Unit II: TransportCardiovascular System II

Chapter 18: pp 657-671

Chapter 17: pp 595-619

• Amount ejected by ventricle in 1 minute

• Cardiac reserve: with fitness, with disease

Maximum for trained athletesexercising at peak levels

Normal rangeof cardiacoutput duringheavy exercise

Average resting cardiac output

Some forms ofheart failure

Cardiacoutput

(L/min)

0

5

10

15

20

25

30

35

40

HR: 75 beats/min SV: 80 mL/beat CO: 6000 mL/min=x

Cardiac Output (CO)

Cardiac Output (CO)

Body temperature

ANSHormones

Muscular contractions

Blood volume

Peripheral blood flow

Venous return ↑ = ↑ SV

EDV

Influences the efficiency of contractions

ESV

↑ Filling time = ↑ ESV

↑ afterload = ↓ pumping efficiencyand ↑ESV

Vasodilation

Vasoconstriction

↑ contractility = ↓ ESV

ANS Hormones

STROKE VOLUME (SV) = EDV – ESVHEART RATE (HR)

CARDIAC OUTPUT (CO) = HR x SV

Factors affecting heart rate (HR) Factors affecting stroke volume (SV)

Heart Rate

• Pulse:

– infants have HR of 120 bpm or more

– young adult females avg. 72 - 80 bpm

– young adult males avg. 64 to 72 bpm

– HR rises again in the elderly

• Tachycardia:

– stress, anxiety, drugs, heart disease or body temp.

• Bradycardia:

– in sleep and endurance trained athletes

Bradycardia Tachycardia

Normal range ofresting heart

rates

60 bpm 100 bpm

• Tunica interna: repels blood cells and platelets

– simple squamous endothelium overlying a basement membrane

• Tunica media: smooth muscle, collagen, elastic tissue

• Tunica externa: loose connective tissue

Tunica externa

Tunica media

Tunica intima

Endothelium

Smooth muscle

Vein

The structureof the wall ofa vein

LM x 60

Vein

Artery

Anatomy of Blood Vessels

Arteries

3 Categories by Size:• Conducting (elastic) arteries

– pulmonary, aorta & common carotid

• Distributing (muscular) arteries– Brachial, femoral and splenic

• Resistance (small) arteries

– Arterioles

Capillaries

Arterioles

Distributing/Muscular Arteries

Conducting/Elastic Arteries

Internal elastic layerTunica intimaTunica mediaTunica externa

Tunica intimaTunica mediaTunica externa

Smooth muscle cellsEndothelium

Endothelial cells

Basal lamina

Veins

• thinner tunica media

• 3 Categories by Size:

– Small veins

• venules

– Medium veins

• Radial, ulnar veins

• valves prevent backflow

– Large veins

– Vena cava, pulmonary, jugular

Large Veins

Medium-sized Veins

Venules

Capillaries

Basal lamina

Endothelial cells

Pores

EndotheliumTunica externa

Tunica externaTunica mediaTunica intima

Tunica externaTunica mediaTunica intima

Filtration Predominates

No Net Movement

Reabsorption Predominates

24 L/day 20.4 L/day

ArterioleVenule KEY

CHP (Capillaryhydrostatic pressure)BCOP (Blood colloidosmotic pressure)NFP (Net filtrationpressure)

35 25 25 25 2518mm mmmmmmmmmmHg HgHgHgHgHg

NFP = +10 mm Hg NFP = 0

NFP = –7 mm Hg

Capillary

CHP > BCOP CHP = BCOP BCOP > CHP

Capillaries• Smallest blood vessels

• Only vessels that allow exchange of materials

• Anatomy:

– simple squamous endothelium with basement membrane

– walls: 0.2-0.4 µm thick; lumen: 5-9 µm diameter

Capillary Beds

•Metarterioles

– connect arterioles to capillaries

•Thoroughfare channel

– connect capillaries to venule

•Perfusion

– precapillary sphincter

Gap betweenadjacent cells

Basal laminaEndothelial cell

Nucleus

Types of Capillaries

• Continuous – (4nm)

– endothelial cells have tight junctions

• Fenestrated – (20-100nm)

– organs that require rapid absorption or filtration

– Ex. kidneys, small intestine

• Sinusoids – (30-40nm)

Basal laminaEndothelial cell

Nucleus

Circulatory Routes• Most common route

– heart arteries arterioles capillaries venules veins heart

• Portal system

• hypothalamus – pituitary

• in kidneys

• intestines – liver

• Anastomoses

• Arteriovenous anastomosis

• Ears, fingers, toes, palms

Blood Pressure

• Force that blood exerts against a vessel wall

• Measured at brachial artery of arm

• Systolic pressure and diastolic pressure

• Normal value, young adult: 120/75 mm Hg

Blood Pressure

• Importance of arterial elasticity

– expansion and recoil maintains steady flow of blood throughout cardiac cycle, smoothes out pressure fluctuations and stress on small arteries

• BP rises with age: arteries less distensible

Leastresistance,greatest flowat center

Greatest resistance,slowest flow near surfaces

Internal surface area = 2

Internal surface area = 1

Resistance to flow = 1Flow = 1

Resistance to flow = 2Flow = ½

Blood Pressure

BP determined by:

• cardiac output

• blood volume

• peripheral resistance

– Blood viscosity

– Vessel length

– Vessel radius (vasomotion)

R. Common carotidR. Subclavian

Brachiocephalictrunk

AxillaryAscending aorta

Brachial

Radial

Ulnar

Femoral

Aortic archDescending aortaDiaphragm

Renal

Common iliac

Arteries

Veins

External jugularInternal jugularSubclavian

Brachiocephalic

AxillaryBrachial

Radial

Ulnar

Femoral

Superior vena cava

Diaphragm

Inferior vena cavaRenal

Common iliac

Fetal Development and Circulation

• Fetus = from 8 weeks until birth

• Fetal circulation– umbilical-placental circuit– circulatory shunts

• ductus venosus• foramen ovale• ductus arteriosus

Foramen ovale

Ductus arteriosus

Pulmonarytrunk

Inferior vena cava

Ductus venosus

Umbilical arteries

Umbilical vein

Umbilicalcord

Placenta

Aorta

Liver

Blood Circulation Before Birth