Chapter 19 Blood Vessels The circulation of blood William Harvey 1628

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Chapter 19 Blood VesselsThe circulation of blood
(William Harvey 1628)

• Removal of the blood from human cadavers (dead
  bodies) showed that the heart could hold roughly
  two ounces of blood. By calculating the number of
  heartbeats in a day and multiplying this by two
  ounces, he showed that the amount of blood pumped
  was far greater than the amount that the body
  could possibly make. He based this figure on how
  much food and liquids a person could eat during a
  day. To Harvey, this showed that the teaching by
  Galen that the blood was being consumed by the
  organs of the body was false. Blood had to be
  flowing through a 'closed circuit' instead. Even
  though he lacked a microscope, Harvey theorized
  that the arteries and veins were connected to
  each other by capillaries, which would later be
  discovered by Marcello Malpighi some years after
  Harvey's death.

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Chapter 19 Blood VesselsThe circulation of blood
(William Harvey 1628)

• Harvey's lecture notes show that he believed in
  the role of the heart in circulation of blood
  through a closed system as early as 1615. Yet he
  waited 13 years, until 1628, to publish his
  findings. Why did he wait so long? The study and
  practice of medicine as originally taught by
  Galen, was almost sacred at the time Harvey
  lived. No one dared to challenge it. To rebel
  against the teachings of Galen could quickly end
  the career of any doctor. Perhaps this is why
  Harvey waited.

http//www.timelinescience.org/resource/students/b
lood/harvey.htm
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General structure

• Three layers
• Tunica intima
• Tunic media
• Tunic externa

19.1
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Tunica intima

• Endothelium
• Simple squamous epithelium
• Subendothelial layer
• Similar to endocardium

4.4
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Tunica media

• Smooth muscle
• Circularly arranged fibers
• Elastic and collagen fibers
• Thickest layer in arteries

19.1
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Tunica externa

• Adventitia
• Loose connective tissue
• Thickest layer in veins
• Merges with surrounding tissue

19.1
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Arteries

• Elastic (large)
• Muscular (medium)
• Arterioles
• Continuum in reality

19.2abc
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Elastic arteries

• Conducting arteries
• Largest arteries
• Aorta major branches
• High level of elastin in tunica media
• Absorbs pulsations from heart contractions

18.5b
19.2a
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Muscular arteries

• Medium sized arteries
• Supplies blood to organs
• Tunica media controls blood flow
• Most of named arteries

19.1a
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Arterioles

• Smallest arteries
• Tunica media 1-2 layers of smooth muscle fibers
• Controls BP (resistance)
• Supplies capillaries

19.3a
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Capillaries

• Smallest blood vessels
• 8-10 ?m diameter
• Endothelium basal lamina
• Delivers nutrients oxygen to interstitial fluid
• Removes CO2 and waste
• Diffusion and active transport

19.1a
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Types of capillaries

• Continuous
• Fenestrated
• Sinusoidal

19.4abc
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Veins

• Thin walls
• Lower BP
• Venules
• Veins
• Tunica externa thickest
• Valves
• Passive blood flow
• Gravity
• Muscle contraction
• BP

19.1
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Arterial anatomoses

• gt1 artery supplying a capillary bed
• Alternate blood supply
• Collateral circulation
• Example palmar arch

19.7
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Pulmonary circulation

• From right ventricle
• Deoxygenated blood
• Pulmonary trunk
• R L pulmonary arteries
• Respiration in lungs
• Four pulmonary veins
• Oxygenated blood
• L atrium

19.6
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Aorta

• Ascending aorta
• Aortic arch
• Descending aorta
• Thoracic aorta
• Abdominal aorta

19.7
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Ascending aorta

• Arises from L ventricle
• R L coronary arteries

19.8
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Aortic arch

• Posterior to manubrium
• Brachiocephalic trunk
• R common carotid a.
• R subclavian a.
• L common carotid a.
• L subclavian a.

19.8
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Common carotid artery

• Ascends in neck lateral to trachea (palpate)
• At level of larynx branches
• External carotid a.
• Internal carotid a.
• Not shown in anatomical position

19.7,19.9a
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External carotid a.

• Supplies external head
• Scalp, muscles, skin
• Thyroid, tongue
• Skull, oral cavity

19.9a
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Internal carotid a.

• Supplies orbit brain
• Through carotid canal
• Ophthalmic a.
• Anterior cerebral a.
• Middle cerebral a.
• gt 80 of cerebrum
• Foramen lacerum carotid canal

19.9a
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Vertebral a.

• From subclavian a.
• Through transverse foramen C6-C1
• Through foramen magnum
• R L join into basilar a.
• Branches into posterior cerebral as.

19.9a
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Subclavian a. branches

• Thyrocervical trunk
• Muscles of scapula thyroid gland
• Costocervical trunk
• Deep neck muscles
• Internal thoracic a.
• Axillary a.
• Upper limb

19.9a,19.10
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Axillary a.

• Supplies pectoral girdle
• Becomes brachial a.
• Supplies arm
• Radial ulnar a.
• Supply forearm
• Radial extensors
• Ulnar-flexors
• Join to form palmar arches
• Anastomosis
• Digital branches

19.10
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Thoracic aorta

• Mainly supplies thoracic wall (why not the
  contents?)
• (Internal thoracic a.)
• Lateral to sternum
• Anterior posterior intercostal a.

19.10
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Abdominal aorta- 6 Visceral branches

• From diaphragm (T12) to common iliac a. (L4)
• (Inferior phrenic a.)
• Parietal brs.
• To diaphragm

19.11
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Abdominal aorta

• 1. Celiac trunk
• L gastric a.
• Lesser curvature of stomach
• Splenic a.
• Supplies pancreas, stomach, spleen
• Common hepatic a.
• Supplies stomach, pancreas, duodenum, liver

19.12
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Abdominal aorta

• 2. Superior mesenteric a.
• L1
• Travels through mesentery
• Supplies small intestine, ascending part of
  transverse colon

19.13
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Abdominal aorta

• 3. Suprarenal a.
• L1, to adrenal gland
• 4. Renal a.
• L1/L2 to kidney

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Abdominal aorta

• 5. Gonadal a.
• L2
• Testicular a.
• Ovarian a.

19.11
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Abdominal aorta

• 6. Inferior mesenteric a.
• L3
• Supplies transverse descending colon, sigmoid
  colon, rectum

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Abdominal aorta

• Lumbar a.
• Parietal brs.
• Series of pairs
• To posterior abdominal wall

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Common iliac a.

• L4

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Internal iliac a.

• Supplies pelvic contents, gluteal muscles

19.14a
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External iliac a.

• Continuation of common iliac a.
• Descends deep to inguinal ligament

19.15a
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Femoral a.

• Continuation of external iliac a.
• Begins medial to femur
• Twists to posterior femur
• Supplies thigh, femur

19.14a
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Popliteal a.

• Continuation of femoral a.
• Posterior to knee
• Supplies knee

19.14b
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Ant. post. Tibial a.

• Continuations of popliteal a.
• Supplies leg

19.14ab
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Veins

• More variable than arteries
• Often run with arteries

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Major veins

• Superior vena cava
• Brachiocephalic v.
• Subclavian v. and jugular v.
• Inferior vena cava
• Common iliac veins

19.17
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Special Veins

• Dural sinuses drain brain

13.26,13.25a
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Special veins

• Hepatic portal system in abdomen (2 capillary
  beds)

19.22
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Special veins

• Hepatic portal system
• Superior mesenteric v., splenic v., inferior
  mesenteric v.
• Hepatic portal vein
• Liver sinusoids
• Hepatic vein
• Inferior vena cava

19.23