Objectives
- Name the types, subtypes, and major functions of each circulatory system component.
- Name the three tunics that make up the walls of circulatory system components and know the tissue type in each tunic.
- Compare circulatory system components in terms of size and wall structure.
- Relate the wall structure of each circulatory system component to its major functions.
- Describe the heart’s impulse-generating and impulse-conducting system in terms of structure, function, location, and how the impulse is conveyed to the cardiac muscle fibers.
- Recognize the vessel types present in a micrograph and identify their structural components.
- Distinguish between cardiac muscle and Purkinje fibers, and identify the endocardium, myocardium, epicardium, and valves in micrographs of the heart.
- Predict the functional consequences of a structural defect in any circulatory system component.
MAX-Yield™ Study Questions
5. Name two points of functional contact between the blood and lymphatic vascular systems. How does fluid from the blood vascular system enter the lymphatic vascular system? How does lymph enter the blood vascular system (IV; V.C)?
6. Name the three layers (tunics) that comprise blood vessel walls and the tissues characteristic of each (I.C.1–3).
8. Name the four major types of blood capillaries (II.A.3.a–c) and compare them in terms of diameter and the presence of fenestrae, a continuous basal lamina, and phagocytic cells in and around the capillary wall.
9. Describe three ways in which substances (e.g., proteins, fluid, salts) may be transported across capillary walls (II.A.4).
10. Describe the action of capillary endothelial cells on angiotensin I, bradykinin, serotonin, prostaglandins, norepinephrine, thrombin, thrombus formation, and lipoproteins (II.A.2.a).
11. List the three main classes of arteries according to diameter (Table 11–1) and compare them in terms of their relative abundance (II.A.1); the composition of their tunica intima, media, and adventitia; and their function.
12. Describe the carotid and aortic bodies (II.E) in terms of location, receptor class, and function.
14. List the three main classes of veins according to their diameter (Table 11–2) and compare them in terms of their relative abundance (II.A.1); the composition of their tunica intima, media, and adventitia; and their function.
Valves
Internal elastic lamina
Elastin
Relative tunica media thickness
Smooth muscle in tunica adventitia
Relative tunica adventitia thickness
Relative total wall thickness
Vasa vasorum (II.H)
17. Name the heart’s three tunics, the blood vessel tunic to which each corresponds, and the basic tissue type in each (III.B.1–3). Which is the thickest tunic?
20. List, in order, the components of the heart’s impulse-conducting system through which an electric stimulus must pass to cause contraction of the ventricular myocardium (III.E). Hint: Include the cardiac muscle cells themselves.
21. Compare Purkinje fibers (III.E.5) and typical cardiac muscle cells (III.B.2.a, b and E.6) in terms of their diameter, conduction velocity, myofilament amount and distribution, and intercalated disks.
22. In a section of the heart, would you find Purkinje fibers closer to the epicardium or endocardium (III.B.1)?
25. Compare lymphatic capillaries with blood capillaries (V.B) in terms of their epithelial lining, fenestrations, zonulae occludens, and basal laminae.
Synopsis
The circulatory system is responsible for the transport and homeostatic distribution of oxygen, nutrients, wastes, body fluids and solutes, body heat, and immune system components.
The cardiovascular system is a closed system of tubes, through which the blood circulates with the aid of an in-line pump. It has four main components: the heart, a muscular pump; the arteries, which carry blood from the heart to the tissues; the veins, which return blood from the tissues to the heart; and the capillaries, which intervene between the arteries and veins, allowing an exchange of nutrients, oxygen, and waste products between the blood and other tissues.
The lymphatic vascular system comprises another set of vessels, in which lymph (excess tissue fluid, cellular debris, and lymphocytes) moves in only one direction (toward the junction of the lymph vessels with the large veins in the neck). This system lacks a separate pump and includes three vessel types. Lymphatic capillaries are blind-ended endothelial tubes that collect lymph from the intercellular spaces. Lymphatic vessels collect lymph from lymphatic capillaries. Lymphatic ducts collect lymph from smaller lymphatic vessels and empty into the jugular and subclavian veins.
Circulatory system components are hollow, with an open channel, or lumen, at their center. They are described in terms of their wall structure (II). Vessel walls typically have three concentric layers or tunics. In lymphatic vessels, tunic borders are less distinct than those in blood vessels. Local weakening of vessel walls as a result of embryonic defects, disease, or lesions may cause a thin-walled outpocketing, or aneurysm, that may rupture, causing a hemorrhage.
The tunica intima is the inner layer and borders the lumen. The intima of arteries and veins and that of the heart (the endocardium) are virtually identical. It consists of endothelium (a simple squamous epithelium bordering the lumen, underlaid by a thin basal lamina) and subendothelial connective tissue. Capillaries consist solely of endothelium. In arteries, the intima is separated from the tunica media by a fenestrated layer of elastin, the internal elastic lamina.
The tunica media, or middle layer, consists mainly of circumferential vascular smooth muscle fibers. Arteries generally have a thicker media (more muscle and elastic fibers) than do veins or lymphatic vessels. Medium-sized arteries often exhibit an external elastic lamina between the media and the tunica adventitia. The heart’s media (myocardium) is much thicker than that of the largest artery (aorta) and consists of cardiac muscle.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
