BIO211 Study Guide: Endocrine, Blood, Lymphatic, and Immune Systems

Endocrine System

Definition and Types of Hormones

The endocrine system regulates body functions through the release of hormones, which are chemical messengers secreted by glands and transported via the bloodstream to target organs.

• Hormone: A molecule released by endocrine glands that affects distant target cells.

• Types:

  • Bound hormones: Attached to carrier proteins in blood, increasing their stability and half-life.

  • Free hormones: Not bound, act quickly but are removed rapidly.

  • Second messengers: Hormones (often peptide or protein) that act via intracellular signaling molecules (e.g., cAMP).

• Importance: Hormones regulate metabolism, growth, reproduction, and homeostasis.

Hormone Interactions

• Synergism: Two hormones amplify each other's effects.

• Antagonism: One hormone opposes the action of another.

• Permissiveness: One hormone enables another to act.

Endocrine Glands and Hormones

Each hormone is produced by a specific gland, acts on target tissues, and is released in response to particular stimuli. Disorders may arise from hypo- or hypersecretion.

• ADH (Antidiuretic Hormone): Produced by hypothalamus, released by posterior pituitary; targets kidneys; increases water reabsorption; deficiency causes diabetes insipidus.

• Oxytocin: Posterior pituitary; targets uterus and mammary glands; stimulates contractions and milk ejection.

• ANP (Atrial Natriuretic Peptide): Heart; targets kidneys; reduces blood volume and pressure.

• FSH (Follicle Stimulating Hormone): Anterior pituitary; targets gonads; stimulates gamete production.

• GH (Growth Hormone): Anterior pituitary; targets most tissues; stimulates growth; excess causes gigantism/acromegaly, deficiency causes dwarfism.

• Thyroxine (T4) & Triiodothyronine (T3): Thyroid; regulate metabolism; deficiency causes hypothyroidism, excess causes hyperthyroidism.

• Cortisol: Adrenal cortex; stress response; excess causes Cushing's syndrome.

• Aldosterone: Adrenal cortex; regulates sodium and potassium.

• LH (Luteinizing Hormone): Anterior pituitary; triggers ovulation/testosterone production.

• Thymopoietin: Thymus; involved in T cell maturation.

• ACTH (Adrenocorticotropic Hormone): Anterior pituitary; stimulates adrenal cortex.

• Insulin: Pancreas; lowers blood glucose; deficiency causes diabetes mellitus.

• TSH (Thyroid Stimulating Hormone): Anterior pituitary; stimulates thyroid.

• Epinephrine & Norepinephrine: Adrenal medulla; fight-or-flight response.

• Erythropoietin: Kidneys; stimulates RBC production.

• PTH (Parathyroid Hormone): Parathyroid; increases blood calcium.

• Glucagon: Pancreas; raises blood glucose.

• Calcitonin: Thyroid; lowers blood calcium.

• Melatonin: Pineal gland; regulates sleep.

• Prolactin: Anterior pituitary; stimulates milk production.

• Androgens: Adrenal cortex/gonads; male sex hormones.

• Progesterone & Testosterone: Gonads; regulate reproductive functions.

• Serotonin: CNS; mood regulation.

• Leptin: Adipose tissue; regulates appetite.

Up-Regulation vs. Down-Regulation

• Up-Regulation: Increase in receptor number in response to low hormone levels.

• Down-Regulation: Decrease in receptor number due to high hormone levels.

Anterior vs. Posterior Pituitary

• Anterior Pituitary: Produces and releases hormones via the hypophyseal portal system.

• Posterior Pituitary: Stores and releases hormones made in the hypothalamus; uses neural tract.

• Tract: Neural connection.

• Portal System: Blood vessel network connecting hypothalamus and anterior pituitary.

Tropins

• Tropin: Hormone that stimulates another endocrine gland (e.g., TSH, ACTH).

Adrenal Cortex Zones

• Zona Glomerulosa: Produces mineralocorticoids (aldosterone).

• Zona Fasciculata: Produces glucocorticoids (cortisol).

• Zona Reticularis: Produces androgens.

Blood

Composition and Percentages

• Blood: Connective tissue composed of plasma (55%) and formed elements (45%).

• Formed elements: Erythrocytes (RBCs), leukocytes (WBCs), platelets.

Hematocrit

• Hematocrit: Percentage of RBCs in blood; average is 45%.

Amount, pH, and Functions

• Volume: 4-6 liters in adults.

• pH: 7.35-7.45.

• Functions: Transport, regulation, protection.

Viscosity and Osmolarity

• Viscosity: Resistance to flow; mainly due to RBCs.

• Osmolarity: Solute concentration; mainly due to plasma proteins.

Albumin

• Albumin: Most abundant plasma protein; maintains osmotic pressure.

Hemoglobin Structure and Function

• Structure: Four globin chains, each with a heme group.

• Function: Transports oxygen and carbon dioxide.

Formed Elements and Functions

• Erythrocytes: Transport oxygen.

• Leukocytes: Defend against infection.

• Platelets: Blood clotting.

Serum vs. Plasma

• Plasma: Liquid part of blood with clotting factors.

• Serum: Plasma without clotting factors.

Blood Cell Formation (Hematopoiesis)

• Location: Red bone marrow.

• Factors: Erythropoietin, iron, vitamin B12, folic acid.

Fate of Erythrocytes

• RBCs live ~120 days; destroyed in spleen/liver; components recycled.

Anemia Types

• Iron-deficiency: Low iron.

• Pernicious: Low vitamin B12.

• Hemolytic: RBC destruction.

• Aplastic: Bone marrow failure.

Other Blood Disorders

• Polycythemia: Excess RBCs.

• Leukemia: Cancer of WBCs.

• Thalassemia: Genetic hemoglobin disorder.

• Sickle Cell: Abnormal hemoglobin.

Leukocytes: Types and Abundance

Leukocyte	Type	Function	Relative Abundance
Neutrophil	Granulocyte	Phagocytosis	Most abundant
Lymphocyte	Agranulocyte	Immune response	2nd
Monocyte	Agranulocyte	Phagocytosis	3rd
Eosinophil	Granulocyte	Parasitic defense	4th
Basophil	Granulocyte	Histamine release	Least abundant

Platelets

• Derived from megakaryocytes in bone marrow.

Hemostasis Phases

• Vascular spasm

• Platelet plug formation

• Coagulation

Thrombus, Embolus, Embolism

• Thrombus: Clot in unbroken vessel.

• Embolus: Traveling clot.

• Embolism: Embolus lodged in vessel.

Thrombin and Fibrinogen in Coagulation

• Thrombin converts fibrinogen to fibrin, forming clot.

Blood Types and Transfusions

Blood Type	Can Receive From	Can Donate To
A	A, O	A, AB
B	B, O	B, AB
AB	A, B, AB, O	AB
O	O	A, B, AB, O

Rh Type and Pregnancy

• Rh incompatibility can cause hemolytic disease of the newborn (erythroblastosis fetalis).

Erythroblastosis Fetalis

• Occurs when Rh-negative mother has Rh-positive fetus; maternal antibodies attack fetal RBCs.

Agglutinate

• Clumping of cells due to antibody-antigen reaction.

Lymphatic System

Functions

• Fluid balance, immune defense, fat absorption.

Cells, Tissues, Organs

• Cells: Lymphocytes, macrophages.

• Tissues: Lymphoid tissue (diffuse, nodules).

• Organs: Lymph nodes, spleen, thymus, tonsils.

Lacteals

• Specialized lymphatic capillaries in intestines; absorb dietary fats.

Three Tunics of Lymphatic Vessels

• Intima: Inner layer.

• Media: Smooth muscle.

• Adventitia: Outer connective tissue.

Lymph Transport and Blockage

• Transported by skeletal muscle, valves, respiratory movements.

• Blockage causes edema (swelling).

Lymphoid Tissue Types

• Diffuse lymphoid tissue, lymphoid follicles/nodules.

Lymph Node and Tonsil Structure

• Lymph nodes: Cortex (follicles), medulla.

• Tonsils: Pharyngeal, palatine, lingual; located in throat.

Swollen vs. Sore Lymph Nodes

• Swollen: Increased activity.

• Sore: Infection/inflammation.

Immune System

Innate vs. Adaptive Defenses

Innate (Nonspecific)	Adaptive (Specific)
Physical barriers, phagocytes, inflammation	Lymphocytes, antibodies
Immediate response	Delayed, memory

Cells Associated with Defenses

• Innate: Neutrophils, macrophages, NK cells.

• Adaptive: B cells, T cells.

Inflammatory Response

• Redness, heat, swelling, pain; increases blood flow and immune cell recruitment.

Key Terms

• Interferon: Antiviral protein.

• Complement: Plasma proteins aiding immunity.

• Antigen: Substance provoking immune response.

• Hapten: Small molecule, immunogenic when attached to carrier.

Passive vs. Active Immunity

• Active: Exposure to antigen; memory develops.

• Passive: Antibodies transferred; no memory.

Antibody Action and Epitopes

• Antibodies neutralize, agglutinate, precipitate, and activate complement.

• Epitope: Antigenic determinant.

MHC Molecules

• Major histocompatibility complex; presents antigens to T cells.

T Cells and HIV

• HIV infects helper T cells, impairing immunity.

Hypersensitivities

• Type I: Immediate (allergy).

• Type II: Cytotoxic.

• Type III: Immune complex.

• Type IV: Delayed.

Anaphylactic Shock

• Severe allergic reaction; rapid vasodilation and airway constriction.

Additional info: Academic context and examples were added to clarify brief points and ensure completeness.