Warm-Up 4/29 What is the function of the sinoatrial node? What does the QRS complex of an EKG represent? What two vessels are the semi-lunar valves located in?

External Parts Enclosed by membrane called pericardium Double layered sac Contains pericardial fluid to reduce the friction of the beating heart

Pericardium Layers Visceral pericardium Parietal pericardium Inner membrane Surrounds heart Attached to myocardium Parietal pericardium Outer membrane Anchors heart to sternum and diaphragm Parietal pericardium

Layers of heart walls Three-layered wall Pericardium – outer layer of fibrous tissue Myocardium – middle layer of thick muscle Endocardium – inner layer of epithelial cells

Chordae tendineae “heart strings” Attach to AV valves Anchor flaps on valves in closed position when needed

6 Pulmonary valve Aortic valve Opening of left coronary artery Tricuspid valve Mitral valve Fibrous skeleton Posterior 6

The Blood Vessels The cardiovascular system has three types of blood vessels: Arteries (and arterioles) – carry blood away from the heart Capillaries – where nutrient and gas exchange occur Veins (and venules) – carry blood toward the heart. Blood vessels require oxygen and nutrients, so larger ones have blood vessels in their walls.

The Arteries Thick strong wall (three layers or tunics) Endothelial lining Middle layer of smooth muscle and elastic tissue Outer layer of connective tissue The largest artery is the aorta. The smooth muscle of the middle layer can constrict to regulate blood flow and blood pressure. Arterioles are smaller than arteries have have a thinner middle and outer layers Arterioles can constrict or dilate, changing blood pressure and flow into capillaries. The inner layer of an artery wall is a simple squamous epithelium called endothelium with a connective tissue basement membrane with elastic fibers. The outer layer is fibrous connective tissue near the middle layer, but it becomes loose connective tissue at its periphery.

Arteriole Smooth muscle cell Endothelium Precapillary sphincter Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Arteriole Smooth muscle cell Endothelium Precapillary sphincter Capillary 9

The Capillaries Capillaries have walls only one cell thick to allow exchange of gases and nutrients with tissue fluid. Capillaries have one-cell-thick walls composed only of endothelium with a basement membrane. Capillaries form vast networks with a total surface area of 6,000 square meters in humans.

Anatomy of a capillary bed A capillary bed forms a maze of capillary vessels that lies between an arteriole and a venule. When sphincter muscles are relaxed, the capillary bed is open, and blood flows through the capillaries. When sphincter muscles are contracted, blood flows through a shunt that carries blood directly from an arteriole to a venule. As blood passes through a capillary in the tissues, it gives up its oxygen (O2). Therefore, blood goes from being O2-rich in the arteriole (red color) to being O2-poor in the vein (blue color).

© Don. W. Fawcett/Visuals Unlimited Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Arteriole Capillary Venule © Don. W. Fawcett/Visuals Unlimited

The Veins Venules drain blood from capillaries, then join to form veins that take blood to the heart. Veins often have valves that prevent the backward flow of blood when closed.

Blood vessels The walls of arteries and veins have three layers. The inner layer is composed largely of endothelium, with a basement membrane that has elastic fibers; the middle layer is smooth muscle tissue; the outer layer is connective tissue (largely collagen fibers). Arteries (on left) have a thicker wall than veins because they have a larger middle layer than veins. Capillary walls (center) are one-cell-thick endothelium. Veins (on right) are larger in diameter than arteries, so that collectively veins have a larger holding capacity than arteries.

Toward heart

Varicose veins

What causes varicose veins? High blood pressure inside your superficial leg veins causes varicose veins. Factors that can increase your risk for varicose veins include having a family history of varicose veins, being overweight, not exercising enough, smoking, standing or sitting for long periods of time

Treatment often involves destroying the vein

VIDEOS!

TODAY! If you have not finished labeling the events on each image of your flip book you need to complete that. Once you have completed that show that to Mr. Baker and he will give you the first portion of the case study. Once you are done with that check with Mr. Baker and show him the work and he will give you the second portion. Complete the second portion and show it to Mr. Baker and he will give you the third portion of the case study. THE THIRD PORTION OF THE CASE STUDY IS DUE TO Mr. BAKER BY END OF CLASS THURSDAY!

No Warm-Up! Get into groups of 4-5

Using your group members and any available props, you will act out the journey of a drop of blood through the circulatory system. On this journey you will need to describe the events of the cardiac cycle as they happen. This may be a skit, a dance, mime, anything as long as it is some physically active and accurate representation. Include all events we’ve discussed, including arteries, arterioles, capillaries, venules and veins in your presentation as well. You will have 45min to create. Then you will present to the class.

In your groups you will be acting out the path of a drop of blood through the body. You must create and perform a skit, dance, mime, some physically active representation of the path of a drop of blood through the body and the events of the cardiac cycle. Include all events on your 1-22 slips of paper, but include arteries, arterioles, capillaries, venules and veins in your presentation as well. You will have 1 hour to create. Then you will present to the class.