Blood Vessels And Blood Circulation (Full)

- is a closed system
- formed by blood vessels and 4 heart chambers

• Arteries
  
• Arterioles
  
• Capillaries
  
• Venules
  
• Veins
  

• carry blood away from heart and toward tissues
  
• heart's ventricles pump blood into arteries
  

• small subdivisions of arteries
  
• they divide into capillaries
  

• tiny,thin-walled vessels that allow for exchanges between systems
  
• exchanges occur between blood and body cells and between blood and air in the lung tissues
• capillaries connect arterioles and venules

• small vessels that receive blood from capillaries
• begin its transport back toward heart

• vessels formed by merger of venules
• continue blood's transport until it is returned to heart

• pulmonary circuit
• systemic circuit

• delivers blood to lungs where oxygen is replenished

• pulmonary trunk and its arterial branches
• capillaries in lungs
  
• pulmonary veins
  

carry low oxygen blood from right ventricle to lungs

gases, nutrients and waste are exchanged

carry freshly oxygenated blood to left atrium

low in oxygen content

high in oxygen content

• supplies nutrients and oxygen to all tissues and carries waste materials away from tissue for disposal
  

• aorta
  
• systemic capillaries
  
• systemic veins
  

receives freshly oxygenated blood from left ventricle, then branches into systemic arteries carrying blood to tissue

blood vessels through which materials are exchanged

carry blood low in oxygen towards heart
flows into right atrium through superior/inferior vena cava

• arteries have thick walls to be strong enough to receive blood pumped under pressure from heart's ventricles
• 3 tunics (coats) of arteries

• inner tunic
• middle tunic
• outer tunic

membrane of simple, squamous epithelial cells making up the endothelium
forms a smooth surface over which blood flows easily

thickest layer is made up of smooth (involuntary) muscle

under control of autonomic nervous system

made of supporting connective tissue

• elastic tissue between layers of arterial wall allows vessels to stretch when receiving blood and then return to original size
  
• elastic force propels blood forward between heartbeats, ensuring continuous blood flow

same three layers as arteries however middle smooth muscle tunic is relatively thin in veins
also less elastic tissue

begin with aorta

• largest artery
• 2.5cm in diameter
• receives blood from left ventricle
• ascends from heart, then branches to all organs

1. Ascending aorta
   
2. Aortic arch
3. Thoracic aorta
4. Abdominal aorta

• extends upwards and slightly right from left ventricle
  
• lies within pericardial sac
• contains: left/right coronary arteries

• descends anterior to vertebral column posterior to heart in mediastinum

• longest section of aorta
• beginning at diaphragm and spanning abdominal cavity

• left coronary arteries
• right coronary arteries
  these supply heart muscle

• brachiocephalic artery
  - right subclavian artery
  - right common carotid artery
• left common carotid artery
• left subclavian artery

• short vessel that supplies arm and head on right side
  divides into:
• right subclavian artery
• right common carotid artery

• in brachiocephalic artery
• extends under right clavicle and supplies right arm and part of brain

• in brachiocephalic artery
• supplies right side of neck, head, brain

• extends upward from highest part of aortic arch
• supplies left side of neck and head

• extends under left clavicle
• supplies left arm and part of brain

• branches to chest wall, esophagus, bronchi
• intercostal arteries

• Celiac trunk
  - left gastric artery
  - splenic artery
  - hepatic artery
  
• superior mesenteric artery
• inferior mesenteric artery
• Paired lateral branches
  - phrenic arteries
  - suprarenal arteries
  - renal arteries
  - ovarian and testicular arteries
  - lumbar arteries

subdivides into:

• left gastric artery (to stomach)
• splenic artery (to spleen)
• hepatic artery (to liver)

• large
• blood to most of small intestine/first half of large intestine

• small
• supplies second half of large intestine

1. phrenic arteries - to diaphragm
2. renal arteries - to kidneys
3. ovarian/testicular arteries - to sex glands
4. lumbar arteries - (4 pairs) to musculature of abdominal wall

• abdominal aorta divides into 2 common iliac arteries
  these 2 subdivide into:
• internal iliac artery
• external iliac artery

sends branches to pelvic organs:

• urinary bladder
• rectum
• reproductive organs other than gonads

• continues in thigh as femoral artery
  femoral then becomes deep femoral
  - becomes popliteal at knee
  subdivides into anterior/posterior tibial arteries
• anterior tibial terminates as
  - dorsal pedis at foot
• posterior tibial gives rise to
  - fibular in leg

• external carotid
• internal carotid
• subclavian
  - vertebral artery
  - axillary artery
  - Brachial artery
  - radial artery
  - Ulnar artery

branches to thyroid gland and other structures in head and upper part of neck

travels into head, branches to supply eye, anterior portion of brain

• supplies blood to arm and hand
• 2 branches: vertebral & axillary
• Axillary branches into
  - brachial artery
  - radial artery
  - ulnar artery

• passes through transverse processes of first 6 cervical vertebrae
  
• supplies blood to posterior brain
  

• becomes axillary artery in the armpit
• brachial artery is longest part of axilarry

• section of axillary artery
• in the arm proper
• subdivides into 2 branches: radial & ulnar

• subdivision of brachial artery
• continues down thumb side of forearm and wrist

• subdivision of brachial artery
• extends along little finger side into hand

• communication between two vessels
• 4 examples
  - Cerebral arterial circle (circle of willis)
  - superficial palmar arch
  - mesenteric arch
  - arterial arches

receives blood from 2 internal carotid arteries & basilar artery (formed by union of two vertebral arteries)

formed by union of radial and ulnar arteries in hand

made up of communications between branches of vessels that supply blood to intestinal tract

formed by union of dorsalis pedis artery and second branch of anterior tibial artery

• superficial veins
• deep veins

• cephalic, basilic, median cubital
• saphenous veins

on back of hand, front of elbow

lower extremities

• tend to parallel arteries, usually have same name as corresponding arteries, including:
  - femoral & iliac (internal/external)
  - axillary, brachial (radial, ulnar), subclavian
  
• jugular veins
• brachiocephalic vein (2, but only 1 artery)

• veins of head and neck
• 2 jugular on each side of neck
• internal jugular (larger)
• external jugular (smaller)
• both empty into subclavian vein

receives blood from large veins that drain in the head

drains areas supplied by external carotid artery

on each side, subclavian & internal/external jugular veins join to form brachiocephalic vein

• Venae cavae: 2 large veins receive blood from systemic vessels and empty directly into right atrium
• superior vena cava
• azygos vein (unpaired)
  - chest wall
• Inferior vena cava

• drains veins of chest wall
  
• empties into superior vena cava
• unpaired

• large channel that drains blood low in oxygen but does not have vein's usual tubular structure

• Coronary
• Cranial venous
  - sagittal sinus (superior & inferior) - ends in enlargement called confluence of sinuses
  - straight sinus
  - transverse (lateral) sinuses

spaces between two layers of dura mater

Carries blood from abdominal organs to liver to be processed before returning to heart

• Superior mesenteric vein
• Splenic vein
• Gastric, pancreatic, inferior mesenteric veins
  
• Sinusoids

• largest
• drains blood from proximal portion of intestine
• joined by splenic vein
  
  

• just under liver

• gastric
• pancreatic
• inferior mesenteric
  veins

sinus-like capillaries

Blood exchanges oxygen, carbon dioxide, other substances generated by cells

• exchange medium for circulation physiology
  
• outside blood vessels
• bathes outside of cells

how substances move between cells and capillary blood
3 types:

diffusion, blood pressure, osmotic pressure

• main process of capillary exchange
• no cellular energy needed

• moves material into tissue fluid

• moves material into capillaries

the volume of blood flowing to particular organ can be regulated by changing size of blood vessel supplying that organ

vasomotor center in medulla regulates changes in vessel diameter, sends messages through ANS

increase in blood vessel's internal diameter

decrease in blood vessel's internal diameter

band of smooth muscle encircling entrance to each capillary controlling it's blood supply

- widens to allow more blood to enter when cells need more oxygen

Mechanisms that promote blood's return to heart:

- contraction of skeletal muscles
- valves in veins
- breathing

• ventricular contraction
• wave of increased pressure
• begins at heart, travels to arteries
• influenced by various factors:
  - body size
  - gender
  - age
  - muscular activity
  - emotion

• force exerted by blood against vessel walls
  
• determined by heart's output and resistance to blood flow

refers to total amount of blood that is in vascular system at a given time

adding volume increases blood pressure

volume of blood pumped out of each ventricle in a minute

CO = HR x SV

1. Blood vessel diameter
2. Blood viscosity
3. Blood vessel length
4. Blood vessel compliance
5. Blood vessel elasticity
6. Vasomotor changes
7. Total blood volume

measured in brachial arm artery using sphygmomanometer

• maximum pressure that develops in arteries after heart muscle contraction
  
• normal systolic: 120mmHg
  top number

• lowest pressure measured in arteries after relaxation of heart muscle
• normal diastolic: 80 mmHg
  bottom number

• hypotension (lower than normal)
• hypertension (higher)

hypertension with no apparent medical cause

Stage 1: 140/90mm Hg
Stage 2: 160/100 mm Hg

stage 1: diet, exercise, weight loss
stage 2: drugs added to treatment

• Arteriosclerosis
  - atherosclerosis

• clot formation
• leg cramps, pain, lameness
• headaches, dizziness, mental disorders
• hypertension
• palpitations
• albumin in urine
• ulceration and tissue necrosis
• gangrene

• narrowing of lumen in arteries caused by deposition of fatty material on inner walls
  

Signs: thickening/hardening of blood vessels, loss of elasticity, promotes throbus formation

Symptoms: hypertension, sudden rupture blood vessels, tachycardia, sweating

• Ulceration and tissue necrosis
• results from ischemia
• bacteria invades dead tissues
• S&S: inflamed blackened area, cold peripheries, strong odour, purulent, pain

• Balloon catheterisation
• Bypass grafts
• Stents
• Endarterectomy (removal of vessel's thickened lining)

• bulging sac in blood vessel wall
  - swelling deranges other structures
  - can burst causing death
  - surgery can replace damaged segment

profuse escape of blood from vessels

• formation of blood clot in vessel
  - deep vein thrombosis
  - pulmonary embolism (when embolus reaches lungs)
  - phlebitis
  - thrombophlebitis

• asymptomatic then pain, swelling, deep muscle tenderness, fever, general malaise, elevated white cell count

• inflammation of vein
• if it contributes to clot formation, called thrombophlebitis
  S&S: reddened inflamed area, swelling, warm to touch, pain

• superficial veins that are swollen, distorted and ineffective
  - saphenous veins of lower extremities
  - rectal varicose veins are haemorrhoids

- inadequate blood flow to body tissues

- 4 types

• Cardiogenic - when ventricles fail to pump blood
  
• Septic - result of overwhelming bacterial infection
  
• Hypovolemic - decrease in volume of circulating blood
  
• Anaphylactic - severe allergic reaction