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MCAT Biology > C7 - Cardiovascular System > Flashcards

C7 - Cardiovascular System Flashcards

1
Q

What is the point of pulmonary circulation vs systemic circulation

A

The first pump is pulmonary circulation where deoxygenated blood returns from the body and moves into the lungs by way of the pulmonary arteries

2nd pump is systemic circulation where the left side of the heart receives oxygenated blood from the lungs by way of pulmonary veins and is then forced out to the body through the aorta

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2
Q

What has thicker and stronger walls of the atria vs ventricles. Why is this?

A

Atria a the thin wall structure. The ventricles are far more muscular than the atria allowing for powerful contractions necessary to push blood throughout the body

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3
Q

The atria and ventricles are seperated by what? While the ventricles are seperated from the vasculature by what?

A

Atria and ventricles are separated by the AV valves (atrioventricular valves)

Ventricles and vasculature is separated by the semilunar valves

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4
Q

What do the valves in the heart allow for?

A

The heart muscle to creat pressure within the ventricles necessary to propel blood forward within circulation, also preventing backflow of blood

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5
Q

What does the mnemonic LAB RAT stand for? And what valves are the semilunar valves? Where are all of these valves?

A

LAB RAT stands for: Left Atrium = Bicuspid; Right Atrium = Tricuspid
(These are the atrioventricular valves)

The semilunar valves:
Pulmonary valve is between the right ventricle and the pulmonary circulation

Aortic valve is between left ventricle and the aorta

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6
Q

What side of the heart is more muscular than the other side? Why is this?

A

The left side of the heart is more muscular than the right, this is because this side pumps the blood out of the heart it helps rest of the body.

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7
Q

In order of circulation what are the 4 electrically excitable structures in the heart?

A

Sinoatrial node (SA), atrioventricular node (AV), bundle of His and its branches, and the Purkinje fibers

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8
Q

Where is the SA node located?

A

In the wall of the right atrium

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9
Q

As the depolarization wave spreads from the SA node, what happens to the atria?

A

They contract simultaneously

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10
Q

While most ventricular filling is a passive process (blood moves into ventricles based on ventricular relaxation) what happens during atrial systole?

A

Atrial systole results in an increase of atrial pressure forcing a little more blood into the ventricles, this additional blood volume is called the atrial kick and accounts for about 5-30 percent of the CO

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11
Q

Where is the AV node located? What is special about this signal?

A

Located at the junction of the atria and ventricles, this signal is delayed to allow the ventricles to fill completely before they contract

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12
Q

Where is the bundle of His and its branches located?

A

It’s embedded in the interventricular septum (wall)

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13
Q

What do the purkinje fibers do?

A

They distribute electrical signals throughout the ventricular muscle

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14
Q

The muscle cells in the heart are connected by what structure? What does this allow for?

A

Connected by intercalated discs, which contain gap junctions directly connecting the cytoplasm of adjacent cells, this allows for coordinated ventricular contraction

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15
Q

Cardiac muscle has myogenic activity, what does this mean?

A

That the SA node generates about 60-100 bets per minute even if all innervation to the heart is cut. Neurological input is important in speeding up and slowing the rate of contraction, but not generating it in the first place

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16
Q

When does each main segement in an EKG occur?

A

P-wave occurs immediately before the atria contract

QRS complex occurs just before the ventricles contract

T-wave represents ventricular repolarization

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17
Q

What nerve is responsible for the parasympathetic signals that slow the heart rate down

A

Cranial nerve 10, the Vagus nerve

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18
Q

What happens in systole and diastole?

A

Systole: ventricles contract, and closure of the AV claves occur with blood being pumped out of the ventricles

Diastole: ventricles relax, semilunar valves are closed, and blood from the atria fills the ventricles

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19
Q

What is the cardiac output equation?

A

CO = HR x SV

CARDIAC OUTPUT = HEART RATE x STROKE VOLUME

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20
Q

What is the average CO in humans?

A

5 liters per minute

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21
Q

In a stethoscope when you hear S1,S2,S3,S4 what does it mean?

A

S1, the first sound. Is produced when the two AV valves close at the start of systole

S2, the second sound. Is produce when the two semilunar valves close at the end of systole

S3, and S4 are extra heart sounds, can result from stiffness of the heart muscle or high BP. These sounds are abnormal.

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22
Q

What branches off the aorta? Why do they branch off?

A

Major arteries, like common carotids, subclavians, and renal arteries. This allows the aorta to distribute blood throughout the body. These arteries listed are further and further divided.

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23
Q

Upon reaching the target, what does arteries branch into? What structure perfuses the tissues?

A

Arteries branch into arterioles which ultimately lead to capillaries that perfuse the tissues

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24
Q

What sends blood to perfuse the heart musculature?

A

The coronary arteries (located at the base of the aorta)

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25
Q

What are all blood vessels lined with? Name all the things it can do

A

Endothelial cells

-it helps to maintain the vessel by releasing chemicals that aid in vasodilation and vasoconstriction

-also allows WBC’s to pass through the vessel wall and into the tissues during an inflammatory response

-finally, they can release certain chemicals when damaged that are involved in the formation of blood clots to repair the vessel and stop bleeding

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26
Q

What has more smooth muscles, veins or arteries?

A

Arteries

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27
Q

A person suffering a heart attack is often given a Beta-blocker. What does this do?

A

It blocks sympathetic stimulation of the heart, resulting in a lower HR and contractility. Heart does not work as hard, so its oxygen demand is diminished

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28
Q

What are the only arteries that contain deoxygenated blood?

A

Pulmonary, and umbilical arteries

(This also means that the pulmonary, and umbilical veins are the only veins to carry oxygenated blood)

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29
Q

Arteries are highly muscular, and elastic. How does this affect blood flow?

A

It creates tremendous resistance to the flow of the blood.

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30
Q

How does the circulatory system overcome the resistance caused by systemic arteries?

A

After arteries are filled with blood. The elastic recoil from their walls maintains a high pressure and forces blood forward

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31
Q

Capallaries are a vessel with a single layer of what?

A

Endothelial cell layer

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32
Q

Capillaries are so small that red blood cells must pass through the capillaries in what way?

A

A single file line

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33
Q

What does the thin wall of the capillaries allow for?

A

The easy diffusion of gases, nutrients, and wastes.

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34
Q

Veins have less smooth muscle. What does this mean in terms of recoil? But they are able to stretch to accommodate larger quantities of blood, what does this mean in terms of how much blood they have in circulation?

A

The less amount of smooth muscle gives them less recoil than arteries. But 3/4 of our total blood volume may be in venous circulation at any one time.

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35
Q

Most blood flow in veins is upward from the lower body back to the heart, against gravity. What does this mean in terms of the pressure at the bottom of the venous column in the large veins of the legs?

A

It can be really high, in fact, it can exceed systolic pressure

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36
Q

What structures do large veins have to prevent back flow of blood and induce forward movement?

A

Valves

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37
Q

Failure of the venous valves results in what? Who is most susceptible to this result?

A

Varicose veins (causes blood to pool), most common in pregnant people due to increase of total blood volume, and compression of the inferior vena cava by the fetus

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38
Q

Veins also must rely on an external force to generate the pressure to push blood toward the heart, what would this be?

A

Skeletal muscle, most veins are surrounded by such muscles, which squeeze the veins as the muscles contract, forcing the blood up against gravity

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39
Q

Blood pools in the lower extremities, and what happens in sluggish blood more easily?

A

Coagulation

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40
Q

A clot in the deep veins of the leg is called what?

A

DVT - Deep vein thrombosis

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41
Q

This DVT clot can become dislodged and travel where, where it would be life threatening?

A

It could travel through the right side of the heart to the lungs, this is a condition called a pulmonary embolus

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42
Q

Patients with DVT, receive what medication usually?

A

Medications to prevent formation of clots like heparin, or warfarin

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43
Q

What structure returns blood to the heart?

A

The superior vena cava (SVC), and the Inferior vena cava (IVC)

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44
Q

Starting at the right atrium what is the complete circulation of blood including valves?

A

Right atrium > tricuspid valve > right ventricle > pulmonary valve > pulmonary artery > lungs > pulmonary veins > left atrium > mitral valve > left ventricle > aortic valve > aorta > arteries > arterioles > capillaries > venules > veins > inferior/superior vena cava > back to the right atrium

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45
Q

In most cases, blood will pass through only one capillary bed before returning to the heart. However, there are three portal systems in the body, in which blood will pass through two capillary beds in series before returning to the heart. Name them, and describe them.

A

-Hepatic portal system- blood leaving capillary beds in the walls of the gut passes through the hepatic portal vein before reaching the capillary beds in the liver

-Hypophyseal portal system- blood leaving capillary beds in the hypothalamus travels to a capillary bed in the anterior pituitary to allow for paracrine secretion of releasing hormones

-Renal portal system- blood leaving the glomerulus travels through an efferent arteriole before surrounding the nephron in a capillary network called the vasa recta

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46
Q

By volume how much of blood is liquid, and cells?

A

55% liquid

45% cells

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47
Q

What is the liquid portion of the blood called? What can it further be refined to?

A

It’s called plasma, contains nutrients, salts, respiratory gases, hormones, blood proteins. It can be further refined via the removal of clotting factors into serum

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48
Q

Cellular component of blood consists of what 3 major categories?

A

Erythrocytes, leukocytes, and platelets

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49
Q

All blood cells are formed from what stem cells? Where do they originate?

A

From hematopoietic stem cells, originating from bone marrow

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50
Q

Erythrocytes are specialized cells designed for what?

A

Oxygen transportation

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51
Q

How does each oxygen molecule get attached to the red blood cell?

A

It does NOT simply diffuse into the cytoplasm, rather it is attached to a hemoglobin molecule, which can hold 4 oxygen molecules per hemoglobin

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52
Q

Red blood cells have what shape? What purpose does this give it?

A

It has a biconcave shape

-helps assist them in traveling through tiny capillaries

-increases cells surface area, which increases gas exchange

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53
Q

What happens to RBC’s when they mature?

A

The nuclei, mitochondria, and other membrane bound organelles are lost. This makes space for hemoglobin molecules

54
Q

How do RBC’s generate ATP?

A

They do not carry out oxidative phosphorylation to generate ATP, rather, they rely entirely on glycolysis for ATP, with lactic acid as the main byproduct

55
Q

How long do RBC’s live? What happens to them when they get old?

A

They live 120 days in the bloodstream before cells in the liver and spleen phagocytize old red blood cells to recycle them for their parts

56
Q

What is hematocrit? And what is a normal measurement in males and females? And what is a normal hemoglobin for males and females?

A

It is a measure of how much of the blood sample consists of red blood cells, given as a percentage

Hematocrit normal range for males - 41-53%

Hematocrit normal range for females - 36-46%

-Hemoglobin-
-normal for males is between 13.5-17.5 g/dL

-normal for females is between 12.0-16.0 g/dL

57
Q

How much do leukocytes comprise of blood volume? When does this number change?

A

Usually Less than 1 percent. It changes when more is needed, like during an infected state

58
Q

What are the 2 main classes of granulocytes? What 5 basic types of leukocytes are under the 2 main classes?

A

Granulocytes (neutrophils, eosinophils, and basophils)

Agranulocytes (lymphocytes, and monocytes)

59
Q

Why are granular leukocytes or granulocytes named so? What is their function?

A

Because they contain cytoplasmic granules that have a variety of compounds that are toxic to invading microbes, these compounds are released through exocytosis

-involved in inflammatory reactions, allergies, pus formation, and destruction of bacteria and parasites

60
Q

What process are lymphocytes important in? What are some ways these cells can act?

A

The specific immune response, the body’s fight against particular pathogens, such as viruses and bacteria

-they can act as primary responders against an infection, while others function to maintain a long term memory of pathogen recognition

61
Q

Many vaccines train what cells?

A

Lymphocytes

62
Q

What are the 2 main types of lymphocytes? Where do they come from and what do they do?

A

Lymphocytes that mature in the bone marrow are referred to as B-cells. They are responsible for antibody generation

Lymphocytes that mature in the thymus are called T-cells. These cells are responsible for killing virally infected cells and activate other immune cells

63
Q

What do monocytes do?

A

Phagocytize foreign matter such as bacteria

64
Q

Once monocytes leave the bloodstream and enter an organ they are renamed to what? They also have specific names depending on what organ they are in. What are they called in the nervous system, the skin, and bone for example?

A

Overall they are renamed macrophages. In the nervous system they are called microglia, in the skin it’s langerhans cells, and in the bone they are osteoclasts

65
Q

Thrombocytes or platelets are cell fragments or shard released from cells in bone marrow called what?

A

Megakaryocytes

66
Q

What are platelets function?

A

Assisting in Blood clotting

67
Q

Production of blood cells and platelets is called what?

A

Hematopoiesis

68
Q

Hematopoiesis is triggered by a number of hormones, growth factors, and cytokines. What is the most notable? Where does it come from, and how does it work?

A

Erythropoietin, which is secreted by the kidney and stimulates mainly red blood cell development, and thrombopoietin, which is secreted by the liver and kidney and stimulates mainly platelet production

69
Q

What are the 2 main surface proteins in RBC’s?

A

Antigens, and Rh factors

70
Q

What is an antigen?

A

Any specific target (usually a protein) to which the immune system can react

71
Q

What are the 2 major antigen families relevant for blood groups?

A

ABO antigens

Rh factor

72
Q

In the ABO system, what alleles are codominant, what is recessive?

A

O is recessive. A and B alleles are codominant

73
Q

What are the 4 blood types

A

A,B,AB,O

74
Q

What are the genotypes for blood type A, and B,

A

Genotype for A: IA IA, IA i

Genotype for B: IB IB, IB i

75
Q

Type O blood cells express neither antigen variant, what does this mean? How is this different from A and B?

A

They will not initiate any immune response, regardless of the recipients actual blood type.

In A blood it will recognize the A protein as self, and B as foreign and will make antibodies to types AB, and B. Same for B making antibodies for A

76
Q

What is the universal donor and universal recipient blood type? Why is this?

A

Universal donor is blood type O. This is because their blood will not cause ABO-related hemolysis in any recipient

Universal recipient is blood type AB. This is because no blood antigen is foreign to individuals who have AB blood, so no adverse reactions will occur upon transfusion.

77
Q

What blood type do people with O need? And why?

A

They can only receive blood type O. This is because they produce anti-A and anti-B antibodies

78
Q

Whole blood is never given in transfusions, rather what happens?

A

Packaged red blood cells with no plasma are generally given.

79
Q

When are antibodies made?

A

Only in response to an antigen, and they specifically target that antigen

80
Q

Why, then, does an individual lacking the A allele automatically have an anti-A antibody?

A

E. Coli that inhabits the colon may have proteins that match the A and B alleles. This would serve as a source of exposure and would allow one to develop anti-A/B antibodies prior to exposure to another person blood.

81
Q

What are the most common and least common blood types in the US?

A

Most common: O+

Least common: AB-

82
Q

What are the 2 main Rh variants? What do these 2 variants refer to?

A

Negative and positive, referring to whether they have the presence or absence of a specific allele called D.

Those absent are thus -, present are +

83
Q

Rh-positivity follows what pattern in inheritance?

A

Autosomal dominant inheritance, thus one positive allele is enough for the protein to be expressed

84
Q

Describe the condition of erythroblastosis fetalis. What causes it?

A

It happens when a person who is pregnant is Rh- (or positive, it just needs to be opposite of the fetus) and the fetus is Rh+, the person will become sensitized to the Rh factor upon blood contact and the persons immune system will begin to make antibodies. Notice it is not USUALLY a Problem for the first child as by the time the antibodies are produced, the child is already born. Therefore a subsequent pregnancy in which the fetus is Rh+ will result in a problem as maternal anti-Rh antibodies are then present and can cross the placenta and attack the fetal blood cells, resulting in hemolysis of the fetal cells.

85
Q

Why is there less concern with maternal-fetal ABO mismatching?

A

Because antibodies against AB antigens are of a class of IgM, which do not readily cross the placenta (unlike anti-Rh IgG antibodies, which can)

86
Q

What is BP a Measurement of? What measures BP

A

The force per unit area exerted on the wall of the blood vessels; measured by a sphygmomanometer (it measures the gauge pressure in systemic circulation, which is the pressure above and beyond atmospheric pressure

87
Q

Pressure gradually drops from the arterial to venous circulation. When is the biggest drop?

A

Biggest drop occurs across the arterioles.

This is because capillaries are unable to withstand the pressure of the arterial side of the vasculature

88
Q

The equation for pressure differential across circulation?

A

Delta P = CO X TPR

CO- cardiac output

TPR- total peripheral resistance

89
Q

What are the 3 factors resistance is based on? What 2 play a huge factor in human physiology, especially in BP?

A

Resistance is based on resistivity, length, and cross-sectional area; length and cross-sectional area being the most relevant for the MCAT and physiology

Longer a blood vessel is the more resistance it offers

The larger the cross-sectional area of a blood vessel, the less resistance it offers

90
Q

What do Baroreceptors do? What are they?

A

They are specialized neurons, that detect changes in the mechanical forces on the wall of the vessel (changes in pressure). When BP is sensed to be too low it can trigger vasoconstriction, along with many other things

91
Q

What big role do chemoreceptors play in BP regulation?

A

They can sense when the osmolarity of the blood is too high, which could indicate dehydration, promoting release of ADH

92
Q

Low perfusion to the juxtaglomerular cells of the kidney would also stimulate what in relation to BP?

A

Aldosterone, released through the renin-angiotensin-aldosterone system

93
Q

What is ANP? Where does it come from and what does it do? How rampant are these effects?

A

Atrial natriuretic peptide is a hormone that is secreted by specialized atrial cells. It aids in the loss of salt from within the nephron, acting as a natural diuretic with loss of fluid.

However it is a fairly WEAK diuretic and often not enough to counter the effects of high BP

94
Q

What gas and solute exchange occurs when blood reaches the capillaries? What overlapping concept is KEY to remember about this process?

A

Oxygen, nutrients diffuse out of the blood into tissues. Waste products like CO2, H+, urea, and ammonia diffuse into the blood. Also hormones are secreted into the capillaries and travel through circulation to their target tissues

Key thing to remember is that it is all controlled by a CONCENTRATION GRADIENT. One side of the capillary wall has a higher concentration of a given substance than the other allowing for the movement of gases and solutes by diffusion

95
Q

Oxygen is primarily carried by what molecule? Where is it binded to?

A

Hemoglobin, it is made up of four cooperative subunits each of which has a prostetic heme group that binds to an oxygen molecule.

Oxygen is binded to the heme groups central iron atom

96
Q

What type of reaction is the binding or releasing of oxygen to or from the iron atom in the heme group?

A

A oxidation-reduction reaction

97
Q

Does oxygen diffuse into the blood and dissolve in the plasma?

A

Yes but this amount is negligible compared to how much binds to hemoglobin

98
Q

The level of oxygen in the blood is often measured as what? But how is it viewed clinically?

A

Partial pressure of O2, normal being 70-100 mmHg. But clinically it is observed through oxygen saturation, that is the percentage of hemoglobin molecules carrying oxygen and is measured by a finger probe. Healthy O2 saturation is above 97%

99
Q

Describe the binding of oxygen to the heme group and its affinity along with its detachment.

A

As the first oxygen binds to a heme group, it induced a conformational shift in the shape of hemoglobin. This increases hemoglobins affinity for oxygen. This makes it easier for subsequent molecules of oxygen to be added, as the other heme groups acquire an oxygen the affinity continues to increase

Once they are all bound, the removal of one molecule of oxygen will induce a conformation change, decreasing the overall affinity for oxygen, making it easier for the other molecules of oxygen to leave the heme groups. Again but conversely, it progressively gets easier until they are all gone.

Both are a positive feedback process.

This is a form of allosteric regulation referred to as cooperative binding and results in the classic sigmoidal (S-shaped) oxyhemoglobin dissociation curve

100
Q

What is the primary waste product of cellular respiration?

A

CO2

101
Q

Both O2, and CO2 gas have what polarity

A

Nonpolar, therefore they have low solubility in an aqueous solution such as plasma which is relevant to blood

102
Q

Can CO2 be carried by hemoglobin?

A

Yes, but it had a much lower affinity for it than oxygen

103
Q

The vast majority of CO2 exists as what in the blood?

A

Bicarbonate ions (HCO3-)

104
Q

Upon entering the blood, how is CO2 converted into carbonic acid?

A

It encounters an enzyme called carbonic anhydrase, which catalyzes the combination reaction between carbon dioxide and water to form carbonic acid (H2CO3)

105
Q

What type of acid is carbonic acid and what happens when in solution?

A

It is a weak acid that dissociates into a proton and bicarbonate anion (H+ and HCO3-)

this makes them easier to transport

106
Q

When reaching the lungs from the alveolar capillaries what happens to the bicarbonate anion and proton?

A

It is reversed back to CO2 where it can be expelled

107
Q

Including the enzyme, what is the bicarbonate buffer equation? Include phases

A

CO2(g) + H2O(l) <> carbonic anhydrase <> H2CO3(aq) <> H+(aq) + HCO3-(aq)

108
Q

When does the Bohr effect?

A

When there is an increase in CO2 production it causes a right shift in the bicarbonate buffer equation, resulting in increased H+ and decrease in pH. These protons can bind to hemoglobin, reducing hemoglobins affinity for oxygen

109
Q

In the oxyhemoglobin curve what does the right shift and left shift mean?

A

Left shift means there is a higher affinity for oxygen molecules for the hemoglobin

Right shift means there is a less affinity for oxygen molecules for the hemoglobin

110
Q

What are the causes of a oxyhemoglobin right shift curve?

A

-increase temperature

-increase 2,3 biphosphoglycerate (2,3-BPG) a side product of glycolysis in red blood cells

-increase partial pressure of CO2

-increase H+, decrease pH

111
Q

Difference between fetal and adult hemoglobin?

A

Fetal hemoglobin has a higher affinity for oxygen than adult hemoglobin, this is because fetal RBC’s must literally pull oxygen off of maternal hemoglobin and into fetal hemoglobin

112
Q

What happens in the bicarbonate buffer system if someone hyperventilates? What condition can be caused?

A

This expells excess CO2 and shifts the equation to the left. This decreases the concentration of protons, thus increasing pH

This is known as respiratory alkalosis

113
Q

In absorption of carbohydrates and amino acids in the small intestine, how does it enter systemic circulation?

A

Via the hepatic portal system

114
Q

Where are fats absorbed in the small intestine? And how does it get to systemic circulation?

A

It is absorbed into the lacteals in the small intestine, bypassing the hepatic portal circulation to enter systemic circulation via the thoracic duct

115
Q

When lipids are released from intestinal cells what happens to them?

A

They are packaged into lipoproteins (water soluble)

116
Q

In blood stream what are the 2 opposing forces that maintain proper fluid volume?

A

Hydrostatic and osmotic (oncotic) pressure

117
Q

What is hydrostatic pressure? How is it generated? What does it do in the bloodstream?

A

It is the force per unit area that blood exerts against the vessel walls. It is generated by the contraction of the heart and the elasticity of the arteries.

It pushes fluid out of the bloodstream and into the interstitium (the cells surrounding the blood vessels) through the capillary walls

118
Q

What is osmotic pressure generated by? What else is it called? And what does it do?

A

Osmotic pressure, is the “sucking” pressure generated by solutes as they attempt to draw water into the bloodstream.

It is mostly attributed to plasma proteins, so it is also usually called oncotic pressure

119
Q

How does the hydrostatic pressure and oncotic pressure change from the arteriole end to the venule end?

A

At the arteriole end, hydrostatic pressure is much larger than oncotic pressure, here there is a net efflux of water from circulation. As fluid moves out of the vessels, hydrostatic pressure drops while oncotic stays relatively the same. Therefore at the end of the venule end, hydrostatic pressure is below oncotic pressure, hence there is a net influx of water back into circulation

120
Q

What is the balance of opposing pressures called?

A

Starling forces

121
Q

Accumulation of excess fluid in the interstitium results in what condition?

A

Edema.

122
Q

Some interstitial fluid is also taken up by what system? How is it then returned back to the central circulatory system?

A

It is taken up by the lymphatic system. Then most lymphatic fluid (lymph) is returned back to the central circulatory system by way of a channel called the thoracic duct

123
Q

Osmotic pressure is dependent on what?

A

The number of particles dissolved in the plasma

124
Q

What are clots composed of?

A

Platelets and coagulation factors (proteins)

125
Q

When the endothelium of a blood vessel is damaged how does it trigger the complex cascade effect?

A

When damaged, it is exposed to underlying connective tissue, which contains collagen and a protein called tissue factor. When platelets contact with exposed collagen, they sense injury and in response release their contents and begin to aggregate, or clump together. Simultaneously, coagulation factors sense tissue factor and initiate a complex activation cascade

126
Q

Most coagulation favors are scecreted from where?

A

The liver

127
Q

What is the endpoint of the cascade? And how does it get to the point of a clot?

A

The endpoint is the activation of prothrombin to form thrombin by thromboplastin. Thrombin then converts fibrinogen to fibrin. Ultimately fibrin forms the smaller fibers that aggregate and cross link into a woven structure, like a net that captures red blood cells and other platelets, forming a stable clot over the area of damage

128
Q

A clot that forms on a surface vessel that has been cut is called a…

A

Scab

129
Q

How does blood clotting begin? (How does it add onto the begging clot)

A

Platelets attach to the matrix that becomes exposed when the endothelial cells lining blood vessels are disrupted. This attachment activates quiescent integrin molecules, causing them to adhere to circulating proteins including fibrinogen, which forms bridges to additional platelets

Together the cells proteins ultimately provide a network of cells and fibers dense enough to plug injury and prevent blood loss until the wound is repaired

130
Q

Ultimately the clot will have to be broken down. How so this accomplished?

A

It’s accomplished predominantly by plasmin, which is generated from plasminogen

131
Q

What trouble does hemophilia cause in humans?

A

This genetic disease causes distinctions in the cascade of clotting reactions and increases the risk of life threatening blood loss even from relatively more injuries.

Most common is hemophilia A

MCAT Biology (12 decks)

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