Cardiovascular System

Micro Exam 2

What are the layers of the heart from deep to superficial?

Endocardium - myocardium - epicardium - fibrous skeleton

What lies on top of the epicardium?

Visceral pericardium

What is between the visceral and parietal pericardium?

pericardial fluid

What are the two layers of tissue making up the endocardium?

endothelium and subendothelium

What makes up the endothelium?

simple squamous epithelium + basal lamina

What makes up the subendothelium?

Loose CT, scattered smooth muscle fibers, and cells of impulse conducting system (purkinje fibers)

What is the endothelium continuous with?

vascular and lymph systems

What are the functions of the endothelium?

antithrombogenic barrier and release growth factors

T/F: Large blood vessels run through the subendothelium

False; small blood vessels run through

The myocardium is thickest in which chamber of the heart?

left ventricle

What does the epicardium contain?

Loose CT, scattered adipocytes, blood vessels (coronary arteries), autonomic nerve fibers, and mesothelium

What is the mesothelium?

The single, squamous epithelial layer that is the outermost layer of the epicardium

Describe the pericardium:

Continuous double layer of simple, squamous epithelium that surrounds the heart

What is the purpose of pericardial fluid?

lubrication and protection

__% of CO goes immediately into the coronary arteries

5

What is the cardiac skeleton made up of?

Dense irregular connective tissue; annuli fibrosis surrounds and anchors valves; fibrocartilage

What is the function of the cardiac skeleton?

Muscle attachment at intraventricular septum and intra-atrial septum; electrical insulation

What are the cardiac valves composed of?

Dense connective tissue continuous with cardiac skeleton and covered with endothelium

Why do we have endothelium surrounding the valves in our heart?

to prevent blood clots

The mitral and tricuspid valves close during ____________

systole

The aortic and pulmonic valves close during ____________

diastole

What does the SA node stimulate?

atrial contraction

What does the AV node do?

Delays signal to ventricles

What does the purkinje system do?

Impulse conduction throughout both ventricles

The impulse conduction system consists of what type of muscle fibers?

modified cardiac

What innervation influences the SA and AV nodes?

autonomic nervous system

What is similar between cardiac myocytes and skeletal myocytes?

Similar myofibrils and connective tissue wrappers

Cardiac myocytes are ___________ meaning the have multi-directional force production

bifurcate

Mitochondria make up ___-___% of cardiac myocytes vs ___-___% in skeletal myocytes

30; 40; 2; 20

What is the primary fuel for cardiac myocytes?

Fatty acids/triglycerides; glycogen too

Cardiac muscle innervation can be described as:

Intrinsic and spontaneous contraction

T/F: there are no neuromuscular junctions or motor end plates involved in cardiac muscle innervation

True

Intercellular communication in cardiac muscle is through what?

Electrical synapse via gap junctions

T/F: Cardiac muscle needs external input to contract

False; it does NOT

Cardiac muscle cells contain:

gap junctions, desmosomes and fascia adherens (cadherins)

Gap junctions in cardiac muscle cells allow for...

rapid impulse conduction

Gap junctions are like a hand __________ passed down a line and signal propagation via ion channels is like a hand ________

squeeze; shake

Electrical signal transmission via ion channels requires every ___ and ___ channel to open and close to pass the signal

Na+; K+

What percent of blood is typically hanging out in our veins?

75%

Describe the tunica intima:

Inner lining of vessel, endothelium, basal lamina & connective tissue; subendothelium made up of loose CT; internal elastic lamina in some vessels

Describe the tunica media:

Middle layer, highly variable composition and thickness, contains smooth muscle with gap junctions and/or elastic lamellae (sheets); CT includes reticular, elastic, and small collagen fibers; ground substance and external elastic lamina in some vessels

Describe the tunica adventitia:

Outer covering, loose CT, fibers primarily collagen type I and elastic, ANS nerve endings, they have their own blood vessels (vaso vasorum) in larger vessels

Where is the endothelium?

endocardium, all blood and lymphatic vessels

Capillaries are made up of ________________ only

endothelium

What is the function of the endothelium in the capillaries?

control, facilitate and monitor metabolic exchange

What is secreted by endothelium creating a non-thrombogenic surface?

Heparin (anticoagulant), tissue plasminogen activator (dissolves blood clots) and von Willebrand factor (dissolves blood clots)

If platelets contact the subendothelial tissue what will happen?

Clots will form because the blood is no longer hitting a non-thrombogenic surface

The endothelium produces/secretes substances that regulate/modulate:

vascular permeability, inflammatory responses and vessel remodeling

What does vascular tone consist of?

Vasoconstriction vs vasodilation

An increase in tone = increase in _____________

contraction

What are the intrinsic molecules resulting in increased BP with increased vascular tone?

Endothelin-1 and the Renin-Angiotensin System

Briefly describe the Renin-angiotensin system:

1) Renin from the kidneys converts angiotensinogen into angiotensin I; 2) angiotensin-converting enzyme converts angiotensin I to angiotensin II; 3) angiotensin II causes an increase in blood pressure

What are some extrinsic medications that are vasopressors?

Alpha-adrenergic agonists (used in ICU, trauma, shock); Nasal decongestants (topical or nose bleeds)

What do ACE inhibitors do to decrease BP?

Stop angiotensin I from becoming angiotensin II

What intrinsic molecules decrease our vascular tone?

Nitric oxide, histamine and muscle work

What extrinsic medications decrease decrease our vascular tone?

Nitroglycerin (sublingual), ACE inhibitors, angiotensin II receptor blockers

The names of ACE inhibitors end in what suffix?

-pril

The names of angiotensin II receptor blockers end in what suffix?

-sartan

When endothelial cells are damaged there is expression / increased expression of:

1) Pro-thrombotic factors; 2) Vasoconstriction factors; 3) Pro-inflammatory factors; 4) Growth factors

Long term damage of endothelial cells results in what?

atherosclerosis

What are some examples of elastic (conducting) arteries?

Aorta, common carotid, subclavian, and common iliac

What are some examples of muscular (distributing) arteries?

Most named arteries aside from the elastic arteries

What is the diameter of small arteries and arterioles?

0.1-1 mm diameter; 10-100 micrometer diameter

T/F: Some arteries don't have tunica intima

False; all arteries have tunic intima

Describe the structure of elastic arteries:

40-70 layers of fenestrated elastic sheets

Describe the functions of elastic arteries:

Accomodate large volume changes, smooths blood flow, and acts as a PASSIVE auxilary pump

Describe the structure of muscular arteries:

Up to 40 layers of smooth muscle with inner/outer elastic lamina

Describe the functions of muscular arteries:

Aids in regulation/distribution to organs and body regions, respond to functional demands, and have a role in maintaining BP

How many layers of smooth muscle make up small arteries? Arterioles?

3-10; 1-3

What are the functions of small arteries and arterioles?

Regulate distribution to capillary beds and regulate blood pressure

Describe the tunica adventitia in arteries:

Dense irregular and loose CT; Elastic and muscular arteries have vaso vasorum, lymphatic vessels and nerve fibers; Small arteries and arterioles have a thin layer of CT and some nerve endings

Describe the arteriovenous shunt:

Bypass vessel between arterioles and venules

What is the portal system? What is its purpose?

Microvascular pathway made up of capillary beds in series; Moves high concentration of molecules to the next bed over; Present in GI to liver, kidneys and hypophyseal portal system

Describe the structure of capillaries:

Endothelium and basal lamina; intercellular junctions and variable leakiness; generally 4-10 micrometers in diameter; grouped into beds

Describe the function of capillaries:

1) Selective barrier; 2) exchange of gas, nutrients, and wastes

Describe continuous capillaries:

Most selective, continuous basal lamina and cell layer with tight junctions; O2/CO2 freely diffuses but vesicle transport is required for all other molecules

Where are continuous capillaries located?

Muscle, CT, exocrine glands, nervous tissue, blood brain barrier

Describe fenestrated capillaries:

Moderately leaky capillaries with continuous basal lamina but fenestrated endothelial cells; change is more extensive and rapid than in continuous capillaries

Where are fenestrated capillaries located?

Kidney, digestive tract, and endocrine glands

Describe discontinuous capillaries:

Discontinuous basal lamina, fenestrated epithelial cells, cells can move across capillary, and extensive change between blood and extravascular space

Where are discontinuous capillaries found?

Liver, bone marrow, spleen, and some endocrine glands

Describe metarterioles:

short vessels that link arterioles and capillaries; precapillary sphincters made up of bands of smooth muscle; open = flow into capillaries; closed = flow directly into postcapillary venules

Compared to arteries veins have:

Larger lumen, thinner walls, lower pressures, higher concentration of CT, less smooth muscle and tunica adventitia is the thickest layer

Describe the tunica intima in venules:

Endothelium with basal lamina, NO subendothelium and responds to histamine

Describe the tunica media in venules:

incomplete layer of smooth muscle

Describe the tunica adventitia in venules:

thin layer of CT

Describe the tunica intima in small, medium and large veins:

endothelium with basal lamina

Describe the tunica media in small and medium veins:

bundles of smooth muscle; 2-5 layers

Describe the tunica adventitia in small and medium veins:

thick layer of CT

What size veins are the cutaneous and deep veins of the extremities?

Small-medium

Describe the tunica media in large veins:

Smooth muscle; >5 layers

Describe the tunica adventitia in large veins:

Thick layer CT, smooth muscle, cardiac cells near heart

What are some examples of large veins?

IVC, splenic, superior mesenteric and external iliac

What assists / directs blood flow through the veins?

Valves

Describe the structure of valves in veins:

Endothelium covering and thin layer of CT; most numerous in medium-large veins of LE and lower trunk

Describe lymphatic fluid:

Interstitial fluid of large molecules and lipids

Lymphatic capillaries are _____ permeable than most blood capillaries

more

What do lymph nodes do?

Filter lymph and immune response

Describe the structure of the lymphatic system:

Lymph capillaries - precollectors - collectors - trunks - ducts - subclavian arteries

The diameter of lymphatic capillaries is __________ than blood capillaries

greater