Circulation

I.Basics of Circulatory System

A.Types of Circulatory System

• Some organisms lack

  • But if you’ll need one, 3 components: fluid, vessels, heart

• 2 types:

  • Open Circulatory System

    • Fluid = hemolymph= interstitial fluid

    • Heart contractions- hemolymph → vessels → interconnected sinuses

    • Heart Relations: draw hemolymph back into heart

• Closed Circulatory system

  • Blood: circulatory fluid confined to vessels

  • heart(s): pump blood through branched vessels 

    • High pressure: more efficient, required more E

    • Annelids, cephalopods, vertebrates  

B.Vertebrate Circulation

• Cardiovascular system

  • Involves:

    • Heart: pumps blood

    • Vessels: carry blood

    • Exchange at capillaries

C.Comparison of Vertebrate Circulation

• Fish- Single circulation 

  • Heart: 2 chambers

    • 1 atrium 

    • 1 ventricle 

    • Not very efficient 

• Amphibians: Double Circulation

  • Heart: 3 chambers

    • 2 atria 

    • 1 ventricle

  • Blood Flow: 2 circuit 

    • Pulmocutaneous circuit 

    • Systemic circuit 

    • Some mixing

• Mammals and Birds

  • Heart: 4 chambers

    • 2 atria 

    • 2 ventricles

  • Pulmonary circuit 

  • Systemic Circuit 

  • Completely separate

II.Human Heart

A.Heart Structure

• Pumping Organ, 2- muscular chambers

  • Atria: receive blood from veins

  • Ventricles: pump blood to arteries

  • Pericardium: connective tissue sac, encloses heart.

• 4 valves

  • Flaps of connective tissues: prevent backflow

    • 2 atrioventricular- right, left AV

      • Blood from tissues → atria

      • Blood pressures in atria opens AV valves

      • Ventricular contractions closes AV valves

    • 2 Simulinar

      • Ventricles → arteries

      • Opened by ventricular contraction

      • Pulmonary valve- RV → pulmonary artery

      • Aortic valve - LV → aorta 

      • Heartbeat= valves closing 

B. Heart Contraction

• Autorhythmic- internal ignition- not via AP from CNS

  • Sinoatrial (SA) node: “pacemaker” of heart- small mass of cardiac muscle, RA  

• Impulse from SA node spreads through atria → Atria contract simultaneously 

  • AP reaches atrioventricular (AV) node- autorhythmic cells in septum between RA, RV 

  • 1/10th sec delay at AV node

  • Allows atria to complete contraction before ventricles start

• AP transmitted via bundle branches AV node → heart apex

  • Spreads through Purkinje fibers throughout ventricles 

    • Ventricles contract→

• INSERT DIAGRAM

• Regulation of Heart Rate

  • By NS

  • Baroreceptors: sensory receptors, wall of blood vessels, heart detect delta blood pressure

    • → cardiac centers in medulla → autonomic nerves → SA node

    • Sympathetic: increase heart rate, strength of contraction

    • Parasympathetic: decrease heart rate

  • By endocrine system

    • Stress

    • Adrenal medulla → epinephrine → increase heart rate

    • Temperature 

      • Increase temp → increase rate 

      • Decor. Temp → lower rate

III.Blood Vessels

A.Blood Vessel Structure

• 3 layers:

  • Endothelium: lines lumen (smooth)

  • Smooth muscle: thicker in arteries, thin in  veins

  • Connective tissue: many elastic, collagen fibers

  • Thick walls prevent diffusion

• Arteries 

  • Heart → organs

  • Arteries → arterioles in organs → capillaries 

• Capillaries

  • Microscopic blood vessels in tissues

  • Capillary bed: networks of capillaries, infiltrate all tissues

  • Exchange between blood, tissues

  • Capillary Structure:

    • 2 layers- endothelium and basal lamina

    • At least 1 capillary near every cell in body

    • Only location of exchange between blood, interstitial fluid

• Veins

  • Organs → heart

  • Capillaries → venules → veins

  • Between skeletal muscles- squeezed by muscles

  • 1 way valves prevent backflow 

B.Mechanism of Exchange

• Thin capillary lining: single cell layer

  • Allows diffusion of nutrients, ions, gases, waste

  • Plasma under pressure

    • → some forced into tissue → interstitial fluid

• Interstitial Fluid

  • No RBC’s

  • ~25% of protein content of blood- hypotonic relative to blood

  • Leads to..

    • Fluid exchange between capillaries, tissue- in and out

    • Antagonistic forces- BP, osmotic pressure

      • Arterial end of capillaries: fluid out

      • Verious end of capillaries: fluid in

    • Not all fluid returns (insert diagram) 

IV.Lymphatic System

A.Functions

• Interstitial fluid → blood

• Absorb lipids from SI

• Defend against disease

B.Anatomy

• Contains lymph: watery fluid derived from interstitial fluid

• Truffles through lymph vessels