Cardiovascular System 1 Flashcards
Describe the functions of blood
- Transport of dissolved substances (O2, CO2, waste products, hormones)
- Regulation of pH and ions (absorbs & neutralizes lactic acid to avoid issues in the body)
- Restriction of fluid losses at injury sites (Blood clotting)
- Defense against toxins and pathogens (WBCs (White blood cells) attack/remove/engulf pathogens)
- Stabilization of body temperature (Absorbs heat from active muscles & distributes to other tissue)
List the characteristics of blood
- Blood volume (Male 5-6 litres & Female 4-5 litres)
- Blood is highly viscous, slightly alkaline (7.35-7.45), temp 38°C (100.4°F)
- Blood consists of 55% plasma & 45% formed elements
- Hematocrit (Process to measure of % of RBC in whole blood)
Describe the formation of blood cells
Formed elements develop by Hematopoiesis (Hemopoiesis) in red bone marrow
Hemocytoblasts differentiate into:
- Myeloid stem cells (Give rise to RBC, platelets, eosinophils, basophils, neutrophils, monocytes)
- Lymphoid stem cells (Give rise to lymphocytes → Migrate to the lymphatic system to complete maturation)
Explain the importance of blood typing
- Cell surface proteins that identify cells to the immune system
- Normal cells are ignored, and foreign cells attacked e.g. if blood type A, A antigens are ignored but B antigens would be attacked.
- Can safely donate your blood or receive a blood transfusion
- Presence or absence of RBC surface antigens A, B or none, and Rh (or D) presence or absence
- Blood types (Genetically determined)
4 Basic blood types
- Type A (surface antigen A) has antibodies to B
- Type B (surface antigen B) has antibodies to A
- Type AB (surface antigens A and B) neither antibodies
- Type O (neither A nor B surface antigens) Antibodies to A and B
Describe the process of hemostasis
- Stopping of bleeding
The cessation of bleeding:
- Vascular phase
- Platelet phase
- Coagulation phase
First Phase of Hemostasis
The Vascular Phase
- The vascular spasm occurs (bleeding and damage vessels, contraction in blood vessels wall) – lasts up to 30 mins
- Contraction of the smooth muscle of damaged blood vessel wall caused by:
- Damage to smooth muscle & endothelial cells
- Activation of platelets → Release vasoconstrictors
- reflexes initiated by pain receptors
Second Phase of Hemostasis
The Platelet Phase
- Begins within 15 seconds after injury
- Platelet plug formation
- Platelets contact and adhere to damaged tissue in the blood vessel wall (attachment of platelets to sticky endothelial surfaces to the base membrane to expose collagen fibres)
- Platelets become activated
- Extend projections to attach to one another
- Positive feedback loop of aggregation
- Activated platelets release clotting compounds
- Plug size restricted by inhibitory compounds, negative feedback & formation of blood clot (isolation)
Third Phase of Hemostasis
Coagulation Phase
- Begins 30 seconds or more after the injury
- Clotting factors (e.g. liver enzymes, substances from platelets & damaged tissue) promote formation of prothrombinase
- Converts prothrombin (enzyme produced by liver) into thrombin
- Thrombin converts soluble fibrinogen into fibrin
- Fibrin forms threads which trap formed elements to form clot
Explain what hematocrit means? What does it tell us about someone’s blood?
Process to measure of % of RBC in whole blood
Male 47% (range of 40-54%)
Female 42% (range of 38-46%).
Identify what the formed elements are in our blood?
Erythrocytes (red blood cells)
Leukocytes (white blood cells)
Thrombocytes (platelets)
Function of Erythrocytes (red blood cells)
High surface-to-volume ratio
- quickly absorbs and releases oxygen
Each contains ~280 million haemoglobin molecules
- Transports O2 and CO2
- Bind oxygen per ion molecule
- Ion is essential to production to hemoglobin
Has no nucleus
- Always replacing
Discs bend and flex entering small capillaries
- Can bend and move through to not stuck
Function of Leukocytes (white blood cells)
Accumulate at sites of infection/inflammation
- Lymphocytes recirculate between blood and tissues
‘Emigrate’ from blood compartment
- Adhesion molecules on WBC and endothelial cells allow WBC’s to ‘stick’ to endothelium
Once at site of infection/inflammation WBC’s carry out various functions in the inflammatory/immune response
- E.g. phagocytosis or further release of histamine, etc.
Function of Thrombocytes (platelets)
Release important clotting chemicals
Temporarily patch damaged vessel walls
Actively contract tissue after clot formation
Explain how we know if an individual is rhesus positive or negative?
Rh Factor – refers only to the D antigen
Rh positive (Rh+) – presence of D surface antigen Rh negative (Rh-) – absence of D surface antigen
RBC – surface antigen A and Rh antigen → A+
