Chp 28-Structure & Function of the hematologic system Flashcards
RBC does what
Provides oxygen and remove carbon dioxide
Composition of blood
92% water and 8% dissolved substances. Blood volume amounts to about 6 quarts (5.5L)
Chief functions of blood
1-deliver substances needed for cellular metabolism in tissues.
2-Removal of wastes of cellular metabolism
3-Defense against invading micro-organisms and injury
4-Maintenance of acid-base balance.
Plasma
- Aqueous liquid containing a variety of organic and inorganic elements.
- 50-55% of the blood volume
- Concentration of the materials is dependent on diet, metabolic demand, hormones and vitamins
- Plasma proteins: Albumin and globulins-which most are produced by the liver
Albumin
Carrier molecule for normal components of blood as well as drugs that have low solubility in water (e.g fatty acids, lipid-soluble hormones, thyroid hormones, bile salts).
- Most essential role is regulation or passage of water and solutes through capillaries
- Large and don’t diffuse freely-hence the colliodal osmotic pressure that regulates passage of water and solutes for surrounding tissues
- Draws fluid from intravascular to the blood vessels (useful for shock, burns, surgeries, serious injuries)
Other plasma proteins
- Globulins 38%
- Fibrinogen 4%
- Prothrombin 1%
- Plasma proteins can also be classified based on function: clotting, defense, transport, or regulation
Cellular components of blood: Erythrocytes
RBCs: most abundant cells of the blood-primarily responsible for tissue oxygenation
- Contains hemoglobin
- Limited lifespand (100-120 days)
- Removed from circulation by the spleen to be replaced by new erythrocytes
RBC shape
- Biconcave
- Reversible deformed
Leukocytes
WBCs
- Act primarily in the tissues but are transported in the circulation (5000-10,000)
- Classified by structure as either granulocytes or agranulocytes and according to function as phagocytes or immunocytes.
Granulocytes
Neutrophils, basophils and eosinophils (all are phagocytes)
- Also mast cells
- Have membrane bound granules in the cytoplasm. Contain enzymes that kill. Also contain biochemical mediators with inflammatory and immune functions
Agranulocytes
- monocytes and macrophages (phagocytes)
- whereas lymphocytes are immunocytes (cells that create immunity)
Neutrophils (PMN)
Most numerous
- Reach a fully mature state in the bone marrow.
- Normally takes 14 days to develop but accelerated according to infection and treatment w/ colony stimulating factors.
- Chief phagocyte for early inflammation
- Die within 1-2 days after use.
Eosinophils
- Ingest antigen-antibody complexes and viruses.
- Attack parasite and other pathogens
- Contain toxic chemicals
- Type 1 hypersensitivity reactions-allergic reactions (inflammatory state from lungs or people with asthma is common)
Basophils
- Abundant mixture of biochemical mediators, including histamine, chemotactic factors, proteolytic enzymes, leukotrienes and cytokines.
- Increase in numbers to allergic inflammatory reactions and parasitic infections (ticks).
- B cell differentiated driven with plasma cells that secrete IgE
- secrete heparin
Mast cells
- highly similar to basophils
- Reside in vascularized connective tissue just beneath the body epithelial surface-GI and respiratory tracts-central roles in inflammation
Macrophages
- remove old and damaged cells and large molecular substances from blood. (damaged RBCs, platelets-removed from spleen, dead neutrophils.
- Initiate wound healing
Lymphocytes
reside in secondary lymphoid tissues as mature T and B cells and plasma cells
Platelets
- Thrombocytes: Blood coagulation
- An additional 1/3 of bodies available platelets reside in the spleen (300 mL).
Lymphoid organs
- Primary: Thymus, bone marrow
- Secondary: spleen, lymph nodes, tonsils, peyer patches in the ileum of the small intestine.
Spleen
-Site for fetal hematopoiesis, filters blood-borne antigens, cleanses blood through the action of mononuclear phagocytes, initates immune responses to blood borne microorganisms, destroys ages RBCs, and reservoir for blood.
Composition of spleen
- Located on left upper abdomen and curved around the stomach
- Lymphoid follicles consist primarily of B lymphocytes-chief sites of immune function
- Venous sinuses-red pulp-storing more than 300mL of blood. (sudden drop in BP cause SNS to stimulate constriction of sinuses, resulting in expulsion of as much as 200mL in the venous circulation-increases hct by as much as 4%)
- White pulp contain the areas of masses of lymphoid tissue containing macrophages and lymphocytes (primarily T lymphocytes).
Splenectomy
Immune response decreased to encapsulated bacteria (Streptococcus pneumoniae, neisseria meningitis)
Lymph nodes
-Primary site for the first encounter between antigen and lymphocytes