Basal Humanbiologi Blod

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Basal Humanbiologi

8. Blod

8-1. Beskrive blodets sammensætning i hovedtræk.

8-2. Gøre rede for livscyklus og betydningen af erythrocytter

for blodets gastransport og pH-homeostase, og for thrombocytternes, thrombins og fibrins oprindelse og betydning for blodets koagulationsevne.

Hemopoiesis: Before birth: yolk sac, liver, spleen. After birth: red bone marrow. Lifespan: 120 days, no nuclei, can’t synthesize protein, divide.


pH homeostasis: chemistry stuff.

fibrin: plasma protein, see section 3.
thrombin: prothrombin = alpha globulin (plasma protein) => thrombin.
throbocyte: Hemocytoblast → megakaryoblast → megakaryocyte → thrombocytes (platelet). In response to hormone thrombopoietin, life cycle 10 days, normal count 130k – 360k mm-3.

Blood coagulation

Homostasis: stoppage of bleeding. Blood vessel spasm, platelet plug formation, blood coagulation.
Vasospasm: smooth muscle contract few min, effect 30 min, due serotonin released from platelets.
Plug formation: Positive feedback . Platelets adhere to exposed collagen, release cytoplasmic gruanle, contain serotonin; ADP, attracts more platelets; thromboxane promotes platelets aggregation; more platelets.
Coagulation: activated by clotting factors, some promotes, inhibits, result depends on balance, normally prevail. Damaged tissue release thromboplastin → produce prothrombin activator (depends on Ca+m phospholipids conc.) → prothrombin (ά globulin) ά thrombin → catalyse fragment of fibrinogen → fibrin → create meshwork → entrap erythrocyte, platelet. (many steps are security effect)

Clot Formation

Stage 1: Damage to tissue or blood vessels activates clotting factors that activate other clotting factors, which leads to the production of prothrombinase. The activated factors are within white ovals, whereas the inactive precursors are shown as yellow ovals. See the next screen for the two pathways.

Stage 2: Prothrombin is activated by prothrombinase to form thrombin.

Stage 3: Fibrinogen is activated by thrombin to form fibrin, which forms the clot.
Stage I can be activated in two ways:
Extrinsic pathway is initiated when clotting factors are released by the damaged blood vessel and perivascular tissue (i.e., the factors come from sources other than the blood).
Intrinsic pathway is initiated when factor XII is activated or released when platelets degranulate (i.e., everything needed to initiate the pathway is present in the blood or platelets).

8-3. sammensætningen og betydningen af plasmaets proteiner

(derunder deres betydning for substanstransport i plasma) og elektrolytter


  • 7% protein
    • Albumins 60%
    • Globulins 36%
    • Abrinogen 4%
  • 92% water
    • 1% solutes (electrolyte, waste, water products, gases, lipids, hormone, carbohydrates)


Plasm Function Source
Water (90-92%) Maintain blood volume; transports molecules Absorbed from intestine
Plasma proteins (7-8%)
A: smallest, 60%, maintain blood volume, colloid osmotic pressure, plasma protein too large to pass through capillary walls, create osmotic pressure, hold water in the capillaries, despite blood pressure tends to force water out by filtration.
G: 36%, ά + β transport lipids, fat-soluble vitamin. γ antibody
F: largest, blood coagulation
A: Liver

G: Liver => ά + β
Lymphatic tissue => γ
F: liver


Lack of plasma protein:
starvation, protein-deficient diet, impaired liver cannot synthesize
→ conc.plasma protein drops → colloids osmotic pressure drops → fluid to intercellular spaces → edema