Lecture 13 - Composition and General Functions of blood

Question 1

Three general functions of blood

Answer 1

Transport
Immune response
Coagulation

Question 2

Transport

Answer 2

Blood transports materials within it through the body

Oxygen, water and nutrients
Carbon dioxide and waste products
Ions associated with pH and homeostasis (Ca2+, H+ gradient)
Heat - a product of oxidative reaction in cells (water good absorbing heat)
Hormones - coordinate the activities of organs of the body
Immune cells and coagulation factors

Question 3

Immune response

Answer 3

For fighting infection and production of the immune response
Largely via white blood cells

Not the first line of defense, that’s skin
This acts when pathogens get through the skin barrier and into the body

Question 4

Coagulation

Answer 4

For preventing bleeding
Via platelets and ‘coagulation factors’ in plasma
-stop leak of blood by preventing more blood leaving and preventing more pathogens

Question 5

Composition of blood

Answer 5

Roughly 50:50 plasma and formed elements (plasma 55% and formed elements 45%)

Question 6

Plasma

Answer 6

55%
Almost all water (92%)and the other things in plasma are proteins and solutes with various functions
Plasma proteins(7%) - some functions of these include…maintains osmotic presssure, immune response, coagulation factor, enzymes and hormones have lots of functions
Other solutes (1%) -some functions of these include…maintain pH and ion balance, cells need organic nutrients to function, cells are getting rid of organic wastes
Water (92%) can hold a lot of heat

Question 7

Formed elements

Answer 7

Cells or cell like pieces that are primarily in the blood
45%
Platelets - less than 1%, cell fragments that participate in clotting to stop bleeding, not a cell - it is a cell fragment of a cell that expanded so much and exploded
White blood cells - less than 1%, immune response and defense mechanisms; these seek and destroy invading pathogens (neutralise invading bodies and removes them from the body)
Red blood cells - 99.9%, by far the most common cell type found in the blood, highly specialised for transport of oxygen

Question 8

Erythrocytes are

Answer 8

Red blood cells

Question 9

Platelets

Answer 9

cell fragments that participate in clotting to stop bleeding, not a cell - it is a cell fragment of a cell that expanded so much and exploded

Question 10

Hematopoesis

Answer 10

Hematopoesis is the formation of blood cells made out of the hemocytoblasts

Initiated in the bone marrow which contains hemocytoblasts (progenitors)

Question 11

Hemocytoblasts

Answer 11

Hemocytoblasts are the progenitors for all blood cells

Make up the formed elements, do not make up anything that is present in the plasma

Question 12

What does erythropoietin (EPO) do?

Answer 12

hormone that the kidneys produce to stimulate production and maintenance of crucial red blood cells.

Question 13

Biconcave disc shape of red blood cells

Answer 13

Round in shape with a depression in it

Gives the red blood cells…
Large surface area:volume ration - for transport of gas and the depression gives extra surface area for gas movement
Allows for efficient diffusion of gases (oxygen and carbon dioxide)
Flexibility for movement through the narrow capillaries - no points or jagged points, no hard edges so won’t get stuck

Question 14

Structure of red blood cells

Answer 14

No nucleus, all come from a common progenitor so don’t need to divide

Contain large amounts of haemoglobin
1/3 weight of the RBC
Uses iron as part of the heme structures to bind oxygen
4 heme units, so each haemoglobin can bind 4 oxygen molecules since there are 4 iron atoms

Question 15

Hematocrit or Packed Cell Volume (PCV)

Answer 15

Centrifuged blood separates into its main components - heavy cells towards the bottom, plasma and WBCs are higher up

THe fraction of blood that is occupied bu the red blood cells is called the hematocrit or packed cell volume (PCV)

Men tend to have a higher level but this is no guarantee as it is dependent on exercise training

Question 16

Normal hematocrit

Answer 16

about 50%

Question 17

Anemic hematocrit

Answer 17

Few RBCS in the system compared to plasma and WBCs

Attributed with iron deficiency, lower binding efficiency for oxygen

Under 50%

Question 18

Polycythemic hematocrit

Answer 18

The presence of an abnormally high number of red blood cells in the circulating blood. So the blood is so thick due to the high amount of RBCs. This affects blood pressure by increasing it which causes strain of the heart

Over 50%

Question 19

Erythropoiesis

Answer 19

Generation of red blood cells

All blood cells are derived from a common progenitor cell
RBC production stimulated by erythropoietin (EPO) (this stimulates RBC formation when it is circulating in the body)
Requires iron to make hemoglobin

Question 20

Why do athletes train at high altitude?

Answer 20

RBC production controlled by homeostatic mechanism involving erythropoietin (EPO)
Augmented by testosterone
Reduction in RBCs causes a decrease in oxygen delivery - sensed by kidneys

More exercise = more oxygen needed. Less oxygen in the air and training hard so the body senses low oxygen and releases EPO into the system to generate more RBCs - jumpstarts the RBC formation

Oxygen load starts to fall, kidneys sense this, release EPO into the blood, circulated around until it reaches bone marrow causing haemocytoblasts which causes RBCs to be formed hence more haemoglobin hence more oxygen

Question 21

Testosterone and erythropoiesis

Answer 21

Combination of EPO and testosterone increases RBCs

Question 22

Basic flow chart of RBC formation

Answer 22

Erythropoietin - erythrocytes - increased oxygen capacity - increased performance

Question 23

Risk of EPO infusions

Answer 23

Tricking you body into making more red blood cells gives you a higher risk of cardiovascular disease