Basic Vascular System Flashcards
Are mesodermally derived structures vascularised?
Yes - except for articular cartilage
From which germ layer are vascularised structures derived?
Mesoderm
Except for articular cartilage
What is an embolus?
A moving thrombus
What is an end organ?
An organ supplied by an end artery
What are perforating veins?
Superficial veins penetrating deep fascia to deep veins
What are the three layers of an artery?
Intima
Media
Adventitia
What is the makeup of the intima?
Connective tissue lined with epithelium
What is the makeup of the media?
Concentrically-arranged smooth muscle fibers, elastic fibers
Sympathetic innervation
What is the makeup of the adventitia?
Mostly collagen fibers
Vasomotor nerves, which convey neurons to the media
Two classes of arteries
Elastic
Muscular
Factor determining whether an artery is elastic or muscular
Composition of media
Role of elastic arteries
Prevent blood pressure drop during diastole
Location of elastic arteries
Closest to heart
EG: aorta
Composition of elastic artery media
Mostly elastin fibers
Gives a yellow colour
Another name for elastic arteries
Conducting vessels
Composition of muscular artery media
Mostly smooth muscle
Role of muscular arteries
Distribute blood according to demand by contracting or dilating
Another name for muscular arteries
Distribution vessels
Layout of muscular arteries
Branch extensively, gradually reducing calibre
Another name for arterioles
Resistance vessels
Which type of vessel has the greatest wall thickness:lumen calibre ratio?
Arterioles
Role of arterioles
Contract, dilate to redistribute blood to different capillary beds
Arterial branches in the trunk
Parietal
Visceral
What can the arterial branches be? 1) 2) 3) 4) 5) 6)
1) Blood vessels
2) Articular
3) Muscular
4) Cutaneous
5) Arteriae nervorum
6) Nutrient (to long bone)
BAMCAN
What is an anastomosis?
A linking of tubular structures
The fusion of two arteries without an intervening capillary bed
Common locations of arterial anastomoses
Where blood supply could be cut off, EG in a joint articulation (elbow)
Common in very vascularised structures (lips, hips)
Can functional end arteries anastomose?
Yes, at the arteriolar level
Examples of anatomical end arteries
Retina (central retinal artery)
Fingertips, toetips
Penis
Structure of veins
Intima
Media
Adventita
Differences between veins and arteries 1) 2) 3) 4)
1) Veins have less thick walls, greater luminal calibre
2) Less smooth muscle in venous media
3) Higher blood volume, lower pressure in veins
4) Veins have valves
How much blood volume is in the venous system at any one time?
~70%
What are venous valves?
One-way
Bicuspid endothelial folds
Where are venous valves mostly located?
Deep limb veins, superficial veins
Where are there no venous valves?
Deep trunk veins
Where are valves often located in a vein?
At the beginning, end of a vein
Distal to the entry of a major tributary
Where are veins normally located?
Often follow the path of arteries
In places where venous return can be maximised
How is venous blood returned to the heart?
Muscle pump
Thoracic pump
Venae comitantes
Muscular pump
Muscle contraction compresses veins, pumps blood
Main source of blood flow from limbs
Thoracic pump
1) Inspiration - Diaphragm lowers SVC lengthens, fills with blood IVC shortens, pumps blood into heart Negative intrathoracic pressure (by ~1mmHg)
2) Expiration Diaphragm rises SVC shortens, pumps blood into heart IVC lengthens, fills with blood Positive intrathoracic pressure
Venae comitantes/vascular pump
Pair of intercommunicating veins wraps around an artery
Arterial pump compresses veins during systole, pumps blood
Venous valve incompetence
Cusps of valves fail to close properly
Often damage to bicuspid valves
Effect of venous valve incompetence in lower limbs
Blood in deep veins (of calf) squeezed into superficial veins, instead of towards heart
Ulceration of skin
Varicose veins
Abnormal vein dilation
Can be a cause and effect of venous valve incompetence
Do lymph vessels have valves?
Yes
Direction of lymph flow
Superficial to deep
Ultimately draining to subclavian area
Drained into venous system
Which structures drain lymph back into the venous system?
Lymphatic trunk
Thoracic duct
Right lumphatic duct
Major lymph nodes
Cervical
Axillary
Inguinal
Other areas of lymphatic tissue 1) 2) 3) 4)
1) Thymus
2) Spleen
3) Peyers patches
4) Tonsils
