1. Vessels and Circulation

2. Some embryology first There are at first six pairs of aortic arches
In fish these are connected to the gills
They undergo a transformation in mammals
Birds use the right arch of the fourth pair
Mammals use the left arch of the fourth pair

3. Ventral (anterior) view
Transformation :
4th through 7th
weeks: some persist,
some atrophy
Full set of arches develops,
but not all present at
the same time; (before
transformation)

4. Right side: brachiocephalic trunk
4th arches become:
Left side: aortic arch
Right side: brachiocephalic trunk
Right common carotid a
Right subclavian a
Brachiocephalic trunk

5. What the aortic arches become…
Right common carotid a
Right subclavian a
Brachiocephalic trunk

6. 3 Major types of blood vessels
Body RA RV
Lungs LA LV
Boby
Arteries
Capillaries
Veins
Arteries carry blood away from the heart
-”branch,” “diverge” or “fork”
Veins carry blood toward the heart
-”join”, “merge,” “converge”

7. General characteristics of vessels
Three layers (except for the smallest)
Tunica intima - AKA intima
Tunica media – smooth muscle
Tunica externa - AKA adventitia
Lumen is the central blood filled space

8. Intima is endothelium (simple squamous epithelium)
May have subendothelial layer if 1mm or larger
Tunica media: layers of circular smooth muscles
Lamina (layers) of elastin and collagen internal and external
Thicker in arteries than veins (maintain blood pressure)
Smooth muscle contraction: vasoconstriction
Smooth muscle relaxation: vasodilation
Sympathetic vasomotor nerves of autonomic nervous system regulate

9. Adventitia (t. externa) – longitudinally running collagen and elastin for strength and recoil

10. “muscular” middle sized artery

11. Arteries Carry blood away from the heart
From big to small, these are the categories:
1. Elastic
2. Muscular
3. Arterioles (then these to capillaries)
Pressure diminishes along the route
Elastic arteries: act as conduits
2.5-1 cm diameter
Expand with surge
of blood from heart
Recoil and continue
the propagation of blood
Elastin is thick in media:
dampens the surge of blood
pressure
Aorta and its branches

12. Arteries continued 2. Muscular arteries: act as distributing arteries
Middle sized .3mm-1cm
Changes diameter to differentially regulate flow to organs as needed
Internal as well as external elastic lamina
Most of what we see as “arteries”
Tunica media larger in proportion to the lumen, thus “muscular”

13. Arteries continued 3. Arterioles Smallest: .3mm-10um
Only larger ones have all 3 layers
Regulated 2 ways:
Locally in the tissues
Sympathetic control
Systemic blood pressure (the “BP” we measure) can be regulated through them
Send blood into capillaries
Tunica media has only a few layers of smooth muscle cells

14. Capillaries Heart to arteries to capillaries to veins to heart
Capillaries are smallest
8-10um
Just big enough for single file erythrocytes
Composed of: single layer of endothelial cells surrounded by basement membrane
Universal function
Oxygen and nutrient delivery to tissues
CO2 and nitrogenous waste (protein break-down product) removal
Some also have tissue specific functions

15. Capillaries
There’s a capillary “bed” in almost all tissues

17. Capillary permeability
Direct diffusion through endothelial cell membranes
Only O2 and CO2
Other molecules by various other methods
Blood brain barrier: complete tight junctions
Selective transport of necessary molecules
Lipid soluble agents (like anesthetics) get through, as do O2 and CO2

18. Veins Pressure has been lowered so capillaries can tolerate
With lower pressure, walls (of veins) can be thinner
From smallest to large:
Capillaries to postcapillary venules to venules to veins
Veins are larger than arteries, plus
Tunica externa is thicker
There is less elastin

19. Special features of veins
Valves
Prevent backflow
Most abundant in legs (where blood has to travel against gravity)
Muscular contraction
Aids the return of blood to heart in conjunction with valves
Mechanical issues…
(really good to know)

20. Exercise helps circulation (because muscles contract and squeeze blood back to the heart)

21. Vascular anastomoses Vessels communicating with each other
Veins have more than arteries
Form alternative pathways or collateral channels
Protect organs from being supplied by just one route
Poor anastomoses & therefore vulnerable: central artery of retina, kidneys, spleen, bone diaphyses
Vasa vasorum
Means vessels of the vessels
Blood supply to vessel itself
Smallest vessels don’t need

22. Vascular System (Blood vessels of the body)
Two circulations
Systemic
Pulmonary
Arteries and veins usually run together
Often nerves run with them
Sometimes the systems do not have bilateral symmetry
In head and limbs, most are bilaterally symmetrical

23. Pulmonary Circulation
Pulmonary trunk branches
Right and left pulmonary arteries
Division into lobar arteries
3 on right
2 on left
Smaller and smaller arterioles, into capillaries surrounding alveoli
Gas exchange
Pulmonary system pressure is only 1/6 of systemic blood pressure

24. Pulmonary Circulation
After gas exchange blood enters venules
Larger and larger into Superior and Inferior Pulmonary veins
Four Pulmonary Veins empty into left atrium

26. In lungs

27. Systemic Circulation Oxygenated blood to body
Leaves LV through Ascending Aorta
Only branches are the 2 coronary arteries to the heart
Aortic Arch has three arteries branching from it:
Brachiocephalic trunk, has 2 branches:
Right common carotid a.
Right subclavian a.
Left common carotid a.
Left subclavian a.
Ligamentum arteriosum
connecting to pulmonary a.
remember aortic arches…

28. Descending aorta Thoracic aorta Abdominal aorta
at T12 becomes abdominal aorta
Abdominal aorta
ends at L4 branching into:
R & L common iliac arteries

29. Common carotids branch:
Internal carotids
External carotids
Subclavian: 3 branches
Vertebral arteries
Thyrocerical trunk
Costocervical trunk

30. Head and neck Common carotids just lateral to trachea: feel
At larynx divides into internal & external
External carotid: supplies head external to brain and orbit
Feel superficial temporal a.
Middle meningeal: vulnerable (branch of maxillary)
Internal carotid
Supply orbits and most of cerebrum

31. Internal carotid a. Enters skull through carotid canal Gives off:
Ophthalmic artery
Then divides into anterior and middle cerebral arteries (see next slides):
together they supply 80% of cerebrum

34. Angiogram

35. Middle cerebral arteries run through lateral fissures
arteriogram
Middle cerebral arteries run through lateral fissures
Anterior cerebral arteries of each side, through anterior communicating artery, anastomose
(an anastomosis is a union)

36. * * * * R and L vertebral arteries* (from subclavians)
Ascend through vertebral foramina of C6-C1 transverse processes
Through foramen magnum into skull
Join to form one Basilar artery* * * * *

37. Basilar artery: branches
Divides into posterior cerebral arteries
Posterior communicating arteries connect to middle cerebral arteries
CIRCLE OF WILLIS
Note how it loops around pituitary gland & optic chiasm
(now called “cerebral arterial circle”)

39. Upper limb Subclavian runs laterally onto 1st rib, under clavicle
Enters axilla as axillary artery
Sends branches
Continues as brachial artery in upper arm
Splits into radial & ulnar arteries
See hand supply
Feel brachial & radial pulses

41. overview

42. Thorax
Anterior intercostals branch off Internal thoracic* (branch of subclavian)
Posterior intercostals branch off Thoracic aorta
Intercostal arteries, veins and nerves run just UNDER the ribs *
Small bronchial arteries supply the lung structures

43. Arteries to the abdomen
Arise from the abdominal aorta
At rest, ½ arterial blood is here!
Three single midline branches supply the digestive tube
Celiac trunk
Superior mesenteric artery
Inferior mesenteric artery 1. 2. 3.

44. Superior mesenteric supplies most of intestines
Celiac trunk: divides into 3 right away: left gastric, splenic & common hepatic (see pic; the latter is the only which goes off to the right)
Superior mesenteric supplies most of intestines
Definition of mesenteries: double layered sheets of peritoneum
that support most organs in the abdominopelvic cavity 1. 2.

45. 3. Inferior mesenteric supplies distal half of large intestine
(The 1, 2 and 3 are branches of the abdominal aorta) 1. 2. 3.
Know what these terms mean: phrenic, gastric, hepatic, renal, colic

46. Arteries to the abdomen
Paired branches off the abdominal aorta supply adrenal glands, kidneys, gonads and abdominal body wall
supply diaphragm
supply adrenals
to kidney 3.

48. Abdominal aorta branches into Common iliacs at L4; these branch into
Internal iliacs to pelvic organs, perineum, buttocks, medial thighs
External iliacs: to rest of lower limbs

49. External iliac passes under inguinal ligament becoming Femoral artery
At back of knee femoral becomes popliteal artery, and branches
Feel dorslis pedis & posterior tibial

51. review

52. review

53. Systemic Veins 3 major vessels enter Right Atrium:
SVC (superior vena cava)
IVC (inferior vena cava)
Coronary sinus
Many veins are very superficial (unlike arteries)
Venous plexuses (networks of anastomoses and parallel veins) are very common
Head and hepatic portal systems are unusual

54. Dural sinuses Drain the veins of the brain Cavernous sinuses
Carotid arteries and some cranial nerves run within them
Dangerous if trauma
Come together as sigmoid sinus – becomes Internal Jugular vein
Exits skull through jugular foramen

55. Internal jugular veins
Drain most of blood from brain
Run lateral to internal then common carotid
At base of neck joins subclavian v. to form brachiocephalic v.
External jugulars – drain some of scalp & face

56. Vein overview Azygos system drains the thorax:
Note that unlike the arteries, the veins have a brachiocephalic on the right and left sides
Azygos system drains the thorax:

57. Deep veins of upper limbs follow arteries, most of them double to one artery
Superficial veins: see pic
Blood drawn from median cubital vein in antecubital fossa
(look at)

58. Tributaries of IVC: note asymmetry
Left gonadal and suprarenal veins drain into left renal vein
On right they drain directly into IVC
Right and left hepatic veins enter superior part of IVC

59. Hepatic portal system
Picks up digested nutrients from stomach & intestines and delivers them to liver for processing and storage
Storage of nutrients
Detoxification of toxins, drugs, etc.
Two capillary beds
Route: artery to capillaries of gut to hepatic portal vein to liver’s capillaries to hepatic vein to IVC
Don’t confuse hepatic vein with hepatic portal vein

60. Kind of confusing…
Superior mesenteric and splenic veins join to form hepatic portal vein, which goes up into liver
Inferior mesenteric empties into the splenic vein * *

61. (same info with different pic)
Tributaries of hepatic portal vein:
-superior mesenteric vein
-splenic vein
-inferior mesenteric vein
Hepatic portal system
Picks up digested nutrients from stomach & intestines and delivers them to liver for processing and storage
Storage of nutrients
Detoxification of toxins, drugs, etc.
Two capillary beds
Route: artery to capillaries of gut to hepatic portal vein to liver’s capillaries to hepatic vein to IVC

63. Leg veins Names similar to arteries
Femoral becomes external iliac after crossing under inguinal ligament
External iliac joins with internal iliac to form common iliac vein
_________used for grafting in coronary
artery bypass grafts: is the longest vein in the body

64. Fetal Circulation
The one umbilical vein brings blood which has been to the placenta for oxygenation (by gas diffusion from mom’s blood)
The pair of umbilical arteries (branches from baby’s internal iliac arteries) carry blood to placenta to pick up oxygen and nutrients
Fetal heart starts beating at 21 days post conception

67. Some Diseases Atherosclerotic cardiovascular disease Affecting veins
Cerebrovascular disease – affects brain, strokes
Coronary artery disease (CAD) – arteries of heart
Peripheral vascular disease (PVD) – arterial
Affecting veins
Chronic venous insufficiency – venous = veins
Deep venous thrombosis (DVT)
Aneurysms
Portal hypertension
Hypertension