Chapter 20: Circulation

1. Chapter 20:Circulation Blood Vessels and Hemodynamics

2. Blood Flow • Forms a CLOSED system of tubes that carries blood • Most common route • heart  arteries  arterioles  capillaries  tissue  tissue venules  veins • Flow of oxygenated blood= Arteries (largest) to arterioles to capillaries (smallest) and to the tissue • Flow of deoxygenated blood from the tissue- venules (smallest) to veins (largest)

3. Anastomoses • What do you call a prophet's donkey? • Anastomoses: A natural communication between two vessels. • If the anastomoses provides an alternative route for blood flow this is called Collateral circulation • Exercise can increase the body’s creation of collateral circulation, that can prevent tissue necrosis (tissue death)

4. Arteries Anatomy • Artery= (ar= air, ter= to carry)- arteries carry blood that is oxygenated • When dissected after death many arteries don’t contain blood. it was thought that they carried air (ar-) • The wall of artery has three coats or tunics: 1.) The external coat- tunica externa 2.) The middle coat- tunica media 3.) The internal coat- tunica interna

5. Arteries Middle Coat • Tunica Media- thickest layer, smooth Muscle causes the following: 1.) Vasoconstriction- vessels close down, happens with BV trauma to restrict blood flow 2.) Vasodilation- vessels open up, produces warm feeling on skin from exercise

6. Arteries Inner Coat The internal coat- tunica interna • smooth inner layer that repels blood cells & platelets • simple squamous epithelium called: endothelium • Endothelium is a continuous layer of cells that line the entire cardiovascular system (heart and BVs) • so what’s good for epithelium is good for the heart!

7. 4 Red Vessels • 1.) Conducting (elastic) arteries – largest • Tunica media has lots of elastic fibers, example: the aorta helps propel blood away from the heart • pulmonary, aorta and common carotid • expand during systole, recoil during diastole; lessens fluctuations in BP • 2.) Distributing (muscular) arteries • medium sized, tunica media has more smooth muscle fibers, they can vasoconstrict and vasodilate, example radial artery • 3.) Resistance (small) arteries, example: arterioles • arterioles control amount of blood to various organs • 4.) Metarterioles • short vessels connect arterioles to capillaries

8. Capillaries • Capillaries (capillar= hair like)- part of the microcirculation • Primary function: exchange nutrients and waste between blood and tissue cells through the interstitial fluid • Anatomy of capillary: Single layer of epithelium (endothelium) • Metarteriole continues through capillary bed to venule

9. Capillaries- Red meets Blue No cell is more than about two cell diameters from a capillary

10. Capillary- Close Up

11. Veins • Venules (=small veins)-When capillaries unite they form these small veins to carry deoxygenated blood • Veins- as venules get larger and larger they become veins. Same anatomy as arteries but whimpier but they do differ from arteries because they contain one way valves • Venous valves prevent blood back flow • Venous sinuses: veins with thin walls, large lumens, no smooth muscle

12. Venous Return • Venous return- blood going to the heart from the veins • Assisted with: • Heart pumping • Skeletal muscle pump- muscles pump the blood • Respiratory pump- Inhale and abdominal veins cave in pushing blood

13. Principles of Blood Flow • The force that the blood exerts against a vessel wall • Blood flow: amount of blood flow • Perfusion: rate of blood flow to an area, decreased perfusion can cause tissue necrosis • Important for delivery of nutrients and oxygen, and removal of metabolic wastes • Hemodynamics: physical principles of blood flow based on pressure and resistance

14. Blood Pressure • Circulation time- the time it takes for a drop of blood to go from the heart back again. Normal is 1 minute • Blood Pressure- pressure of blood on the walls of the blood vessels. • Pulse pressure = systolic - diastolic • important measure of stress exerted on small arteries • Subtract systolic from diastolic, normal 40 mm Hg

15. Blood Pressure • Normal: young adult: 120/80 mm Hg (mm Mercury) systolic/diastolic • BP rises with age: arteries less distensible • Systolic measures contraction, diastolic relaxation • Blood pressure is measured at the brachial artery of the arm using a sphygmomanometer (sfig-mo-ma-NOM-e-ter) a cuff attached to a column of mercury. • Procedure: Pump the cuff up until the blood stops, then let the pressure lessen the first sound you hear is systolic blood pressure, the last sound will be diastolic blood pressure (you hear no sound if you die)

16. Abnormalities of Blood Pressure • Hypertension • chronic resting BP > 140/90 • can weaken small arteries and cause aneurysms • can effect kidneys • Hypotension • chronic low resting BP • causes: blood loss, dehydration, anemia

17. Regulation of BP and Flow • Cardiovascular center- in the medulla oblongata regulates heart rate and stroke volume • Baroreceptors- found in the barrel of arteries, example: carotid sinus in carotid artery of the neck, aorta • Carotid sinus massage can slow heart rate • Carotid bodies and Aortic bodies- chemical receptors that detect presence of Oxygen, carbon dioxide, hydrogen ion concentration • Hypoxia= low oxygen, acidosis= increased H+, hypercapnia= excess carbon dioxide

18. Carotid body Aortic body Aortic body Chemoreceptors & Baroreceptors

19. Capillary Exchange • The mission of the entire cardiovascular system is to provide for CAPILLARY EXCHANGE so that blood can exchange materials in the interstitial fluid • Capillaries exchange material in three ways: • 1. Diffusion- _____ to ______ concentration • 2. Transcytosis- movement of stuff into vessels by endocytosis and out by exocytosis example: insulin • 3. FIltration and Reabsorption

20. Capillary Exchange - Diffusion • Most important mechanism • Lipid soluble substances • steroid hormones, O2 and CO2diffuse easily • Insoluble substances • glucose and electrolytes must pass through channels, fenestrations or intercellular clefts • Large particles - proteins, held back

21. Capillary Exchange - Filtration and Reabsorption • Opposing forces • blood (hydrostatic) pressure drives fluid out of capillary • Highonarterial end of capillary, lowonvenous end • Fluid filters out of the arterial end of the capillary and osmotically reenters it at the venous end.

22. Causes of Edema • Excess fluid in tissue, some causes: •  Capillary filtration ( capillary BP or permeability) • poor venous return due to: • congestiveheart failure • insufficient muscular activity •  Capillary reabsorption • hypoproteinemia • Obstructed lymphatic drainage

23. Consequences of Edema • Circulatory shock • excess fluid in tissue spaces causes low blood volume and low BP • Tissue necrosis • oxygen delivery and waste removal impaired • Pulmonary edema • suffocation • Cerebral edema • headaches, nausea, seizures and coma

24. Mechanisms of Venous Return • Pressure gradient- generated by the heart pumping • Gravity- head and neck blood “flows downhill” • Skeletal muscle pump in the limbs • Thoracic (respiratory) pump • inhalation - abdominal pressure increases squeezing blood vessels then thoracic cavity expands (pressure drops) and blood flows upward to the heart • Cardiac suction- by the expanding atrial space

25. Skeletal Muscle Pump

26. Venous Return and Physical Activity • Exercise  venous return in many ways • heart beats faster, harder -  CO and BP • vesselsofskeletalmuscles,lungsandheartdilateflow •  respiratory rate  action of thoracic pump •  skeletal muscle pump

27. Shock • Shock is the lack of oxygen to the body • Four types: • Hypovolemic- decreased blood volume, hemorrhage • Cardiogenic- poor heart function, heart attack • Vascular- inappropriate vasodilatation, anaphylactic shockfrom allergies, septic shock from bacteria • Obstructive- obstruction of blood flow, pulmonary embolism

28. Signs of Shock • Sweating • Heart rate rapid, weak rapid pulse • Oral dryness, thirst • Clammy, cool, pale skin • Knocked out mentally, altered mental state

29. Special Circulatory Routes - Brain • Total perfusion kept constant • 4-5 minutes of deprivation causes irreversible brain damage • Responds to changes in BP and chemistry • cerebral arteries: In respose to increased BP the vessels vasodilate and this will cause BP, vasoconstriction causes increased BP if BP has decreased • Ragland’s effect • Postural hypotension- BP lowers when patient stands • Adrenal gland dysfunction

30. TIA • TIA’s - Transient Ischemic Attacks • dizziness, loss of vision, weakness, paralysis, headache or aphasia • Prevention: regular exercsie and stop smoking

31. CVA • A stroke, or cerebrovascular accident (CVA) is a sudden loss of brain function resulting from disruption of the blood supply to a part of the brain • If treatment can be started within 3 hours of the first symptom, then thrombolytic therapy ("clot breaking drug") with Altepase may be considered as an option -Prevention: Regular exercise, no smoking.

32. Major Systemic Arteries • Supplies oxygen and nutrients to all organs

33. Evaluation of Circulation- Pulse • Pulse- feeling the rebound of the arteries by palpation • Normal 70-80 beat per minute (BPM) • Bardycardia- under 60 BPM • Tachycardia- getting excited over velour, over 100 BPM • 9 principal sites: • Temporal artery- head • Facial artery- jaw • Carotid artery- neck • Radial artery- wrist • Brachial artery- elbow • Femoral artery- inferior to groin • Popliteal- behind the knee • Posterior tibial artery- medial ankle • Dorsal pedis artery- back of the pedis

34. Arterial Pressure Points • Some major arteries close to surface -- allows palpation for pulse and serve as pressure points to reduce arterial bleeding

35. Major Branches of the Aorta • Ascending aorta • right & left coronary arteries supply heart • Aortic arch • brachiocephalic • right common carotid supplying right side of head • right subclavian supplying right shoulder & upper limb • left common carotid supplying left side of head • left subclavian supplying shoulder and upper limb • Descending aorta is thoracic aorta above diaphragm and abdominal aorta below diaphragm

36. Major Branches of the Aorta

37. General Artery Circulation- Brain • The vertebral arteries join in the brain to become the basilar artery (which sits on the base of brain stem), this creates the circle of Willis (which circles the optic chiasm) • LEFT NECK: Left common carotid comes off the arch of the aorta, to form the left internal and external carotids which go to the brain • RIGHT NECK: Arch of the aorta gives off the brachiocephalic trunk which gives off the right common carotid, this splits into a right internal and external carotids which go to the brain

38. Arteries of the Upper Limb • Subclavian passes between clavicle & 1st rib • Vessel changes names as passes to different regions • subclavian to axillary to brachial to radial & ulnar • brachial used for BP and radial artery for pulse

39. Arteries of the Thorax

40. GI GI Kidney GI Lower limb Major Branches of Abdominal Aorta

41. Celiac Trunk Branches • Branches of celiac trunk comes off the aorta to supply upper abdominal viscera -- stomach, spleen, liver & pancreas

42. 2 Mesenteric Arteries- Major Supply to the Intestines

43. Arteries of the Lower Limb • The Abdominal Aorta descends • The aorta branches into both legs as the right and left iliac arteries, • At the legs- femoral artery starts by the groin • Popliteal arteries at the knee • At the leg- anterior, posterior tibial arteries, peroneal artery, at the foot- the dorsal pedis artery

44. Major Systemic Veins • Deep veins run parallel to arteries while superficial veins have many anastomoses

45. Veins of Upper Limb • From the arms: radial and ulna veins • To the cubital vein of the elbow • Into the axillary vein • Into the subclavian and then into the • The brachiocephalic vein • And finally into the superior vena cava • Anticubital vein- stab area

46. Veins of Lower Limb • To the legs: Anterior, posterior tibial vein • And saphenous veins into • The popliteal vein and then into • The femoral vein to the • Iliac veins into the inferior vena cava of the abdomen • Into the heart by the inferior vena cava • Saphenous vein-used in heart bypass

47. Clinical • White coat hypertension- high systolic reading due to stress • Publix hypertension/ Home hypotension • Carotid doppler- ultrasound microphone • Arm-leg ratio- comparing arm and leg doppler readings • Vericose veins- Superficial veins