Blood Flashcards
What are the functions of blood?
Transport - gases, waste products of metabolism, hormones, enzymes, nutrients.
Maintain body temp
Regulates blood clotting
Controls pH (buffer) - 7.35-7.45
What is bloods 4 components?
Plasma (complex Liquid) 55%
Erythrocytes (RBCs) 44%
Leukocytes (WBCs) 1% with platelets
Thrombocytes (platelets) 1% with WBC
Blood makes up 8% total body weight, 5L females and 5.5L males.
How is blood looking in a test tube?
RBCs are the heaviest so they sink to the bottom of the tube. Their volume is known as haematocrit and is 42% women and 45% man. If the haematocrit reduces, there is a risk of developing anaemia.
The middle layer in the test tube is called the buffy layer and consists of the WBCs and Platelets. The top layer is the plasma made up of soluble materials (mostly water).
What is the function of blood plasma?
It transports materials in the blood. Water has the capacity to hold heat, which is a product of metabolism, any heat not required for maintaining the body temperature is lost to the environment as the blood moves to the skin.
How is blood plasma composed?
90% is water. It has 8% plasma proteins and the rest consists of nutrients like AAs, glucose and vitamins. It also consists of waste products like bilirubin, which in excessive amounts causes jaundice. It also contains dissolved gasses.
Plasma proteins are identified through a process called electrophoresis which separates out the plasma.
What is the function of erythrocytes (RBCs)?
They transport oxygen. It is adapted for this by having a biconcave shape (dip in centre) allowing for more surface area for diffusion. It is also very thin allowing diffusion to happen rapidly.
How is haemoglobin in RBCs composed?
Globin: protein made of four chains. There are several forms of the chains, alpha, beta, gamma and delta. Most adults (97%) have 2 beta and 2 alpha - called HbA. 2.5% adults have 2 alpha and 2 delta - called HbA2.
Haem: each globin is attached to a haem group, so there are four haems. A haem group is a porphyrin ring containing one atom of iron, therefore there are four atoms of iron in each haemoglobin molecule.
What are the two types of RBCs identified to cause anaemia?
The mean cell volume is an important clinical index. Small RBCs (microcytic) are found in iron deficiency anaemia, and large RBCs (macrocytic) are found in folate deficiency anaemia.
What is irons function in haemoglobin?
Each iron molecule can combine reversely with one oxygen. So, one haemoglobin molecule can pick up 4 oxygen. Oxygen is poorly soluble in plasma, therefore 98.5% of oxygen is combined loosely to haemoglobin (oxygenation). Oxygen bound to a haemoglobin is called oxyhaemoglobin.
How is partial pressure of oxygen (pO2) related to haemoglobin?
During exercise, pO2 decreases, therefore haemoglobin will release more O2. In resting tissues, only 25% O2 is released from haemoglobin.
What are abnormalities of Hb production?
Haemoglobinopathies - these are abnormal globin chains that result in sickle cell anaemia. The coding of the beta chain is mutated where glutamic acid is replaced by valine. The HbS is formed and has a sickle shape. This causes them to become trapped in small vessels and cause a blockage. This therefore deprives downstream tissues of oxygen and leads to ischemia and infarction.
What is haemostasis?
This is the arrest of bleeding from a broken blood vessel - the stopping of a haemorrhage. A break in the vessel can occur due to a greater pressure in the vessel than outside, causing the blood to be pushed out.
How are blood platelets composed and what is their function?
They are small cell fragments that have budded off outer edges of large bone marrow cells called megakaryocytes.
What are the three steps of haemostasis?
Vascular spasm, Platelet plug, Blood clotting.
What happens in the vascular spasm step of haemostasis (first step)?
This is the contraction of a blood vessel. The smooth muscle layer surrounding the torn section of the vessel constricts to restrict blood flow and minimise blood loss. Damaged cells and platelets at the sight of the rupture release potent vasoconstrictors such as serotonin and ADP. As the ends of the endothelial (inner) tissues are brought together by the spasm, they become sticky and adhere to each other. Vasoconstriction is only a temporary resolution to a rupture in a blood vessel.
