Mod1-Obj7: Role of blood in homeostasis

Question 1

Blood composition

Answer 1

Blood: A fluid connective tissue composed of

1. ) Plasma=90% water, proteins e.g.) albumin
2. ) Formed elements
   - Erythrocytes (RBC’s)
   - Leukocytes (WBC’s)
   - Platelets

Question 2

Composition of blood is under…

Answer 2

Homeostatic regulation

Question 3

Formed elements: Plasma

Answer 3

55% of whole blood, least dense component

Question 4

Formed elements: Buffy Coat=Leukocytes and Platelets

Answer 4

<1% of whole blood

Question 5

Formed elements: Erythrocytes

Answer 5

45% of whole blood, most dense component

Question 6

Haematocrit

Answer 6

Percent of blood volume that is RBC
-47%+-5% for males
-42%+-5% for females
=Average 45%

Question 7

Erythrocytes

Answer 7

-Red blood cells

Biconcave discs, anucleate, essentially no organelles (limited lifespan of up to 120 days)

Question 8

Structural characteristics of RBC contribute to gas exchange

Answer 8

• Biconcave shape
• Huge surface area to volume ratio
• Stack-ability
• > 97% haemoglobin
• Flexible shape

Question 9

Erythrocyte function

Answer 9

• RBC’s are dedicated to respiratory gas transport

- Haemoglobin binds reversibly with oxygen

Question 10

Haemoglobin (Hb)

Answer 10

-Large protein-binds 4 O2 molecules

Question 11

The chemical properties of Hb facilitate effective gas transport

Answer 11

1. ) O2 loading in the lungs
   - Produces oxyhaemoglobin (ruby red)
2. ) O2 unloading in the tissues
   - Produces deoxyhaemoglobin (dark red)
3. ) CO2 loading in tissues
   - Produces carbaminohaemoglobin (carries 20% of CO2 in blood)
4. ) CO2 unloading in the lungs

Question 12

Erythrocytes: Sickle cell anaemia

Answer 12

Altered Hb structure

• Poor O2 binding
• Sticky RBC that clog vessels

Question 13

Blood cell formation: Haematopoiesis

Answer 13

Gives rise to all blood cell types

-Occurs in red bone marrow of the axial skeleton, girdles, humerus and femur

Question 14

Erythroplesis

Answer 14

The production of red blood cells

Question 15

Regulation of erythropoiesis: Too few RBC

Answer 15

Tissue hypoxia (insufficient O2)

Question 16

Regulation of erythropoiesis: Too many RBC

Answer 16

Increases blood viscosity and blood pressure

Question 17

Balance between RBC production and destruction depends on…

Answer 17

1. ) Hormonal control-EPO from kidneys

2. ) Adequate iron, amino acids and B vitamins

Question 18

Old RBC become fragile and Hb begins to degenerate…

Answer 18

Engulfed and recycled by white blood cells in the spleen

Question 19

Leukocytes

Answer 19

White blood cells

• The only complete cells in the blood
• Primary function is defence against infection

Question 20

Formed elements of blood

Answer 20

1. ) Platelets
2. ) Leukocytes
3. ) Erythrocytes

Question 21

Formed elements: Differential WBC count

Answer 21

all total 4800-10,800 cells/ <1% total blood volume)

Question 22

Formed elements: Granulocytes

Answer 22

1. ) Neutrophils (50-70%)
2. ) Eosinophils (2-4%)
3. ) Basophils (0.5-1%)

Question 23

Formed elements: Agranulocytes

Answer 23

1. ) Lymphocytes (25-45%)

2. ) Monocytes (3-8%)

Question 24

Infection stimulates the release of WBC from the bone marrow

Answer 24

WBC count 11,000/ul

Question 25

Neutrophils and monocytes

Answer 25

Able to leave the blood vessels and move into the tissues to sites of tissue damage, infection or invasion
-Able to engulf (phagocytose) and destroy damaged and dead cells, and invaders e.g.) bacteria

Question 26

Lymphocytes

Answer 26

Found in the blood and lymphoid tissue

-Crucial to specific immunity, e.g.) antibody production

Question 27

Homeostasis: Normal blood oxygen levels

Answer 27

1. ) Stimulus: hypoxia (low blood O2-carrying ability) due to decreased RBC count, decreased amount of haemoglobin, decreased availability of O2
2. ) Kidney releases erythropoietin
3. ) Erythropoietin stimulates red bone marrow
4. ) Enhanced erythropoiesis increases RBC count
5. ) O2 carrying ability of the blood increases

Question 28

Platelets

Answer 28

Small fragments of megakaryocytes

• Formation occurs in the bone marrow and is regulated by a hormone- Thrombopoietin
• Granules contain chemicals involved in clotting e.g.) serotonin, Ca2+, enzymes

Question 29

Functions of blood can be categorised as

Answer 29

1. ) Distribution
2. ) Regulation
3. ) Protection

Question 30

1.) Blood is essential for the distribution of:

Answer 30

1. ) Oxygen and nutrients to body cells
2. ) Metabolic wastes to the lungs and kidney for elimination
3. ) Hormones from endocrine glands to target organs

Question 31

2.) Blood is involved in regulating and maintaining:

Answer 31

1. ) The composition of the interstitial fluid (i.e. electrolyte levels)
2. ) Body temperature by absorbing and distributing heat
3. ) pH using chemical buffers: blood pH 7.35-7.45
4. ) Adequate fluid volume in the circulatory system

Question 32

3.) Protective functions of blood

Answer 32

1. ) Infection control
   - WBC defence against foreign invaders
   - Lymphocytes produce antibodies
   - Anti-microbial proteins (e.g. complement)
2. ) Blood loss
   - Plasma proteins and platelets initiate clot formation to prevent blood loss and infection-involves positive feedback

Question 33

Platelets and blood clotting

Answer 33

Circulating platelets are normally kept inactive and mobile by chemicals produced by endothelial cells

Question 34

Haemostasis

Answer 34

Fast series of reactions for the stoppage of bleeding

Question 35

3 steps of Haemostasis

Answer 35

1. ) Vascular spasm
2. ) Platelet plug formation
3. ) Coagulation (blood clotting)

Question 36

Step 1 haemostasis: Vascular spasm

Answer 36

Smooth muscle contracts, causing vasoconstriction

Question 37

Step 2 heamostasis: Platelet plug formation

Answer 37

• Injury to lining of vessel exposes collagen fibres; platelets adhere
• Platelets release chemicals that make nearby platelets sticky; platelet plug forms

Question 38

Step 3 haemostasis: Coagulation

Answer 38

Fibrin forms a mesh that traps red blood cells and platelets, forming the clot

Question 39

Function of blood

Answer 39

The activities of the blood are essential in maintaining the conditions of the internal environment (ECF) within homeostatic limits so the cells (and proteins, e.g. enzymes) can function optimally