Blood Vessels Peripheral Circulation Flashcards
Types of Blood Vessels
Arteries—carry blood away from the heart • Capillaries—smallest blood vessels – The site of exchange of molecules between blood and tissue fluid • Veins—carry blood toward the heart
Types of blood vessels
Elastic arteries (diameter 1 - 2.5 cm)
conduct blood
• Muscular arteries (diameter 0.3 mm – 1.0cm)
distribute blood
• Arterioles (diameter 10 µm to 0.3 mm)
• Capillaries (diameter from 8–10 µm)
• Venules (diameter from 8–100 µm)
• Veins
Three layers (tunics) of arteries
Lumen: central blood-filled space of a vessel
• Tunica intima:
– Endothelium composed of simple
squamous epithelium
– Subendothelial layer
– Internal elastic membrane
• Tunica media: sheets of smooth muscle and
elastic fibers, and external elastic membrane
• Contraction—vasoconstriction
• Relaxation—vasodilation
• Tunica externa—composed of collagen fibers
Elastic Arteries for conducting blood
• The largest arteries
• Diameters range from 2.5 cm to 1 cm
• Includes the aorta and its major branches
• Sometimes called conducting arteries
• High elastin content dampens surge of blood pressure
• Vasa vasorum: network of small blood vessels which supply
large vessels
Muscular arteries for distributing blood
Lie distal to elastic arteries • Diameters range from 1 cm to 0.3 mm • Includes most named arteries • Tunica media is thick • Unique feature: internal and external elastic membranes that dampen the pulsatile pressure produced by the heartbeat
Arterioles
Smallest arteries • Diameters range from 0.3 mm to 10 µm • Larger arterioles possess all three tunics • Diameter of arterioles controlled by: • Local factors in the tissues • Autonomic nervous system
Capillaries
Smallest blood vessels with diameter 8–10 µm
• Red blood cells pass through in single file
• Site-specific functions of capillaries include:
• Lungs: oxygen enters blood, carbon
dioxide leaves blood
• Small intestines: receive digested
nutrients
• Endocrine glands: pick up hormones
• Kidneys: remove of nitrogenous wastes
Poorly vacularized tissues
• Tendons and ligaments—poorly vascularized • Epithelia and cartilage—avascular – Receive nutrients from nearby connective tissue
Capillary beds
• Networks of capillaries running through
tissues
Precapillary sphincters
• Regulate the flow of blood to tissues
• When relaxed, the precapillary sphincters are
open and the blood runs through the true
capillaries
• When constricted, the precapillary sphincters
are closed and the blood runs through the
metarteriole thoroughfare channel and
bypasses true capillaries
Types of capillaries
• Continuous capillaries: lowest permeability;
form the blood brain barrier
• Fenestrated capillary: large fenestrations
(pores) increase permeability in small
intestines and kidneys
• Sinusoidal capillary: most permeable with
wide open intercellular clefts in bone marrow,
liver and spleen
Continuous capillaries
Most common type
• Relatively low permeability
• Found in skin, muscle, blood brain barrier
• Capillaries have complete tight junctions of endothelial
cells which prevent functional intercellular clefts
• Vital molecules pass through via highly selective
transport mechanisms
• Not a barrier against oxygen, carbon dioxide, and some
drugs (e.g. anesthetics) so these pass through the
blood brain barrier
• The lowest permeability continuous capillary is in the
CNS and forms the blood brain barrier
Pericytes
around continuous capillary
• Contractile cells that wrap around endothelial cells • Embedded in basement membrane of endothelial cells and communicate with and help sustain endothelial cells
Fenestrated capillaries
Large fenestrations (pores) result in increased permeability • Found in kidneys & small intestine
Summary of Routes of
Permeability into and out of
capillaries
• Direct diffusion through endothelial cell
membranes
• Through pinocytotic vesicles
• Through fenestrations
• Through intercellular clefts (especially
in sinusoidal capillaries)
Sinusoidal capillaries
- Most permeable capillaries
- Wide open intercellular clefts (gaps of unjoined membrane through which small molecules can enter and exit)
- Usually fenestrated
- Incomplete basement membrane
- Have a large diameter and twisted course
- Occur in bone marrow, liver, and spleen
Venules and veins
• Conduct blood from capillaries toward the
heart
• Blood pressure is much lower than in arteries
• Smallest veins—called venules
– Diameters from 8–100 µm in venules
– Smallest venules—called postcapillary
venules
• Venules join to form veins
• Tunica externa rich in collagenous tissue is
the thickest tunic in veins
Mechanisms to help move venous blood
• Valves in some veins particularly in limbs • Skeletal muscle press against vein walls and help pump blood toward the heart
Vascular Anastomoses
Vessels interconnect to form vascular anastomoses – Organs receive blood from more than one arterial source • Neighboring arteries form arterial anastomoses – Provide collateral channels • Veins anastomose more frequently than arteries
Vasa Vasorum
-Vessels of vessels
-network of small blood vessels
which supply large vessels
• Tiny arteries, capillaries, and veins
nourish outer region (tunica externa) of
large vessels
• Inner half of large vessels receive
nutrients from luminal blood
Pulmonary Circulation
- Pulmonary trunk leaves the right ventricle, divides into right and left pulmonary arteries and carries de-oxygenated blood to lungs
- Superior and inferior pulmonary veins carry oxygenate blood into the left atrium
Systemic arteries
Carry oxygenated blood away from the
heart
• Aorta—largest artery in the body
The Aorta 1
Ascending aorta—arises from the left ventricle – Early branches form coronary arteries • Aortic arch—lies posterior to the manubrium and has these branches: • Brachiocephalic trunk: right common carotid and right subclavian branch off this • Left common carotid • Left subclavian artery
The Aorta 2
Descending aorta—continues from the
aortic arch
– Thoracic aorta—in the region of T5–T12
– Abdominal aorta—ends at L4
• Divides into right and left common iliac
arteries
Common Carotid Arteries
Located in the anterior triangle of the neck • Two branches of the common carotid artery – External carotid artery – Internal carotid artery
External carotid artery branches
- Superior thyroid artery
- Lingual artery
- Facial artery
- Occipital artery
- Superficial temporal artery
- Posterior auricular
- Maxillary artery
Internal carotid artery branches
Ophthalmic artery
• Anterior cerebral artery
• Middle cerebral artery
Cerebral artery circle
• The cerebral artery circle forms a loop around
the pituitary gland and optic chiasm and
unites the brain’s anterior and posterior blood
supplies which are provided respectively by
the internal carotid (anterior blood supply)
and vertebral arteries (posterior blood
supply)
Cerebral artery circle
• Vertebral arteries extend off subclavian artery and
supply blood to posterior brain
• Vertebral arteries merge to form the unpaired
basilar artery which ascends along ventral midline of
brain stem and at border of the pons and midbrain it
divides into a pair of posterior cerebral arteries
• Posterior communicating arteries connect the
posterior cerebral arteries to the middle cerebral
arteries anteriorly
• The anterior cerebral arteries extend off the middle
cerebral arteries and are connected by the anterior
communicating artery
Arteries of the arm
Subclavian artery enters the axilla as the axillary artery • Axillary artery becomes the brachial artery at the inferior border of teres major muscle
Arteries of forearm and hand
Brachial artery divides into radial artery
and ulnar artery which transition into
superficial and deep palmar arches
and digital arteries
Arteries of the Abdominal Aorta
Inferior phrenic • Celiac trunk • Superior mesenteric • Suprarenal (adrenal) • Renal • Gonadal (testicular or ovarian) • Inferior mesenteric • Common iliac
The Celiac Trunk its main arterial
branches supply viscera in the superior
part of the abdomen
• Three main branches of the celiac
trunk are the left gastric, splenic, and
common hepatic arteries.
• The celiac trunk and its branches send
arteries to the stomach, liver,
gallbladder, pancreas, spleen, and
duodenum
Superior & Inferior Mesenteric Arteries
• From the superior mesenteric artery,
arteries extend to the jejunum, ileum, and
the proximal half of the colon (cecum,
appendix, ascending colon, and part of the
transverse colon)
• From the inferior mesenteric artery,
arteries extend to the distal half of the
colon (2nd half of the transverse colon,
descending colon, sigmoid colon, and
rectum)
Artery branches off the internal iliac
- Gluteal
- Obturator
- Internal pudental
- Vesical
- Uterine
Arteries of the Pelvis and Lower Limbs
Internal iliac • External iliac • Femoral • Popliteal • Anterior tibial • Posterior tibial • Fibular • Dorsalis pedis • Plantar • Plantar arch
Systemic Veins
• Three major veins enter the right atrium • Superficial veins lie just beneath the skin • Veins have valves which prevent the backflow of blood • Multivein bundles—venous plexuses • Unusual patterns of venous drainage – Dural sinuses – Hepatic portal system
Venous supply into right atrium
Superior vena cava: returns blood from body regions superior to the diaphragm • Inferior vena cava: returns blood from body regions inferior to the diaphragm • Coronary sinus: returns blood from cardiac muscle
Coronary sinus
supply into Right Atrium
Right atrium receives blood via the
coronary sinus (large vein) in posterior
part of coronary sulcus which receives blood
from cardiac veins (great, middle, and small
cardiac veins)
Dural sinuses in brain
• Venous channels found between dura
mater and the brain
• Walls of the dural venous sinuses are
lined with endothelium
• Internal jugular vein drains the dural
venous sinuses
Dural sinuses of Head & Neck
Dural sinuses – Superior and inferior sagittal sinuses – Straight sinus – Transverse sinuses – Sigmoid sinus – Cavernous sinus
Veins of the Head and Neck
• Venous drainage of head & neck into bracheocephalic vein: – Internal jugular – External jugular – Vertebral
Deep Veins of the upper limbs which
follow path of companion arteries
subclavian • axillary • brachial • radial • ulnar vein • deep palmar arch • digital
Superficial veins of the upper
limbs easily visible beneath skin
Cephalic • Basilic • Median cubital (common site to draw blood) • Median antebrachial of the forearm
Superficial Veins of Right Upper Limb
• Form anastomese frequently
• Median cubital vein is used to obtain
blood or administer IV fluids
Veins of the Thorax
- Azygos
- Hemiazygos
- Accessory hemiazygos
- Intercostal
Veins of the Abdomen
Inferior phrenic • Hepatic • Suprarenal • Renal • Lumbar • Gonadal (testicular or ovarian)
Hepatic Portal System
A specialized part of the vascular circuit
• Picks up digested nutrients from the
stomach and intestine and delivers
nutrients to the liver for processing and
storage
Hepatic portal system
• Series of vessels in which two separate capillary
beds lie in between arterial supply and final venous
drainage
• Capillary beds in the stomach and intestines
receive digested nutrients and then drain into the
hepatic portal vein
• Hepatic portal vein delivers nutrient-rich but
oxygen poor blood to a second capillary bed (the
liver sinusoids) through which nutrients reach liver
cells for processing
• After passing through liver sinusoids, blood enters
hepatic veins and then inferior vena cava thereby
re-entering the general systemic circulation
Superficial Veins of the Pelvis and
Lower Limbs
• Small saphenous vein empties into
popliteal vein which empties into femoral
vein which empties into iliac vein
• Great saphenous vein empties into the
femoral vein which empties into iliac vein
Deep Veins of Pelvis & Lower Limbs
- Iliac
- Popliteal
- Anterior tibial
- Fibular
- Dorsalis pedis
- Plantar
- Plantar arch
- Digital
Disorders of the Blood
Vessels
• Aneurysm: dilation of blood vessel wall
which may burst
• Deep vein thrombosis (clot) of the lower
limb
• Venous disease e.g., varicose veins
• Microangiopathy of small blood vessels
e.g., with diabetes
• Arteriovenous malformation
Atherosclerosis
• Atherosclerosis with fat deposits inside
arteries can begin in young people with
consequences becoming evident in middle
to old age
• Males have more atherosclerosis than
females between ages 45–65
• Females tend to experience heart disease
and atherosclerosis later in life than males
• Atherosclerosis in coronary arteries can lead
to ischemic heart disease
