gravity
How many sets of veins are there?
2 superficial veins (smaller and run within superficial fascia then drain into deep veins (larger and run deep to the deep fascia & in cavities often in NVB)
What is the circulatory system?
The cardiovascular system and the lymphatic system
Describe what happens to tissue fluid that becomes lymph
lymphatic capillaries collect tissue fluid (the fluid that normally leaks out when blood flows through capillary beds)
once in the lymphatic capillaries the fluid is called lymph
lymphatic capillaries from tissues/organs join together the form lymphatics (lymphatic vessels)
lymphatics carry lymph through lymph nodes (contain white blood cells to filter out foreign particles and fight infection/cancer)
eventually lymph is returned into the central veins in the root of the neck
Which main ducts does lymph drain into?
The right lymphatic duct or the thoracic duct
Where does lymph in the right lymph duct drain into?
The right venous angle (where the central veins returning from the head/neck and upper limbs meet)
Where does lymph in the thoracic duct drain into?
The left venous angle (where the central veins returning from the head/neck and upper limbs meet)
