Human Anatomy Ch.20 Part 2

Leukocytes (WBC)

only formed element that is complete cell with nuclei and organelles

Normal Range for Leukocytes

4800 to 10800 per blood (5 to 11k)

Diapedisis

The process by which white blood cells can leave capillaries

Leukocytes move through tissue spaces by

ameboid motion and positive chemotaxis

positive chemotaxis

guides WBCs to invading pathogens, damaged tissues, how they find where they need to go

"chemical roadmap"

Leukocytosis

WBC count over 11,000/mm3

-Normal response to infection

2 major categories of leukocytes

granulocytes and agranulocytes

Granulocytes

contain visible cytoplasmic granules (neutrophils, eosinophils, basophils)

-larger and short lived than RBCs and all are phagocytic to some degree

Agranulocytes

do not contain visible cytoplasmic granules (lymphocytes, monocytes)

Mnemonic to remember decreasing abundance in blood

Never Let Monkeys Eat Bananas

-Neutrophils, Lymphocytes, Monocytes, Eosinophils, Basophils

Neutrophils

Most numerous WBCs, w/ granules that stain with both acid and basic dyes containing either hydrolytic enzymes or antibacterial proteins

-3-6 lobes

Another name for neutrophils

polymorphonuclear leukocytes (PMNs) because nucleus is lobular

Function of Neutophils

phagocytosis referred to as "bacteria slayers" killing microbes by the process called respiratory burst

Respiratory burst (neutrophils)

cell synthesizes potent oxidizing substances (bleach or hydrogen peroxide)

Defensin granules (neutrophil) merge with __________________.

phagosome to form spears that pierce holes in the membrane of ingested microbe

Eosinophils

Red-staining granules that contain digestive enzymes that are released on large parasitic worms, digesting their surface

- also playing a role in allergies and asthma

Eosinophils physical characteristics

nucleus has 2 lobes connected by a broad band of DNA

Basohils

rarest WBC with large, purplish black granules that contain histamine

Histamine

inflammatory chemical that acts as a vasodilator and attracts other WBCs to inflamed sites

Lymphocytes

white blood cells crucial to immunity, found in lymphoid tissue (ex. lymph nodes, spleen), but a few circulate in blood

Lymphocytes physical characteristics

Large, dark purple, circular nuclei with thin rim of blue cytoplasm, about the same size as RBC

T lymphocytes (T cells)

act against virus-infected cells and tumor cells (many different ones)

B lymphocytes (B cells)

give rise to plasma cells (and B memory cells), which produce antibodies

Monocytes

white blood cells that leave circulation, enter tissues, and differentiate into macrophages

Monocytes physical characteristics

largest of all leukocytes, w/ an abundant pale blue cytoplasm that has U or kidney shaped nuclei

Macrophages

Actively phagocytic cells; crucial against viruses, intracellular bacterial parasites, and chronic infections

Leukopoiesis

production of white blood cells, stimulated by chemical messengers from the red bone marrow and mature WBCs

Two chemical messengers used in leukopoiesis?

Interleukins (numbered) & Colony stimulating factors (CSFs) (named for WBC type they stimulate)

-signaling the pathway the cells will enter for production

All leukocytes originate from

hemocytoblast stem cells

2 branches of the hemocytoblast stem cell for leukocytes

Lymphoid stem cells

Myeloid stem cells

lymphoid stem cells

produce lymphocytes

myeloid stem cells

produce all other elements except lymphocytes

Right before mature granulocytes the cells are

Band cells, forming a curved arc

Mature granulocyte

nuclei become segmented before being released in blood

are there more WBCs formed or RBCs?

there are 3x more WBCs formed than RBCs, because WBCs have a shorter life, cut short by fighting microbes

Monocytes are derived from

myeloid line, and some mature into macrophages that reside in tissues and engulf pathogens

-can live several months

Monocyte production order

monoblast to promonocyte to monocyte

Lymphocytes are derived from

lymphoid line

-live from a few hours to decades

T lymphocyte precursors

give rise to immature T lymphocytes that mature in thymus

B lymphocyte precursors

give rise to immature b lymphocytes that mature within bone marrow

Platelet

fragments of larger megakaryocyte

-not a cell only fragments of a cell

chemicals involved in clotting process

Serotonin, calcium, enzymes, ADP, platelet-derived growth factor

function of platelets

form temporary platelet plug that helps seal breaks in blood vessels

Circulating platelets are kept inactive and mobile by

nitric oxide (NO) and prostacyclin from endothelial cells lining blood vessels so we don't randomly form blood clots

Platelet formation is regulated by:

Thrombopoietin (TPO)

Platelets are formed in myeloid line from

megakaryoblast (stage I megakaryocyte)

What happens during platelet formation?

mitosis occurs but no cytokinesis, resulting in large stage 4 cell with multilobed nucleus that will cause projections to break off into platelet fragments

Normal range for platelets

150,000-400,000/ml of blood

Hemostasis

fast series of reactions for stoppage of bleeding; requires clotting factors and substances released by platelets and injured tissues

3 steps involves involved in hemostasis

Step 1: Vascular Spasm

Step 2: Platelet plug formation

Step 3: Coagulation (blood clotting)

Vascular spasm

Vessel responds to injury with vasoconstriction, can significantly reduce blood flow until other mechanisms an kick in

-most effective in smaller blood vessels

vascular spasms are triggered by

-Direct injury to vascular smooth muscle (break in vessel)

-Chemicals released by endothelial cells and platelets

-Pain reflexes

platelet plug formation

Platelets stick to collagen fibers that are exposed when vessel is damaged, the do not stick to intact vessel walls because collagen is not exposed

-could have a successful stoppage of blood at this step for small vessel tears but larger breaks need additional step

prostacyclins and nitric oxide

secreted by endothelial cells act to prevent platelet sticking

von Willebrand factor

helps to stabilize platelet-collagen adhesion when you have a break

When platelet plug formation is activated, platelets

swell, become spiked and sticky, and release chemical messengers

Chemical messengers released by platelets during platelet plug formation

ADP, Serotonin, and Thromboxane A2

ADP (adenosine diphosphate)

causes more platelets to stick and release their contents

serotonin and thromboxane A2

enhance vascular spasm and platelet aggregation (clumping or clustering)

What kind of cycle is the platelet plug formation?

positive feedback cycle, as more platelets stick, the release more chemicals which causes more platelets to stick and release more chemicals

Coagulation

blood clotting that reinforces platelet plug with fibrin threads that form a mesh that traps red blood cells and platelets

-effective for dealing larger vessel breaks

Procoagulants

clotting factors used in coagulation, mostly plasma proteins

Clotting factors are numbered in

oder of discovery, 1-13

What is needed to synthesize 4 of the clotting factors

Vitamin K

Phase 1 of coagulation

initiated by two pathways (intrinsic or extrinsic) to prothrombin activator, triggered by tissue damaging events ending with the activation of factor 10, involving a series of procoagulants

Factor 10 then complexes with calcium, PF3 (platelet factor 3) and factor 5 to form

prothrombin activator

Intrinsic pathway of coagulation

clotting factors are present within the blood that is activated by exposed collagen

-triggered by negatively charged surfaces such as activated platelets, collagen, or even glass of a test tube

extrinsic pathway of coagulation

factors needed for clotting are located outside blood

-faster pathway because it bypasses several steps

extrinsic pathway of coagulation is triggered by

tissue cell trauma exposes the blood to Tissue Factor (factor 3)

Prothrombin activator converts (phase 2 of coagulation)

prothrombin (inactive) to active enzyme thrombin

Thrombin

converts inactive fibrinogen to active fibrin

Fibrin

Protein strands that form the basis of a blood clot, causing plasma to become a gel like trap catching formed elements

Thrombin (along with Ca2+) activates

Factor XIII (fibrin stabilizing factor) that cross links fibrin and strengthens and stabilizes the clot

what chemical is important in blood clotting?

calcium

Where are majority of blood clotting factors located?

liver, so if you have liver issues your susceptible to bleeding

when damage has been repaired clot must be

stabilized and removed

clot retraction

contraction of actin and myosin platelets pulls on fibrin strands squeezing serum from clot drawing ruptured blood vessel edges together

-vessel is healing even as clot retraction occurs

Serum

plasma minus clotting proteins

Platelet-derived growth factor (PDGF)

stimulates division of smooth muscle cells and fibroblasts to rebuild blood vessel wall

-released by platelets

Vascular endothelial growth factor (VEGF)

stimulates endothelial cells to multiply and restore endothelial lining

Fibrinolysis

Process whereby clots are removed after repair is completed

-breakdown of fibrin

Plasminogen

a inactive plasma protein that is trapped in clot and converted to plasmin

Plasmin

an active fibrin-digesting enzyme

tissue plasminogen activator (tPA)

Factor XII and thrombin all play a role in conversion process of converting plasminogen to plasmin

-"clot buster"- given in stroke patients

cardiovascular system minimizes effects of blood loss by

1. reducing volume of affected blood vessels (vasoconstriction)

2. stepping up production of RBCs

-but can only compensate for so much

Loss of 15-30% of blood causes

pallor and weakness

loss of more than 30% of blood results in

potentially fatal severe shock

Low blood volume may result in

death from shock

When there's low blood volume, that volume must be replaced immediately with

Normal saline (salt lev. in body fluid) or multiple electrolyte solution (Ringers Solution) that mimics plasma electrolyte composition

Infusions of Packed Red Blood Cells (PRBCs)

(plasma and WBCs removed), are preferred to restore oxygen-carrying capacity

shelf life of blood is about...

35 days

blood typing

-Donor blood is mixed with antibodies against common agglutinogens (antigens)

-If agglutinogen (antigen) is present, clumping of RBCs will occur

-Blood is typed for ABO and for Rh factor in same manner

Antigens

anything perceived as foreign that can generate an immune response

Agglutinogens

Antigens formed on the surface of red blood cells that promote agglutination (clumping) if mismatched blood is transfused

Mismatched transfused blood

perceived as foreign and may be agglutinated and destroyed (potentially fatal reaction)

Antigens of ABO and Rh blood groups cause

most vigorous transfusion reactions, therefore they are major groups typed

Anti-A or anti-B antibodies

act against transfused RBCs with ABO not present of recipients RBCs

-preformed

universal recipient

Type AB: no anti-A or anti-B antibodies

universal donor

Type O: no A or B antigens

Rh+ indicates presence of

D antigen