Module 1 - Blood

Leukocytes

White blood cells (WBCs)

Leukocyte function

Main defense inside the body → defend against invading microorganisms and defective body cells (old cells, cells with defective DNA, virus infected cells)

Characteristics of leukocytes

• Less abundant than RBCs

• Much larger than RBCs

• Only formed elements that are complete cells

• Much shorter lifespan than RBCs

Diapedesis

WBCs can leave capillaries or small blood vessels to perform defense functions in tissues

→ some WBCs leave the bloodstream to enter a tissue but remain fixed there instead of reentering the bloodstream

Chemotaxis

Process by which leukocytes are attracted o infection by nearby chemical signals

Granular leukocytes

Leukocytes that contain granules, produced in red bone marrow, have lobed nuclei

• Neutrophils

• Eosinophils

• Basphils

Agranular leukocytes

Leukocytes that lack granules

• Monocytes

• Lymphocytes

Neutrophils

Rapid responders to infections → bacterial and acute infections

• Granules stain light purple and are in the nucleus

• Nuclei have 2-5 lobes

• Capable of phagocytosis

• Most abundant leukocyte

Eosinophils

Granular leukocyte that is mainly involved in allergic reaction and parasitic infections

• Granules are large and stain red-orange color

• Nuclei have 2 lobes

• Capable of phagocytosis

Neutrophil granules

Lysozyme → enzyme to lyse bacteria cell walls

Defensins → proteins that puncture bacterial and fungal cell walls

Eosinophil granules

Antihistamine molecules → counteract histamine to balance inflammatory response

Molecules toxic to parasitic worms

Basophils

Granular leukocytes that intensify immune response → allergic reactions and inflammation

• Large granules that stain dark blue → can make it hard to see nucleus

• Nuclei have 2 lobes

• Release histamine and heparin

Basophils release…

Histamine → inflammatory chemical, vasodilator, attracts other WBCs

Heparin → opposes blood clotting

Monocytes

Agranular leukocytes that originate form myeloid stem cells that are a type of macrophage → chronic infections

• Large size and have a U-shaped nucleus

• Can leave circulation to enter tissues

• Help activate lymphocytes and engulf pathogens

Lymphocytes

Agranular leukocyte that arises from lymphoid stem cells

• There are 3 kinds: NK cells, B cells, and T cells

• Have large round nucleus with very little cytoplasm

• Initially form in bone marrow and mature in lymphatic tissues

Natural killer (NK) cells

Type of lymphocyte that recognizes non-self cells or abnormal surface proteins on cells and kills them locally

• Generalized, non-specific immunity because they don’t need prior exposure to act

• Identifies cells as cancerous or virus-infected

B lymphocytes (B cells)

Type of lymphocytes that form plasma cells that produce antibodies (Y-shaped proteins)

• Antibodies circulate in bloodstream and bind to pathogens to mark them for destruction

T lymphocytes (T cells)

Type of lymphocyte that kills virus-infected cells or tumor cells by secreting local toxins to kill cells directly

Platelets (thrombocytes)

Cell fragments (not true cells) that form clots and secrete growth factors for tissue growth and repair

• Cytoplasm fragments off of megakaryocytes (large bone marrow cells that produce platelets)

Megakaryocytes

Large cells with lobed nuclei in the bone marrow that produce platelets

• Release 2000-3000 platelets per lifetime

• Get phagocytized by macrophages after they have release all of their cytoplasm

Thromboprotein

Hormone secreted by the kidneys and liver to stimulate the growth of megakaryoblasts (cells that mature into megakaryocytes)

Hemostasis

Process where the body seals a rupture blood vessel to prevent further blood loss

Ending “-penia”

Too few of a type of blood cell

Ending “-cytosis”

Too many of a type of blood cell

Leukopenia

Too few WBCs being produced → can be caused by chemotherapy

• WBCs are the body’s main defense so not having enough leaves someone vulnerable to infection

• More susceptible to life-threatening complications

Leukocytosis

Too many leukocytes being produced

• Having too many means they aren’t being formed properly → you have a lot of them but they aren’t fully functional or working the right way

• Makes you vulnerable because WBCs aren’t killing pathogens like they should be

• More susceptible to life-threatening complications

Leukemia

Form of cancer caused by an abundance of leukocytes

• Leukocytes are not developed properly → a lot of them but they don’t work

Lymphoma

Form of cancer caused by cancerous B and T cells → malignant B and T cells begin to collect in the liver and the spleen, lymph nodes, and liver

• B and T cells don’t function properly leaving someone vulnerable to infection

Thrombocytosis

Too many platelets in circulation → blood clots more frequently than it should so blood clots form where they aren’t needed

Thrombocytopenia

Too few platelets in circulation → results in lack of clotting which can cause excessive bleeding

Process of Hemostasis

1. Vascular spasm

2. Formation of platelet plug

3. Coagulation cascade

4. Clot retention

Hemostasis: 1) vascualr spasm

Smooth muscle in vessel wall constricts to reduce blood flow after injury

• Occurs immediately after vessel wall is damaged or severed → endothelins are released by cells in vessel walls that trigger vasoconstriction

• Helps minimize blood loss

Hemostasis: 2) Formation of platelet plug

Platelets form a temporary seal to buy time for the body to make a more durable clot

• Platelets are activated and transition from being smooth to spiky → they clump together at the vessel opening and form a plug

• Platelets release chemicals

  • ADP → helps more platelets stick to injury site

  • Serotonin → helps maintain vasoconstriction and enhances platelet aggregation

  • PDGF (platelet derive growth factors) → attract cells called fibroblasts

Von Willebrand factor

Bridge between platelets and collagen so that the platelets stick to that area

Hemostasis : 3) Coagulation cascade

Series of clotting reactions that form fibrous network (fibrin mesh) that lays overtop platelets → reinforce the platelet plug

• Main goal is converting fibrinogen (soluble) into fibrin (insoluble) → done one of two ways

  • Intrinsic pathway

  • Extrinsic pathway

Intrinsic pathway (contact activation pathway)

Method of coagulation cascade has more steps and is more complex → gets completed in minutes

1. Factors in the blood activate factor XII → ex: exposed collagen in blood vessel

Clotting factors

Proteins in blood plasma circulating in the blood, ready but not active (must be activated)

• Part of coagulation cascade because an activated clotting factor activates more clotting factors

Where do clotting factors come from?

They are secreted by the liver

How many clotting factors are there?

12 known clotting factors

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