Circulatory System Flashcards
Blood flows in two main circuits
- Systemic circulation
* Pulmonary circulation
Blood vessels
artery
vein
capillaries
carries blood away from the heart
artery
carries blood toward the heart
vein
can take higher pressure
artery
Artery and Vein 3 layers (from lumen side)
Tunica interna
Tunica media
Tunica externa
- Endothelium
- Basement membrane
- Internal elastic lamina
Tunica interna
Has smooth muscle and elastic fibers
Tunica media
• Has elastic and collagen fibers
• Contains nerves and the vasa vasorum
• Anchors vessel to surrounding
tissue
Tunica externa
Artery
Elastic artery
Muscular artery
Arteriole
• Large caliber (e.g. aorta and its branches, pulmonary artery)
• Thin walls (1/10th of diameter)
• Thick tunica media with more abundant elastic fibers than smooth
muscles
• Expands during ventricular systole
• Elastic recoil of walls constricting lumen propel blood forward during
ventricular diastole
• Conducting artery
Elastic artery
• Medium-sized artery (e.g. brachial artery, radial artery, femoral artery,
specific organ arteries)
• Thick walls (3/4th of diameter )
• More abundant smooth muscles than elastic fibers (up to 40 layers of
smooth muscles), always in a partial state of contraction (vascular
tone)
• Readily vasoconstricts and vasodilates to regulate blood flow, low
recoil capability
• Distributing artery
Muscular artery
• Microscopic vessels which regulate blood flow into
capillary network
• Wall is 1⁄2 vessel diameter
• Tunica media has 1 -2 smooth muscle cell layers with
a precapillary sphincter at the metarteriole (most
distal region)-capillary junction
• Its small diameter and constriction of walls by smooth
muscle contraction increase resistance to blood flow
and decrease blood into capillaries
• Resistance artery
Arteriole
where artery and vein would meet.
Where oxigen, carbon dioxide, nutrition exchange location.
capillaries
Smallest of the blood vessels, measuring 5 - 10μm in diameter, connect arterioles and venules No tunica media and tunica externa Has a single
-cell wall, the endothelium,
enables the interchange of water, oxygen,
carbon dioxide, other nutrient and waste
chemical substances driven by hydrostatic and
colloid osmotic pressures inside the capillary
and surrounding tissues (cells and interstitial
space)
Exchange vessels
RBC (diam=8μm) need to fold a little to pass
single file thru the capillaries
capillaries
• Found near all the cells of the body
• Distribution dependent on the tissue’s metabolic
activity
• Higher metabolic activity (e.g. brain, muscles, liver,
kidneys, CNS), more oxygen and nutrient
requirements, the denser the capillary network vs.
lower metabolic activity tissues (e.g. tendons,
ligaments)
• Absent in epithelium, cartilage, lens and cornea
capillaries
damaged veins that leads to backflow
varicose veins/varices
backflows are prevented by
valves
varicose veins reason
incompetent venous valves
there is blood backflow
Can also be found in the
esophagus and anal canal
varicose veins/varices
Main exit from left ventricle
AORTA
AORTA
One continuous vessel
named into four parts
- Ascending
- Arch (T4-T5 disc)
- Thoracic (left of vert bodies)
- Abdominal (Up to L4)
supplies 80% of the brain
Internal Carotid a
supplies the
structures internal to the skull
Internal carotid a
supplies the
structures external to the skull
External carotid a
Common Carotid
Internal carotid
External carotid
allows for proper blood flow from the arteries to both the front and back hemispheres of the brain.
Circle of Willis
• Communicating arteries connecting the left and right anterior
circulation
• Anterior circulation (fr internal carotid aa) connected to posterior
circulation (fr vertebral aa) via the basilar a
REDUNDANT BLOOD SUPPLY
• Begins at the superior border of the larynx until the temporomandibular joint where it divides in the parotid gland and branches as the • Superficial temporal a • Maxilla a
External carotid (external to the neck)
Carotid sinus has
baro receptor
right direct to the heart
Subclavian artery
shoulder artery
Subclavian artery
Gives off the vertibral Artery and axillary Artery
Subclavian artery
major br to the brain, passes thru the transverse foramina of cervical vertebrae C6 to C1 into the foramen magnum
Vertibral Artery
• Joins the vertebral a of the other side to form the basilar a
Cerebral Circle of Willis
give 20% blood supply to the brain
basilar artery
proximal stenosis of subclavian artery, resulting
in retrograde flow from circle of willis to vertebral artery to supply the arm,
symptoms result from
hypoxia of the brain
Subclavian steal syndrome
increase chance of coma or brain damage
hypoxia of the brain
Continuation of the subclavian artery into the upper limb deep to the clavicle after the lateral border of the 1st rib, divided by the pectoralis minor m into 3:
Axillary artery
• Continuation of the axillary artery into the arm
• Superficial, passes medial to the humerus then
anteriorly into the cubital fossa
• Brachial a pulses can be palpated and ausculatated here
when taking the blood pressure of a person.
Brachial artery
• Radial and ulnar aa
anastomose in the hand
via superficial and deep
palmar arches.
Palmar arches
below thumb artery
Radial
below pinky artery
ulnar
supplies blood to stomach
Celiac trunk (T12 level)
• 5 branches-Inferior pancreaticoduodenal, Jejunal and Ileal,
Ileocolic, Right colic, Middle colic
• Supplies the gut as described in their names
upper abdominal
Superior mesenteric (L1)
3 branches
• Left colic- transverse and descending colon
• Sigmoid- descending and sigmoid colon
• Superior rectal- rectum
lower abdominal
Inferior mesenteric (L3)
(sphenoid bone) drain the
ophthalmic and cerebral
vv
cavernus sinus
very dangerous. can cause death
cavernus sinus thrombosis
biggest vein
inferior vena cava
supplies liver
hepatic portal vein
Results from a severe and
chronic block of the portal
route (e.g. thrombosis of the
portal vein or liver cirrhosis)
portal hypertension
portal hypertension:
If dilated, the alternate
systemic route may manifest
with:
- esophageal varices
- hemorrhoids
- caput medusae
