CP 3 - Histology handout and lecture (FINAL) Flashcards
what the divisions of the Cardiovascular system?
A. Pulmonary circulation to the lungs versus systemic circulation to the rest of the body.
B. Lymphatic system that drains excess interstitial fluid back into the circulation.
which vessels are elastic?
arteries
What vessels does blood flow through?
Blood flows from heart to large elastic arteries to muscular or distributing arteries to arterioles to capillaries to venules to small to medium sized veins to large veins and back to heart.
What are some deviations from the general circulatory plan?
B. Deviations from this general circulatory plan.
1. Portal systems of blood flow.
2. Arteriovenous anastomoses: Blood bypasses capillaries and passes from arterioles to venules. Examples found in dermis of skin of hands and feet.
What are 2 examples of portal systems of flow?
a. Example: Hepatic portal system: Hepatic portal vein deliveries materials picked up in capillary plexus of gut to the liver capillary plexus (i.e. liver sinusoids).
b. Example: Hypophyseal portal system: Neurosecretory material picked up in capillary plexus in the hypothalamus drain by way of portal vein down pituitary stalk to capillary plexus in adenohypophysis.
What is one thing capillaries are involved in?
Involved in exchange of gases, metabolic waste, nutrients, and hormones.
What are 3 three major types of capillaries
Continuous Capillaries:
Fenestrated capillaries:
True Sinusoids:
Fenestrated Sinusoids:
Describe continuous capillaries
- Continuous capillaries (Figure 2): The most common type of capillary. Continuous capillaries are found in muscle connective tissue, CNS, etc.
a. Luminal diameter of 7-9 microns. Just large enough for a RBC to squeeze through.
b. Very thin endothelial wall surrounded by a basal lamina. Endothelial nuclei bulge into lumen. Scattered mitochondria, ribosomes, Golgi, microtubules and microfilaments. Most pronounced ultrastructural feature is numerous pinocytotic pits and vesicles (approximately 80 nanometers in diameter).
c. Pericytes (perivascular cells): Function is not clear. May be able to differentiate into smooth muscle or phagocytic cells when the need arises.
Describe Fenestrated capillaries
Fenestrated capillaries (Figure 2).
a. Numerous pores in lining endothelium. These pores are spanned by a thin diaphragm (Except in kidney glomerulus where pores are open). b. Examples: found in intestines and kidneys-
describe True sinusoids
True sinusoids
a. Usually large (up to 30-40 microns in diameter) with irregularly shaped lumens.
b. There may be prominent intercellular spaces between endothelial cells and fenestrations in the endothelium.
c. The basal lamina may be missing or discontinuous.
d. Examples: Found in liver, spleen, and bone marrow.
Fenestrated sinusoids
Large lumen fenestrated capillaries. Examples: Found in adenohypophysis (pituitary gland) and adrenal gland.
What are 4 ways that materials flow across the capillary?
Describe each
MECHANISMS OF EXCHANGE OF MATERIALS ACROSS THE CAPILLARY WALL
A. Diffusion: Gases and lipid soluble substances can pass across the plasmalemma.
B. Filtration: Hydrostatic versus oncotic pressures causing the movement of water and small molecules between the “leaky tight junctions.”
C. Vesicular transport: (transcytosis) Main mechanism: for movement of large molecules (> 9 nanometers, e.g. plasma proteins) across the endothelium by way of pinocytotic pits and vesicles. -Not energy dependent. (gold particles example)
D. Transendothelial channels: Formed by the fusion of vesicles and spanned by diaphragms. For transport of molecules < 9 nanometers in size.
BONUS: Open pores or gaps in sinusoids
What are the layers of large vessels?
name some features
A. Tunica intima: Endothelium and subendothelial connective tissue (internal elastic lamina surround this: looks like swiss cheese in the diagram)
B. Tunica Media: Smooth muscle (elastic fibers may also be present; External elastic Lamina surrounds this)
C. Tunica Adventitia: Connective tissue -Vasa vasorum - nerves
D. Elastic Lamina: Internal and external.
What does the tunica media of the aorta contain?
numerous elastic fibers
What are the basic differences between arteries and veins
A. Usually run along side of each other (i.e. artery has a “companion vein”).
B. Veins have less muscle, more connective tissue, less elastic tissue, larger lumens, and valves (in the extremities).
Describe the STRUCTURE OF THE HEART
The heart can be subdivided into three layers:
An endocardium (homologous to tunica intima);
a myocardium (homologous to tunica media);
an epicardium (homologous to tunica adventitia).
Describe the endocardium
- Lines all internal surfaces of the heart, and is continuous with the tunica intima of blood vessels.
- The endocardium consists of an endothelium and an underlying thin layer of connective tissue. Under the endocardium is a thicker layer of subendocardial connective tissue.
Describe the Myocardium
Myocardium: Forms the main mass of the heart and consists of cardiac muscle. The myocardium is thin in the atria, and much thicker in the ventricles. The muscle fibers within the myocardium are attached to the “fibrous skeleton II of the heart.” The fibrous skeleton consists of dense fibrous connective tissue.
Describe the Epicardium (visceral pericardium):
Epicardium (visceral pericardium): Forms the outermost covering of the heart.
a. A Subepicardial region consisting of loose connective tissue, blood vessels and nervous tissue lies under the epicardium. b. Parietal layer of pericardium: Consists of a serosal layer with mesothelial surface facing the epicardium. c. Pericardial cavity: A potential space between the visceral and parietal pericardium which in health contains up to 50 mL. of fluid distributed as a thin film between the apposed mesothelial surfaces.
What are lymph vessels and what is their function?
The lymphatic vessels represent a drainage system whereby fluid and plasma protein which has collected in the interstitium is returned to the blood.
What are lymph capillaries?
name 4 characteristics they have.
Lymph capillaries end blindly and the lymph empties into the blood via the thoracic duct and right lymphatic duct. They have the following characteristics:
- Lymph capillaries consist only of a single layer of endothelium.
- The basal lamina is discontinuous or missing.
- No pericytes.
- Fibers of connective tissue anchor endothelium to surrounding tissue.
What are larger lymph vessels?
Name 3 characteristics
The larger lymph vessels have a structure similar to veins.
- Many valves
- Thinner walls than veins
- No red blood cells. Only lymphocytes.
To lymphatic system is lined up as a parallel system or as a system in series?
Parallel
What are the three differences between the circulatory system and the lymphoid system
Blood versus length
Heart pump versus no pump
Circulates versus unidirectional
