BIO211 Weekly Guide #3
VASCULAR
SYSTEM
After completing this laboratory you should be able to:
1) Identify the major systemic arteries and state the regions supplied by each
2) Identify the major systemic veins and state the regions drained by each
3) Identify the vessels of the hepatic portal system and describe the functional relationship between each of the organs drained and the liver
4) Identify the pulmonary arteries and veins
5) Identify and distinguish systemic arteries, arterioles, veins, venules, and capillaries in histological section
6) Describe how heart rate and blood pressure are regulated and the anatomical structures involved
7) Conduct simple measures of pulse rate and blood pressure
Guide to Gross Anatomy Guide to Histology Guide to Physiology
Outline
I. Peripheral Circulation
A. Characteristics {FAP 21-Introduction, Fig 21.7}
closed double loop system
heart-->arteries-->arterioles-->capillaries-->venules-->veins-->heart
systemic vs. pulmonary systems - relative blood pressures and resistances
portal systems
B. Blood vessel structure - 3 layered walls {FAP 21-1}
tunica intima
tunica media
tunica externa (adventitia)
C. Arteries {FAP 21-1}
function - high pressure system
vessel structure
elastic vs. muscular arteries
D. Arterioles {FAP 21-1}
function - control of regional blood flow and peripheral resistance
vessel structure
E. Veins and venules {FAP 21-1}
function - reservoir (control of functional blood volume)
structure
valves & venous return "pumps"
F. Capillaries {FAP 21-1}
types and locations
continuous
fenestrated
sinusoidal capillaries, sinusoids, venous sinuses
function - exchange of metabolites, gases, and nutrients
fluid exchange with tissues - hydrostatic vs. oncotic pressures
diapedesis of blood cells
control of local blood flow (capillary sphincters)
specialized barriers
blood-brain barrier
placental barrier
G. Vascular flowchart {FAP 21-6, 21-7; Figs 21.17 to 21.31}
G. Fetal Circulation {FAP 21.8; Fig 21.32}
basic rationale
ducts and shunts
changes at birth
II. Circulatory Physiology (AP 21-2)
A. Vascular resistance, pressure and flow relationships{FAP Fig 21.8}
B. Laminar and nonlaminar flow {FAP Fig 21.7}
C. Vascular volumes
D. Capillary exchange {FAP Fig 21.10, 21.11}
III. Control of Peripheral Circulation {FAP 21-3, 21-4}
A. Neural Control
B. Endocrine Control
IV. Circulatory Assessment
A. Pulse Rate
B. Blood Pressure
C. Angiogram
Gross Anatomy List
Arteries: Veins:
pulmonaries pulmonaries
ascending aorta superior vena cava
coronaries azygos
aortic arch hemiazygos
brachiocephalic brachiocephalics
common carotids internal jugulars
internal carotids subclavians
external carotids external jugulars
subclavians axillaries
vertebrals brachials
axillaries basilics
brachials cephalics
radials coronary sinus
ulnars inferior vena cava
descending thoracic aorta hepatic
bronchials renals
descending abdominal aorta ovarians (or spermatics)
celiac trunk common iliacs
left gastric internal iliacs
splenic (lienal) external iliacs
common hepatic femorals
proper hepatic gt. & ls. saphenouses
gastroduodenal
right gastric
superior mesenteric Hepatic Portal System (Veins):
renals hepatic portal vein
ovarians or spermatics (testiculars) superior mesenteric vein
inferior mesenteric inferior mesenteric vein
common iliacs splenic (lienal) vein
internal iliacs
external iliacs
femorals Fetal Vessels --> Ligaments:
popliteals umbilical arteries -->umbilical ligaments
ant. & post. tibials umbilical vein --> round ligament of liver
peroneals ductus arteriosus --> lig. arteriosum
Key: Know location and function of all structures
Not required
Guide to Gross Anatomy
Systemic Arteries {FAP Fig 21-18 to 21-25; APL Exercises 18-1, 18-3}
For each vessel of the arterial system you should know the location, the major branches, and what regions of the body are supplied. Systemic arteries have thick muscular walls. In cadavers they hold a round cross-sectional shape. In the extremities arteries usually run fairly deeply, suspended by the deep fascia.
a) The first 5 cm of the aorta, as it leaves the heart and travels rostrally is the ascending aorta.
- What are the only two branches of the ascending aorta?
b) The aortic arch runs mediolaterally to the left and somewhat ventrodorsally between the ascending and descending thoracic aorta.
- What three major arteries branch from the aortic arch?
c) On the models and charts identify the following arteries of the upper body and state the regions which they supply (plural names signify arteries which occur bilaterally):
brachiocephalic external carotids axillaries
common carotids subclavians brachials
internal carotids vertebrals
- What is the structural (hisotological) distinction between elastic and muscular arteries? What is the functional significance of this distinction? Where are the elastic arteries located? What is the unique role that compliance (stretchiness) of the elastic arteries performs in regulating blood pressure?
- On which side is the brachiocephalic artery and what are its two major branches?
- Each common carotid branches into an external and an internal carotid at the level of the superior margin of the thyroid cartilage (of the larynx).
- The vertebral artery branches from the subclavian artery. What route does the vertebral artery take through the neck to the skull?
- The axillary and brachial arteries are the direct continuations of the subclavian artery through the axilla (armpit) and arm, respectively. What structures define the limits of the subclavian, axillary, and brachial arteries?
- The two principal branches of the brachial artery are the ulnar and radial arteries which supply the medial and lateral aspects, respectively, of the forearm and hand.
d) The descending aorta has a thoracic portion above the diaphragm and an abdominal portion below. The descending thoracic aorta sends out several parietal branches to the chest wall. The major visceral branches are the bronchials, which supply the metabolic needs of the lungs, and the esophageals.
- Locate the descending thoracic aorta and the aortic hiatus in the diaphragm.
e) As the abdominal aorta descends, it sends out parietal branches to the abdominal walls and visceral branches to the abdominal organs. We will be concerned only with the major visceral branches. On the models and charts identify the following visceral abdominal arteries and state the regions which they supply:
abdominal aorta common hepatic superior mesenteric
celiac proper hepatic renals
left gastric right gastric ovarians or testiculars
splenic gastroduodenal inferior mesenteric
- Study the celiac trunk on the charts and models. What are the three major branches of the celiac artery? What are the three major branches of the common hepatic artery? Note that the right and left gastric arteries anastomose along the lesser curvature of the stomach.
- Note that the superior mesenteric artery usually emerges from the aorta 1-2 cm. distal to the celiac trunk, but may share a common origin with it in some individuals. Compare the portions of the gastrointestinal tract supplied by the superior and inferior mesenteric arteries. Note that their branches travel through the mesenteries to the intestines and anastomose in the region of the transverse colon.
- Note that the left renal artery emerges from the aorta at a slightly higher level than the right renal artery. This corresponds to the relative levels of the left and right kidneys.
- Follow the course of the testicular (male) and homologous ovarian (female) arteries as they descend. In which sex do they pass through the inguinal canal?
f) The common iliac arteries are the terminal branches of the abdominal aorta. Each common iliac branches into an internal iliac which supplies parietal and visceral structures of the lower abdomen and pelvis and an external iliac which supplies principally the lower extremity. On the models and charts identify the following arteries and state the regions which they supply:
common iliacs external iliacs
internal iliacs femorals
- Which branch of the common iliac is larger in the adult? Why?
- Which branch is larger in the fetus? Why?
- Through what aperture in the abdominal wall does the external iliac artery leave the abdominal cavity and enter the leg (as the femoral artery)?
- Note that the femoral and popliteal arteries are the direct continuations of the external iliac artery in the thigh and knee regions respectively. Below the knee the popliteal branches into the peroneal, posterior tibial, and anterior tibial arteries which supply the leg and foot.
g) The following arteries pass superficial to bony structures providing "pressure points" where each artery may be occluded by surface pressure to control hemorrhages and where an arterial pulse may be palpated or even seen:
brachial artery - the medial aspect of the arm halfway between the shoulder and elbow
radial artery - the lateral wrist, just lateral to the tendon of the flexor carpi radialis
common carotid artery - posteriolateral to the larynx at vertebral level C6
femoral artery - just inferior to the inguinal ligament, 1/3 of the distance from its medial end
posterior tibial artery - posterior half of the inferior border of the medial malleolus
- Try feeling a pulse at each of these points by gently pressing with the tips of the index and middle fingers.
Systemic Veins {FAP Fig 21-26 to 21-30; APL Exercises 18-2, 18-3}
For each vessel of the venous system you should know the location, the major tributaries, and what regions of the body are drained. Veins have thin walls, so that they collapse in cadavers. Veins are generally larger in diameter than the corresponding arteries, reflecting the fact that most of the blood volume at any time is in the veins. Naming of deep veins parallels the naming of the arteries with which they travel. In the extremities there is usually a major deep and one or two major superficial veins corresponding to each major artery. Veins also tend to anastomose, or branch and come back together, more so than do arteries.
a) The tributaries of the superior vena cava drain the head, neck, upper extremities, thorax, and part of the lumbar abdominal wall. On the models and charts locate the following veins and state the regions which they drain:
azygos external jugulars brachials
hemiazygos subclavians cephalics
brachiocephalics axillaries basilics
internal jugulars
- The azygos and hemiazygos drain the thorax and posterior abdominal wall. Note that the hemiazygos drains into the azygos via multiple ladder-like anastomoses, while the azygos drains into the superior vena cava.
- The internal jugular and subclavian are the major tributaries of each brachiocephalic. The smaller external jugular branches from the subclavian. What regions of the head are drained by the internal and external jugular veins?
- The axillary and brachial are the direct extensions of the subclavian vein from the axilla and upper extremity, respectively. The brachial is a deep vein of the arm, while the basilic and cephalic are parallel superficial veins. Note the multiple anastomoses of the veins of the arms.
b) The inferior vena cava drains the abdomen, pelvis, and lower extremities. It penetrates the diaphragm at the vena caval foramen in the central tendon. It runs near the posterior abdominal wall, slightly to the right of the midline, causing its tributaries from the left to be longer than the corresponding tributaries from the right. On the models and chart, locate the following veins and state the regions which they drain:
hepatics common iliacs femorals
renals internal iliacs greater saphenouses
testiculars (or ovarians) external iliacs lesser saphenouses
- Note that the venous return from the spleen and the lower GI tract does not drain directly to the inferior vena cava, but drains via the liver (see below).
- The hepatic veins are the most proximal major tributaries of the inferior vena cava. Why might the hepatic veins be difficult to see in a real human body?
- Note that the left renal vein is substantially longer than the right, and must cross the aorta to reach the inferior vena cava. What is the bilateral asymmetry in the testicular or ovarian vein (into what vessel does it drain on each side)?
- The common, internal, and external iliac veins, as well as the femoral vein, parallel their arterial counterparts. In the lower extremity the femoral vein runs deeply, while the greater and lesser saphenous veins run superficially. The path and size of the saphenous veins make them the vessels most commonly removed and transplanted for coronary artery bypass grafts.
c) The abdominal gastrointestinal viscera, as well as the spleen are drained by a special venous system, the hepatic portal system. This system drains the viscera into the liver, which then drains into the inferior vena cava via the short hepatic veins. On the models and charts locate the following veins and state the regions which they drain:
hepatic portal superior mesenteric
splenic inferior mesenteric
- A venous portal system is a system of veins which drains one set of capillary beds into another. For the hepatic portal system, the distal set of capillary beds is in the gastrointestinal viscera and spleen. Where is the proximal "capillary" bed? Note that the terms "distal" and "proximal" here are relative to the heart.
- What organs are drained by the hepatic portal system? For each organ, state the functional significance of its location "upstream" from the liver. For example, the liver is a primary target organ of the endocrine products of the pancreas, namely insulin and glucagon.
- Note the anatomical relationship between the hepatic portal system and the celiac artery branches . This is a complicated region and should be studied carefully until you are sure that you can distinguish the two systems.
Pulmonary Circulation {FAP Fig 21-18}
The pulmonary arteries have a much lower blood pressure than do the systemic arteries. As a consequence, they have relatively thin walls, and are more difficult distinguish from veins. On the models locate the following pulmonary vessels:
pulmonary trunk pulmonary arteries (2) pulmonary veins (4)
a) The distal ends of these vessels will be studied next week in lung preparations.
b) Note that the lungs have two blood supplies - the pulmonary arteries for alveolar gas exchange and the bronchial arteries (systemic) for the metabolic needs of the lung tissue. Although the lungs are drained by the bronchial veins, a large portion of the blood from the bronchial arteries actually returns to the heart via the pulmonary veins. This blood is deoygenated and constitutes a systemic-pulmonary shunt which slightly lowers the efficiency of the cardiopulmonary system.
Fetal Circulation {FAP Fig 21-32}
Familiarize yourself with the fetal circulation and the changes that occur at birth. For the following fetal vessels and passages know the location, the function, the direction of blood flow, the degree of oxygenation of the blood carried, and the corresponding structure in the adult.
Fetal: Adult:
umbilical arteries --> lateral umbilical ligaments of the bladder
umbilical vein --> ligamentum teres of the liver
ductus venosus --> ligamentum venosum of the liver
ductus arteriosus --> ligamentum arteriosum
foramen ovale --> fossa ovalis
Guide to Histology
Blood Vessels {FAP Fig 21-2; APL Exercise 18-4}
Blood vessels have three tunics (layers) in their walls:
1) Tunica intima - This is the inner layer of all blood vessels and the only layer present in the capillaries. It consists of a simple squamous epithelium (endothelium) and its basement membrane.
2) Tunica media - This middle layer is composed of smooth muscle and elastic C.T. fibers. It is the thickest layer in the arteries. It is bounded by an inner elastic membrane (lamina) in the muscular arteries and arterioles and an outer elastic membrane in the muscular arteries only.
3) Tunica externa (adventitia) - This outer layer consists of dense, irregular C.T. which grades into the surrounding C.T. through which the vessel travels. It is the thickest layer in the veins.
After working through the texts and slides you should be able to distinguish between elastic arteries, muscular arteries, arterioles, veins, and capillaries on the basis of wall structure. and the shape of the lumen. Keep in mind that in any slide of a blood vessel you can gauge how large the vessel is by using the RBCs in the lumen as a measuring stick (7µ diameter).
a) Aorta
The aorta has an extremely thick tunica media, dominated by elastic fibers.
- Identify the tunica intima, tunica media, and adventitia. Note the prominent elastic fibers in the walls of this vessel. In which layer are these fibers found? What is the function of these fibers? Would you expect them to be more numerous in the ascending thoracic aorta or in the abdominal aorta?
- Note the appearance and relative size of the RBCs in the lumen.
b) Other Vessels
Arteries and veins (also arterioles and venules) often travel near each other in through the tissue. Systemic arterial and venous vessels are fairly easy to distinguish, but pulmonary vessels may be more difficult. In the demonstration slides try to do the following:
- Identify the internal and external elastic membranes on one of the larger arteries. Note that only the internal elastic membrane is present on the smaller arterioles. Do veins have either of these elastic membranes?
- Distinguish smaller arteries, arterioles, veins, and venules. Identify the three tunics and note the relative thicknesses in the various vessel types.
- Which vessels have round or oval lumens? Which have irregular-shaped lumens?
Guide to Physiology
Pulse Rate {APL Exercise 19-1}
Arterial pressure waves constituting the "pulse" may be palpated at several body locations where an artery crosses a bony prominence. The radial and carotid pulses are both easy to detect via noninvasive procedures. Since your thumb generates a strong pulse of it own, it is best to use your index and middle finger to palpate the pulse. Work in pairs to compete the following:
1) To palpate the radial pulse, rest your finger tips lightly across the subject's wrist, just below the thenar muscle mass (base of the thumb).
2) To facilitate feeling the carotid pulse, have the subject bend her neck slightly to the opposite side. Rest your finger tips on her neck, just below the angle of the jaw (below the ear) and and slightly in front of the sternocleidoid muscle. NOTE: BE VERY GENTLE IN PALPATING THIS AND DO NOT PALPATE IT BILATERALLY. MAKE SURE THAT THE PATIENT IS LYING DOWN WHEN YOU DO THIS AND STOP IMMEDIATELY IF THE SUBJECT FEELS FAINT.
3) Locate either the radial or carotid pulse and count the number of beats in 15 seconds. Multiply this number by 4 to get the resting heart rate (HR) in beats per minute and record this value below.
4) Have the subject step rapidly up and down on the SoftStep for 60-120 seconds, then immediately measure and record her active heart rate. IF THE SUBJECT FEEL AT ALL FAINT OR UNWELL< HAVE HER STOP AND WIT DOWN.
Resting HR = BPM Active HR = BPM
5) Try to detect the pulse at the following locations. With some of these, you may be more comfortable palpating your own pulse in private.
Upper Limb:
axillary pulse - extreme proximal medial surface of the upper arm
brachial pulse - inside of the upper arm near the elbow
ulnar pulse - medial wrist at the base of the hypothenar muscles (base of the little finger)
Lower Limb
femoral pulse - midpoint of the inguinal ligament
popliteal pulse - extreme posterior distal thigh, behind the (bent) knee
dorsal pedal pulse - proximal top of the foot
medial malleolar pulse - behind the medial maleolus
Head and Neck
facial pulse - over the coranoid process of the mandible even with the corner of the mouth
Blood Pressure (Pneumoplethysmography) {APL Exercise 19-3}
Don't inflate EITHER THE MANUAL OR THE ELECTRONIC blood pressure cuff past 180 mmHg or keep it inflated for more than 60 seconds. Don't put the stethoscope ear pieces into your ears until you have positioned the tambour where you want it.
Manual (Ausculatory) Method
1) Seat the subject and have her pull one shirt/blouse sleeve up as far as possible. Wrap the blood pressure cuff snugly around this arm, with the smooth side of the cuff towards the skin. Secure the Velcro strips. It is important that the subject's arm be relaxed and at her side, so that the blood pressure cuff is level with her heart. (Why?)
2) Place the stethoscope around your neck and press the flat part of the tambour against the inside of the subject's elbow, below the cuff (brachial pulse site). Have the subject hold the gauge with her other hand, so that you can see it. Put the stethoscope tubes in your ears.
3) Now tighten the thumbnut on the bulb and pump up the cuff to about 150 mmHg. Loosen the thumbnut slightly and let the cuff pressure out slowly. At somewhere around 130 - 110 mmHg you should begin to hear a "whooshing" sound. The cuff pressure at which you first hear this sound corresponds to the systolic blood pressure (Ps) - the peak of each pulse pressure cycle. As pressure in the cuff continues to drop, this sound will first become louder, then softer and muffled, then fade out (why?) - generally at 90-70 mmHg. The cuff pressure at this point reflects the diastolic blood pressure (Pd)- the low point in each pulse pressure cycle.
4) Record your blood pressure readings as Ps/Pd. Resting BP = mmHg
While the pressure in the cuff is between the systolic and diastolic values, the gauge needle will make a slight up-tick with each heart beat. Why is this?
5) Check your blood pressure and heart rate readings using an electronic blood pressure meter. To use this device simply turn it on, wait for the display to clear, wrap the cuff around the subject's upper arm, and pump the cuff up to ~180 mmHg. (The newer automatic cuffs are self-inflating). As the cuff automatically deflates its electronic pressure sensor will pick up the transient pulse pressure waves and calculate both blood pressure readings and a pulse rate.
6) Using either set of blood pressure and heart rate readings, calculate the pulse pressure (PP) and estimate cardiac stroke volume (SV) and cardiac output (CO) of the heart by the following formulae:
PP = Ps - Pd PP in mmHg
CO = k x HR x PP where k = 1.7 mL mmHg/beat CO in mL/min
SV = CO/HR SV in mL/beat
Does your subject's measured cardiac output fall roughly within the "standard" range of 4.5 to 6.5 L/min?
7) Have the subject lie down on a table. Using an automated device, measure the blood pressure with her arm hekld vertically above her, then horizontal and level with her heart, then hanging over the side of the table.
BP (below heart) = mmHg
BP (level with heart) = mmHg
BP (above heart) = mmHg
How does the recorded blood pressure vary with height of the cuff site with respect to the heart?
8) If you have time, try taking a reading with the cuff around the right thigh and the stethoscope tambour held behind the knee, and/or with the cuff around the right calf, with the stethoscope tambour held just below the medial malleolus (inner ankle bone).
Capillary Blood Flow Demonstration
The instructor may set up a dissecting microscope demonstration involving the tongue of a pithed frog. Observe the flow of individual blood cells through the smallest capillaries in the tongue. If there is time the instructor may demonstrate the effect of local vasoconstrictive and vasodilatory chemicals.
As an alternative you can try the "Measuring Capillary Refill Time" procedure at the end of APL Exercise 19-2.