Unit 2 - Circulation

Erythrocyte

RBC

Leukocyte

WBC

Thrombocyte

Platelet

What forms plasma?

serum + clotting proteins, albumin, globulins + lipids and carbs

Oedema

general, excess interstitial fluid in tissue, less blood in capillary

Effusion

fluid buildup in a specific cavity/joint

Exudate

type of fluid buildup, high protein, high cells levels

Transudate

type of fluid buildup, low protein, few cells

Ascites

fluid buildup in the abdominal cavity

Hydropericardium

fluid buildup in the pericardium of the heart

Hydrothorax

buildup of transudate fluid in the pleural space (between lungs and chest wall)

Peripheral oedema

fluid buildup in the legs, ankles, feet, hands, arms (limbs)

Inflammatory oedema

oedema caused by the increased permeability of the endothelium

Noninflammatory oedema

an oedema caused by anything other than endothelium permeability

What are the mechanisms/causes of oedema?

• increased permeability (inflammation)

• increased venous hydrostatic pressure (heart failure, postural oedema)

• reduced colloidal osmotic pressure (hypoproteinaemia, kwashiorkor)

• lymphatic vessel obstruction (removal of lymph node)

• increased total body water (renal failure)

Hyperemia

excess of blood in vessels around the body, all capillary beds are open, an active process, vasodilation

Congestion

impaired outflow (venous drainage), blood accumulates in venules and capillaries, a passive process

Ischaemia

reduces flow of blood either on the arterial side or the venous side

Arterial Ischaemia

vasoconstriction of the arterioles (active), causes blood clots

Venous Ischaemia

vascular congestion (backflow)

Infarction

death of tissue due to ischaemia, occurring in end-artery systems

End-Artery System

arteries that have few/no significant connections to other vessels (brain, heart, kidney)

Venous Infarct

obstructed vein, tissue turns red

Arterial Infarct

thrombus (blood clot) blocks artery, tissue turns pale

Heart Attack

infarction of the heart

Stroke

infarction of the brain

What type of cell death does an arterial infarct cause?

coagulation necrosis (tissue has not changed, just colour)

Haemorrhage

blood outside the vascular system

External Haemorrhage

bleeding outside the body (skin, stomach, intestines)

Internal Haemorrhage

bleeding into internal cavitie/tissues (haemoperitoneum, haemopericardium)

Haematoma

large internal haemorrhage, forms swelling/mass/cavity

ex. blood blister, swelling from broken leg, etc.

Ecchymosis

medium sized internal haemorrhage

ex. black eye, severe hickey, some bruising, etc.

Petechia

small internal haemorrhage, aka pinpoint haemorrhage

ex. hickey, small bruising, etc.

Blood Clot

general term for a coagulation of blood

Postmortem Clot

blood clot after death, within a vessel

Thrombus

blood clot in the vessels of a living being

What is needed to maintain haemostasis?

• endothelial cells

• platelets

• coagulation proteins

How do endothelial cells aid in haemostasis?

they are normally anticoagulant (allows blood to flow), become procoagulant when injured (to allow blood to clot)

What causes a haemorrhage?

1+ of the haemostasis factors has been affected

Extrinsic Coagulation Pathway

1. tissue damage

2. release of factor III

3. factor VII activated

4. factor X activated

5. prothrombin → thrombin (active)

6. fibrinogen → fibrin (active)

7. blood clot forms

Intrinsic Coagulation Pathway

1. factor XII activated

2. factor XI activated

3. factor IX activated

4. factor VIII activates factor X

5. prothrombin → thrombin (active)

6. fibrinogen → fibrin (active)

What causes haemophilia?

a deficiency of coagulation factors VIII or IX

What are the steps in a blood clot?

1. endothelium breaks (collagen is exposed)

2. platelets are attracted to the collagen

3. when platelets bind to collagen, it releases cytokines

4. coagulation cascade occurs

5. fibrin and coagulation proteins form the clot

What are the ways to measure haemostasis?

• platelets

• intrinsic and common system

• extrinsic pathway

How do you measure platelets?

• bleeding time (pinprick, how long till it stops bleeding?)

• platelet count (blood sample → lab)

How do you measure the intrinsic and common pathway?

activated partial thromboplastin time (APTT), blood sample → lab, testing the time it takes from F12 → fibrin (clot)

How do you measure the extrinsic pathway?

prothrombin time (PT), measures the extrinsic pathway (F3 → fibrin/clot)

Pulmonary Thrombus

formation of blood clot in the lung, mostly in the pulmonary artery, common on planes (25% of passengers), severe ones can kill

Why do thrombi form?

• endothelial injury

• altered blood flow

• hypercoagulability

What are examples of how endothelial injury can cause thrombus formation?

• atherosclerosis

• severe trauma (can cause abnormal clotting)

• surgery

What are examples of how altered blood flow can cause thrombus formation?

• stagnation

• turbulence

• deep vein thrombosis

• travel related venous thromboembolism

Atherosclerosis

plaque buildup in arteries

Stagnation

no muscle movement for a long period of time, common in large arteries in legs

Turbulence

endothelial injury, activates platelets, common in aneurisms

Deep Vein Thrombosis

prolonged period of no movement, commonly in the deep veins of the legs

What are examples of how hypercoagulability can cause thrombosis?

• smoking

• obesity

• cancer

• chronic disease

Disseminated Intravascular Coagulation (DIC)

excessive thrombosis throughout a specific organ or throughout the body (thrombi in many capillaries), consumption of platelets and clotting factors → infarcts and haemorrhages

What are clinical signs of disseminated intravascular coagulation

• infarction

• petechiae

• excessive bleeding (prolonged bleeding time, PT and APTT)

• platelet deficiency

Embolism

unusual/foreign substance moving through the blood (thrombus or other)

Thrombotic Embolism

thrombus moving through the blood, stopping in a capillary

ex. pulmonary thromboembolism - PTE (embolism of the lung)

How can gas cause embolism?

rapid change in pressure can cause bubble to form in the body, tears to form in lungs/tissues, bubbles enter blood

ex. decompression sickness - DCS (cant fly on plane after scuba diving)

How can an injection cause embolism?

foreign substance enters bloodstream from a needle injection

ex. air bubble in IV catheter

How can marrow cause embolism?

fractures of the bone cause contents of bone to enter the bloodstream and go to the lungs

How can neoplastic cause embolism?

cancer cells shed into the bloodstream, leading to clots and blockages

Shock

widespread hypoperfusion of tissues → reduces cardiac output and/or reduced effective circulating blood volume

Hypoperfusion

less blood going to critical organs

What are some causes of shock?

• cardiogenic

• hypovolemic

• blood maldistribution

Cardiogenic Shock

heart failure (not beating properly) → reduces blood pressure

Hypovolemic Shock

less blood (haemorrhage) or plasma (dehydration)

Blood Maldistribution Shock

• neurogenic shock

• septic shock

• anaphylactic shock

Neurogenic Shock

nervous system cannot regulate vessels → widespread vasodilation, non-traumatic hypotension (brain doesn’t like situation), spinal cord trauma

Septic Shock

widespread infection causes extreme immune response → extreme hypotension

Anaphylactic Shock

allergic reaction → extreme immune response → airways narrow, blood pressure drops, etc.