Unit I Endocrine System & Blood

Endocrine System:

• Define hormone: A chemical messenger secreted by glands to regulate body functions.

• How are paracrine hormones different? They act on nearby cells rather than distant targets.

• What is a target cell? A cell with receptors for a specific hormone.

• Major organs in the endocrine system: Hypothalamus, pituitary, thyroid, parathyroid, adrenal, pancreas, ovaries, testes.

• Exocrine vs. endocrine glands: Exocrine glands secrete through ducts; endocrine glands release hormones into the bloodstream.

• Endocrine vs. nervous system: Endocrine is slower, using hormones; nervous system is fast, using electrical signals.

• Hypothalamus communication: It communicates with the pituitary gland via releasing and inhibiting hormones.

• Tropic/tropin hormone meaning: It stimulates another gland to release hormones.

• Importance of growth hormone: Essential for childhood growth; declines with age.

• Thyroid necessity: Iodine is needed to produce thyroid hormones.

• Adrenal medulla difference: It releases epinephrine and norepinephrine directly into the blood like the nervous system.

• Three adrenal cortex zones and hormones:

  • Zona glomerulosa: Aldosterone

  • Zona fasciculata: Cortisol

  • Zona reticularis: Androgens

• Stress hormone: Cortisol.

• Paired glands: Adrenal glands, gonads (ovaries/testes).

• Main pancreas tissue: Exocrine tissue (acini cells).

• Hyperglycemic vs. hypoglycemic: High vs. low blood sugar.

• Hormones for growth and development: GH, thyroid hormones, insulin, sex hormones.

• Disorders from hormone imbalance:

  • Hypersecretion of GH: Gigantism (childhood), acromegaly (adulthood).

  • Hyposecretion of ADH: Diabetes insipidus.

• Thyroid disorders and causes:

  • Hypothyroidism: Iodine deficiency, Hashimoto’s disease.

  • Hyperthyroidism: Graves’ disease, tumors.

• Excess PTH secretion: Causes hypercalcemia and bone loss.

• Cushing syndrome: Excess cortisol, causing weight gain, high blood pressure.

• Diabetes mellitus: High blood sugar due to insulin issues; Type 2 is most common.

Blood & Circulatory System:

• Blood’s role in homeostasis: Transports gases, nutrients, hormones, and regulates temperature.

• Functions of circulatory system: Transport, protection, regulation.

• Two blood components: Plasma and formed elements.

• Three plasma proteins: Albumin, globulins, fibrinogen.

• Formed elements: RBCs, WBCs, platelets.

• Hematocrit value: Percentage of RBCs in blood; affected by hydration, disease.

• Two blood properties: Viscosity (thickness) and osmolarity (solute concentration).

• Erythrocyte survival importance: Oxygen transport.

• Why RBCs in humans? More efficient oxygen transport.

• How RBCs carry oxygen: Hemoglobin binds oxygen.

• Why RBCs don’t consume oxygen: Lack mitochondria.

• Formed element production names:

  • Hematopoiesis: All formed elements.

  • Erythropoiesis: RBCs.

  • Leukopoiesis: WBCs.

• Similar RBC, WBC, platelet production: All originate from hematopoietic stem cells.

• Hormone for RBC production: Erythropoietin (EPO), from kidneys.

• RBC homeostasis trigger: Low oxygen → kidney releases EPO → more RBCs.

• Factors increasing EPO: Hypoxia, blood loss, high altitude.

• Sickle cell disease: Genetic RBC disorder; persists due to malaria resistance.

• Antigen vs. antibody: Antigens are markers; antibodies attack foreign antigens. In blood, antigens determine type, antibodies attack mismatched blood.

• One antibody action: Agglutination (clumping foreign cells).

• Blood type antigens/antibodies:

  • A: A antigen, anti-B antibody

  • B: B antigen, anti-A antibody

  • AB: A & B antigens, no antibodies

  • O: No antigens, anti-A & anti-B antibodies

• Blood type inheritance: Determined by parents' ABO genes.

• Rh group: Presence (Rh+) or absence (Rh-) of Rh antigen.

• Importance of Rh- status: Can cause issues in pregnancy if mother is Rh- and baby is Rh+.

• Hemolytic disease of newborn: Mother’s antibodies attack Rh+ fetal blood.

• Few WBCs in blood: They mostly reside in tissues.

• Leukocyte function: Immunity and defense.

• WBC types & functions:

  • Neutrophils: Bacteria killers.

  • Lymphocytes: Adaptive immunity.

  • Monocytes: Macrophage precursors.

  • Eosinophils: Fight parasites, allergies.

  • Basophils: Release histamine, heparin.

• Causes of WBC increase: Infections, inflammation.

• Most/least abundant WBCs: Neutrophils (most), basophils (least).

• Histamine & heparin: Histamine dilates vessels; heparin prevents clotting.

• Why count RBCs? Diagnose anemia, oxygen capacity.

• Leucopenia vs. leukocytosis: Low vs. high WBC count.

• Leukemia and types: Blood cancer; acute and chronic.

• Why leukemia is harmful: Excess WBCs disrupt normal blood function.

Platelets & Clotting:

• Platelets & origin: Cell fragments from megakaryocytes.

• Hemostasis: Blood clotting process.

• Formed element for hemostasis: Platelets.

• Most immediate hemostasis step: Vascular spasm.

• Most effective hemostasis step: Coagulation.

• Extrinsic vs. intrinsic coagulation: Extrinsic triggered by external damage; intrinsic by internal vessel damage.

• Shared coagulation pathway: Both lead to fibrin formation.

• Beginning clotting factors:

  • Extrinsic: Factor III (tissue factor).

  • Intrinsic: Factor XII.

  • Common pathway: Factor X activation.

• Fibrinolysis: Breakdown of clots via plasmin.

• Prevention of clot formation: Anticoagulants like heparin, plasmin.

• Anemia: Low RBCs or hemoglobin.

• Hemophilia: Inherited clotting disorder.

• Thrombosis: Clot in an unbroken vessel.

• Embolism: Moving clot blocking blood flow.