Blood & CV systems Flashcards Preview

Anatomy and Physiology > Blood & CV systems > Flashcards

Flashcards in Blood & CV systems Deck (35):
1

Functions of blood

Transports oxygen, carbon dioxide, water, hormones, nutrients, waste products, heat
Protects - blood clotting, immunity, inflammation
Regulates body fluid, pH, hormones, temperature

2

Properties of blood

Viscosity (resistance to flow)
Osmololality (concentration)

3

How many litres of blood does an average adult have?

4-6L
Plasma (55%) - clear extracellular fluid
Cells (45%)
Centrifugation separates cells from plasma

4

What are the components of plasma?

Nutrients: glucose, gases, electrolytes, Na+ (90% of plasma electrolytes) hormones,
plasma proteins
Organic waste products:
Urea, creatinine, uric acid
toxic breakdown products removed by the kidneys

5

Name the 3 plasma proteins found in the blood

Albumin -
- most abundant plasma protein
produced by liver
- influences blood pressure, flow and fluid balance
Fibrinogen and clotting factors-
- produced by liver
- responsible for coagulation of the blood
Globulins -
- produced by plasma cells
- immunity

6

Erythrocytes (RBC)

Gas transport: O2 and CO2
Disc-shaped cell with thick rim =
increased surface area/volume ratio
No nucleus or organelles
Cannot multiply (120 days life span)
Contain:
- haemoglobin
- carbonic anhydrase enzyme
produces carbonic acid from CO2 and water

7

Haemoglobin structure

4 protein chains (globins)
Each chain contains haem which allows oxygen to bind
Each Hb molecule can carry 4 oxygen molecules
Foetal Hb has a higher affinity to oxygen than adult Hb

8

How do you measure erythrocyte concentration in clinical practice?

Haematocrit - packed cell volume (PCV)
Mean cell volume (MCV)
Erythrocyte count
Mean cell Hb (MCH)

9

Define erythropoiesis

Process of the development of red blood cells from stem cells
Immature cells released into bloodstream as reticulocytes, and mature into erythrocytes

10

What 2 things are required for blood cell synthesis?

Vitamin B12 and folic acid (have to be bound to intrinsic factor to allow absorption to take place

11

Which hormone regulates red blood cell production?

Erythropoietin, produced in the kidneys

12

What is haemolysis?

The breakdown of erythrocytes

13

Leukocytes (WBC)

Important function in defence and immunity
Contain nuclei
Granulocytes:
> neutrophils - increase in bacterial infections, phagocytosis
> eosinophils - increase in parasitic infections eg. worms
> basophils - closely associated with allergic reactions (contain histamine), chicken pox
Agranulocytes:
> lymphocytes - increase in chronic infections and immune response, destroy foreign/virally cells, found in lymph nodes and spleen
> monocytes - become tissue macrophages, produce interlukin-1

14

Platelets

Secrete:
- clotting factors
- factors for endothelial repair
- vasoconstrictors in broken vessels
Form temporary platelet plugs
Dissolve old blood clots
Attract WBCs to sites of inflammation to phagocytose bacteria

15

Define haemopoiesis

Production of blood cells

16

What tissues produce blood cells?

1.yolk sac (in embryo)
2. liver, spleen (until birth)
3. red bone marrow
produces RBCs, WBCs and platelets
4. lymphoid tissues
WBC production, maturation

17

Erythrocyte production

Erythropoiesis in red bone marrow produces 2.5 mil RBCs/second
Development takes 3-5 days
- reduction in cell size
- synthesis of Hb
- loss of nucleus

18

Recycling of erythrocytes

RBCs live for 120 days
- fragile membrane
- cell bursts in narrow channels in the spleen
Macrophages in spleen & liver
- digest cell components
- convert haem to bilirubin
- becomes bile product in faeces

19

Erythrocyte homeostasis

NEGATIVE FEEDBACK
- drop in RBC count = hypoxemia to kidneys
- EPO production increases
- stimulation of bone marrow
- RBC count increases in 3-4 days
Causes of hypoxia:
Lung disease
smoking
high altitude
increase in exercise
bleeding

20

What is anaemia?

Inability of the blood to carry enough oxygen to meet body needs
- low levels of haemoglobin
- faulty haemoglobin
- loss of blood
- inadequate nutrition

21

Terms used to describe RBC characteristics

Normochromic - cell colour normal
Normocytic - cells normal size
Microcytic - cells smaller than normal
Macrocytic - cells bigger than normal
Hypochromic - cells paler than normal
Haemolytic - rate of cell destruction raised
Megaloblastic - cells large and immature

22

Types of anaemia

Diet induced:
eg. iron deficiency
eg. Vitamin B12/folic acid deficiency - pernicious (autoimmune) and dietary deficiency
Macrocytic/microcytic
Haemolytic - RBCs are destroyed or removed prematurely
Aplastic - bone marrow failure

23

Haemostasis

Primary haemostasis = temporary platelet plug
Secondary haemostasis = coagulation, stable clot

24

Vascular spasm

Prompt constriction of broken vessel
Triggered by:
> pain receptors (few mins)
> injury to smooth muscle (longer-lasting constriction)
> platelets release chemicals = serotonin
- provides time for other 2 mechanisms to work

25

Platelet plug formation

Injury = primary haemostasis
- vasoconstriction (immediately)
- platelet adhesion (seconds)
- platelet aggregation (minutes) =
> broken vessel, rough surface (collagen exposed)
> platelets stick to it and other platelets
> release a variety of substances (ADP)
POSITIVE FEEDBACK

26

Coagulation

Clotting factors in plasma:
- inactive form produced in liver
- one factor activates the next
= reaction cascade
THROMBIN
fibrinogen ------------------->> Insoluble fibrin
polymerisation

27

Coagulation pathways

EXTRINSIC pathway = very fast
- factors released by tissues start it
INTRINSIC pathway
- factors found only in blood cause it
+ occur together, converge in a common pathway, calcium required for both

28

Coagulation factors

Factor 1 = fibrinogen
Factor 11 = prothrombin
Factor 111 = thromboplastin
Factor IV = Calcium
Factor VIII = anti-haemophiliac factor A

29

How does a blood clot stop?

Platelets release chemicals to inhibit clotting
Other substances eg. heparin also inhibit process
Clot dissolves = fibrinolysis
Plasmin = fibrin -dissolving enzyme/clot buster

30

What are clots not formed all the time?

- platelets don't stick to smooth vessel wall
- clotting factors diluted by rapid blood flow (slow blood flow = DVT)
- natural anticoagulants present in the blood
> anti-thrombin produced by the liver
> heparin secreted by basophils and mast cells

31

Blood groups

Antibodies in plasma cause agglutination in mismatched blood transfusions
- don't have antibodies that would react with your antigens

32

ABO system

Group Antigen Antiobody
A A Anti-B
B B Anti-A
AB A&B None
o None Anti-A and Anti-B

33

RH group

D antigens on RBCs
Anti-D body not normally present
- forms only after exposure to Rh+ blood
- pregnancy, transfusion
O- packed cells can be given to any individual

34

What could happen in a mismatched transfusion reaction?

Agglutination = blockage of vessels
Haemolysis = free Hb can block kidney tubules and cause death

35

Haemolytic disease of newborn

Causes severe anaemia and toxic brain syndrome (excess bilirubin)
Prevention:
- blood typing of pregnant women
- Anti-D immunoglobulin given during pregnancy, after delivery, within 3 days of birth