Blood and Formed Elements Study Guide

A comprehensive vocabulary review set covering the functions, components, formation, lifecycle, and cell types of blood from the study guide notes.

Functions of Blood

Transport, Regulation, and Protection (including the transportation of nutrients, wastes, and fluids, as well as the regulation of pH and metabolic wastes).

Formed Elements

The cellular components of blood, which consist of erythrocytes (red blood cells), leukocytes (white blood cells), and thrombocytes (platelets).

Hematopoiesis

The formation of all blood cells, which occurs in red bone marrow via loose reticular connective tissue and sinusoidal capillaries.

Erythrocytes

Red blood cells; biconcave discs that lack a nucleus and organelles to increase surface area-to-volume ratio and flexibility, functioning primarily in gas transport ($O_2$ and transporting $CO_2$ waste back to the lungs).

Hemoglobin

A protein composed of $4$ globin proteins (polypeptide chains) and red heme pigment, capable of transporting $4$ molecules of $O_2$ per Hb molecule.

Transferrin

A blood plasma protein synthesized in the liver that binds and transports potentially toxic free iron through the bloodstream.

Erythrocyte Life Span

$100\text{--}120\text{ days}$; erythrocytes cannot synthesize proteins, grow, or divide because they are anucleate, leading to engulfment and breakdown by macrophages in the spleen.

Bilirubin

A yellow pigment formed from the degradation of heme that is transported to the liver and secreted via bile into the small intestine.

Stercobilin

A brown pigment degraded from urobilinogen in the digestive tract that is eliminated from the body in feces.

Leukocytes

White blood cells comprising about $1\%$ of total blood volume that function in the immune system to fight against disease.

Granulocytes

A class of white blood cells that are larger and shorter-lived than red blood cells, are all phagocytic, and function to minimize the spread of pathogens and prevent over-inflammation.

Neutrophils

The most numerous white blood cells ($50\%\text{--}70\%$ of WBCs), featuring a $3\text{--}6$ lobed nucleus and active phagocytic capabilities via respiratory burst.

Eosinophils

Granulocytes comprising $2\%\text{--}4\%$ of WBCs with a bilobed nucleus and red granules containing digestive enzymes that act against large parasitic worms and play a role in allergies and asthma.

Basophils

The rarest white blood cells ($0.5\%\text{--}1\%$ of WBCs), containing a deep purple nucleus with $1\text{--}2$ constrictions and purplish/black granules filled with histamine and inflammatory vasodilator chemicals that attract WBCs.

Agranulocytes

White blood cells lacking visible cytoplasmic granules, which include lymphocytes and monocytes.

Lymphocytes

The second most numerous WBCs, characterized by a large, dark purple nucleus with a thin blue rim (halo); primarily found in lymphoid tissue (lymph nodes, spleen) and essential to immunity (T and B cells).

Monocytes

The largest WBCs ($3\%\text{--}8\%$ of WBCs), featuring abundant pale blue cytoplasm and a kidney- or U-shaped nucleus; they leave circulation to differentiate into actively phagocytic macrophages and serve as antigen-presenting cells.

Thrombocytes

Platelets; cell fragments numbering $150\text{--}400\text{k}$ per $\mu\text{L}$ of blood that contain various chemical substances.

Types of anemias

Hemorrhagic anemia

iron deficiency anemia

renal anemia

pernicious anemia

thalassemias

sickle cell anemia

Polythycemias

Polycythemia

Polycythemia vera

Secondary polycythemia

Formation of platelets

Megacaryocyte, cytoplasmic projections, lumen of capillary, breaks into platelet fragments

Steps of hemostasis

1.Vascular spasm

2. Platelet plug

3. Coagulation

What is hemostasis?

series of reactions for stoppage of bleeding

Vascular spasm

vasoconstriction resulted by damaged or direct injury to vascular smooth muscle

Platelet plug

-positive feedback cycle

-damaged endothelium exposed collagen fibers and platelets stick to collagen fibers via plasma proteins

Coagulation

-reinforced platelet plug with fibrin threads

-local blood transformed liquid to gel

-Vitamin k needed to synthesize 4 factors

Steps of coagulation

1. Prothrombin activator formed via intrinsic and extrinsic pathways

2. Prothrombin converted to enzyme thrombin

3. Thrombin catalyzes fibrinogen to fibrin

Ingredients for prothrombin activator

activated X, Activated V, Calcium and PF3

Clot retraction

• Actin & myosin in platelets contract w/in 30-60 seconds

• contraction pulls on fibrin strands, squeezing serum from clot

• draws ruptured vessel edges together (tight stitches)

Clot stabalization

• vessel healing simultaneously as clot retraction occurs

• Platelet derived growth factor released by platelets

• Stimulates division of smooth muscle cells & fibroblasts to rebuild blood vessel walls

Fibrinolysis (clot removal)

• begins within 2 days of clot formation & continued for several days until dissolved

• Plasma protein plasminogen (inactive)

• Activated into plasmin (active) = fibrin digesting enzyme

Disorders of hemostasis

• Thrombus

• Embolus

• Embolism

Thrombus

clot that persist in unbroken blood vessel (may block blood circulation)

impaired blood flow

Embolus

if clot breaks away and floats freely in blood

Embolism

When embolus encounters vessel too narrow

Risk factors of hemostasis disorders

atherosclerosis, inflammation, slowly flowing blood, or blood stasis from immobility