1. Chapter 40 Circulatory System
General Biology II
BSC 2011
Caption: From left to right: erythrocyte, thrombocyte, leukocyte ©Electron Microscopy Facility at The National Cancer Institute at Frederick, edited by: WhatamIdoing, Public Domain

2. Blood Type of connective tissue composed of
Fluid matrix called plasma
Formed elements
Functions of circulating blood
Transportation
Regulation
Protection
Caption: Blood Components ©MesserWoland, ShareAlike

3. Blood plasma 92% water Contains the following solutes
Nutrients, wastes, and hormones
Ions
Na+, Cl–, HCO3, and trace Ca2+, Mg2+, Cu2+, K+, Zn2+
Proteins
Albumin, alpha (a) and beta (b) globulins
Fibrinogen
If removed, plasma is called serum
Caption: two bags of fresh frozen plasma. The bag on the left was obtained from a patient with hypercholesterolemia. ©DiverDave, ShareAlike

4. Formed elements Red blood cells (erythrocytes)
About 5 million per microliter of blood
Hematocrit is the fraction of the total blood volume occupied by red blood cells
Mature mammalian erythrocytes lack nuclei
RBCs of vertebrates contain hemoglobin
Pigment that binds and transports oxygen
Caption: Red blood cells as seen at 50x magnification. The 18th Medical Support Squadron laboratory at Kadena Air Base, Japan, performs numerous tests on blood, bacteria, urine and stool samples in an effort to enhance patient care. (U.S. Air Force photo/Staff Sgt. Christopher Hummel) © U.S. Air Force photo/Staff Sgt. Christopher Hummel, Public Domain

5. Formed elements White blood cells (leukocytes)
Less than 1% of blood cells
Larger than erythrocytes and have nuclei
Can migrate out of capillaries into tissue fluid
Types
Granular leukocytes
Neutrophils, eosinophils, and basophils
Agranular leukocytes
Monocytes and lymphocytes
Caption: White Blood Cells © Blausen.com staff, ShareAlike

6. Formed elements Platelets
Cell fragments that pinch off from larger cells in the bone marrow
Function in the formation of blood clots
An injury to a blood vessel initiates the process of hemostasis. Blood clotting involves three steps. First, vascular spasm constricts the flow of blood. Next, a platelet plug forms to temporarily seal small openings in the vessel. Coagulation then enables the repair of the vessel wall once the leakage of blood has stopped (credit a: Kevin MacKenzie). Download for free at

7. Formed elements All develop from pluripotent stem cells
Hematopoiesis is blood cell production
Occurs in the bone marrow
Caption: This diagram shows the hematopoiesis as it occurs in humans. ©A. Rad, ShareAlike

8. Invertebrate Circulatory Systems
Sponges, cnidarians, and nematodes lack a separate circulatory system
Sponges circulate water using many incurrent pores and one excurrent pore
Hydra circulate water through a gastrovascular cavity (also for digestion)
Nematodes are thin enough that the digestive tract can also be used as a circulatory system
Caption: Ancylostoma duodenale ©Fernandolive, Public Domain
Caption: Hydras ©Stephen Friedt, ShareAlike
Caption: Porifera body structure (light blue is water flow) ©Philcha, ShareAlike

9. Invertebrate Circulatory Systems
Larger animals require a separate circulatory system for nutrient and waste transport
Open circulatory system
No distinction between circulating and extracellular fluid
Fluid called hemolymph
Closed circulatory system
Distinct circulatory fluid enclosed in blood vessels and transported away from and back to the heart
In (a) closed circulatory systems, the heart pumps blood through vessels that are separate from the interstitial fluid of the body. Most vertebrates and some invertebrates, like this annelid earthworm, have a closed circulatory system. In (b) open circulatory systems, a fluid called hemolymph is pumped through a blood vessel that empties into the body cavity. Hemolymph returns to the blood vessel through openings called ostia. Arthropods like this bee and most mollusks have open circulatory systems.
Download for free at

10. Vertebrate Circulatory Systems
Fishes
Evolved a true chamber-pump heart
Have a 2 chambered heart
Blood is pumped through the gills, and then to the rest of the body
Fish have the simplest circulatory systems of the vertebrates: blood flows unidirectionally from the two-chambered heart through the gills and then the rest of the body.
Download for free at

11. Vertebrate Circulatory Systems
Amphibians
Advent of lungs required a second pumping circuit, or double circulation
Pulmonary circulation moves blood between the heart and lungs
Systemic circulation moves blood between the heart and the rest of the body
Amphibians have two circulatory routes: one for oxygenation of the blood through the lungs and skin, and the other to take oxygen to the rest of the body. The blood is pumped from a three-chambered heart with two atria and a single ventricle.
Download for free at

12. Vertebrate Circulatory Systems
Amphibian heart
3-chambered heart
2 atria and 1 ventricle
Incomplete seperation of two circuits
Amphibians obtain additional oxygen through their skin
Reptiles have a septum that partially subdivides the ventricle, further reducing mixing of blood
Reptiles also have two circulatory routes; however, blood is only oxygenated through the lungs. The heart is three chambered, but the ventricles are partially separated so some mixing of oxygenated and deoxygenated blood occurs except in crocodilians and birds.
Download for free at

13. Vertebrate Circulatory Systems
Mammals, birds, and crocodilians
4-chambered heart
2 separate atria and 2 separate ventricles
Right atrium receives deoxygenated blood from the body and delivers it to the right ventricle, which pumps it to the lungs
Left atrium receives oxygenated blood from the lungs and delivers it to the left ventricle, which pumps it to rest of the body
Mammals and birds have the most efficient heart with four chambers that completely separate the oxygenated and deoxygenated blood; it pumps only oxygenated blood through the body and deoxygenated blood to the lungs.
Download for free at

14. The Cardiac Cycle Heart has two pairs of valves
Atrioventricular (AV) valves
Maintain unidirectional blood flow between atria and ventricles
Tricuspid valve = On the right
Bicuspid, or mitral, valve = On the left
Semilunar valves
Ensure one-way flow out of the ventricles to the vessels
Pulmonary valve located at the exit of the right ventricle
Aortic valve located at the exit of the left ventricle
Caption: Human Heart Pumping ©Clker-Free-Vector-Images, Public Domain

15. The Cardiac Cycle
Valves open and close as the heart goes through the cardiac cycle
Ventricles relaxed and filling (diastole)
Ventricles contracted and pumping (systole)
“Lub-dub” sounds heard with stethoscope
Lub – AV valves closing
Dub – closing of semilunar valves

16. The Cardiac Cycle Heart contains “self-excitable” autorhythmic fibers
Most important is the sinoatrial (SA) node
Located in wall of right atrium
Acts as pacemaker
Autonomic nervous system can modulate rate
Specialized conducting components of the heart include the sinoatrial node, the internodal pathways, the atrioventricular node, the atrioventricular bundle, the right and left bundle branches, and the Purkinje fibers.
Download for free at

17. The Cardiac Cycle Each SA depolarization transmitted
To left atrium
To right atrium and atrioventricular (AV) node
AV node is only pathway for conduction to ventricles
Spreads through atrioventricular bundle
Purkinje fibers
Directly stimulate the myocardial cells of both ventricles to contract
Specialized conducting components of the heart include the sinoatrial node, the internodal pathways, the atrioventricular node, the atrioventricular bundle, the right and left bundle branches, and the Purkinje fibers.
Download for free at

18. The Cardiac Cycle
Electrical activity can be recorded on an electrocardiogram (ECG or EKG)
Caption: Schematic diagram of normal sinus rhythm for a human heart as seen on ECG ©Anthony Atkielski, Public Domain

19. Characteristics of Blood Vessels
Blood leaves heart through the arteries
Arterioles are the finest, microscopic branches of the arterial tree
Blood from arterioles enters capillaries
Blood is collected into venules, which lead to larger vessels, veins
Veins carry blood back to heart

20. Characteristics of Blood Vessels
Arteries and veins are composed of four tissue layers
Endothelium, elastic fibers, smooth muscle, and connective tissue
Walls too thick for exchange of materials across the wall
Capillaries are composed of only a single layer of endothelial cells
Allow rapid exchange of gases and metabolites between blood and body cells
Caption: Diagram of arteries, veins and capillaries ©Kelvinsong, ShareAlike

21. Characteristics of Blood Vessels
Arteries and arterioles
Larger arteries contain more elastic fibers in their walls than other blood vessels
Recoil each time they receive blood from the heart
Contraction of the smooth muscle layer of the arterioles results in vasoconstriction
Greatly increases resistance and decreases flow
Chronic vasoconstriction can result in hypertension
Relaxation of the smooth muscle layer results in vasodilation
Decreasing resistance and increasing blood flow to an organ

22. Characteristics of Blood Vessels
Veins and venules
Thinner layer of smooth muscles than arteries
Venous pump helps return blood to heart
Skeletal muscle contractions and one-way venous valves
The contraction of skeletal muscles surrounding a vein compresses the blood and increases the pressure in that area. This action forces blood closer to the heart where venous pressure is lower. Note the importance of the one-way valves to assure that blood flows only in the proper direction. Download for free at

23. The Lymphatic System
Significant amount of water and solutes in the blood plasma filter through the walls of the capillaries to form the interstitial (tissue) fluid
Most fluid leaves at the arteriole end of the capillary and returns at the venule end
Fluid that does not return to capillaries is returned to circulation by the lymphatic system
Net filtration occurs near the arterial end of the capillary since capillary hydrostatic pressure (CHP) is greater than blood colloidal osmotic pressure (BCOP). There is no net movement of fluid near the midpoint since CHP = BCOP. Net reabsorption occurs near the venous end since BCOP is greater than C. Download for free at

24. The Lymphatic System
Consists of lymphatic capillaries, lymphatic vessels, lymph nodes, and lymphatic organs (spleen and thymus)
Excess fluid in the tissues drains into blind-ended lymph capillaries
Lymph passes into progressively larger vessels with one-way valves
Eventually drains into subclavian veins
Lymphatic capillaries are interlaced with the arterioles and venules of the cardiovascular system. Collagen fibers anchor a lymphatic capillary in the tissue (inset). Interstitial fluid slips through spaces between the overlapping endothelial cells that compose the lymphatic capillary. Download for free at
Lymphatic vessels in the arms and legs convey lymph to the larger lymphatic vessels in the torso Download for free at

25. Cardiovascular Diseases
Leading cause of death in the United States
Atherosclerosis
Accumulation of fatty material within arteries
Impedes blood flow
Arteriosclerosis
Arterial hardening due to calcium deposition
(a) Atherosclerosis can result from plaques formed by the buildup of fatty, calcified deposits in an artery. (b) Plaques can also take other forms, as shown in this micrograph of a coronary artery that has a buildup of connective tissue within the artery wall. LM × 40. (Micrograph provided by the Regents of University of Michigan Medical School © 2012). Download for free at

26. Blood Flow and Blood Pressure
Blood Pressure measured as systole/diastole
Systole – ventricle contraction
Diastole – ventricle relaxation
Increases with blood volume
Blood volume is regulated by four hormones
Antidiuretic hormone (ADH)
Aldosterone – encourages kidney to excrete postassium and retain sodium
Atrial natriuretic hormone – increases sodium excretion and decreases blood pressure
Nitric oxide (NO) - vasodialator