Cardiovascular System, Blood, and Lymphatic System: Structure, Function, and Development

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Cardiovascular System, Blood, and Lymphatic System

Overview

This study guide covers the anatomy and physiology of the cardiovascular system, blood, and lymphatic system, including the development of lymphatic structures. It is designed for college-level Anatomy & Physiology students and integrates clinical case studies, cellular composition, and organ function.

Blood: Structure and Function

Composition of Whole Blood

Plasma (55-62%): Fluid matrix containing water, proteins, nutrients, hormones, and waste products.
Formed Elements (38-45%): Cellular components including erythrocytes (RBCs), leukocytes (WBCs), and platelets.

Plasma Proteins

Albumin: Maintains osmotic pressure, transports substances.
Globulins: Transport proteins, antibodies (immunoglobulins).
Fibrinogen: Essential for blood clotting.

Other Solutes

Electrolytes, nutrients, gases, waste products.

Formed (Cellular) Elements

Red Blood Cells (Erythrocytes): Transport oxygen and carbon dioxide.
White Blood Cells (Leukocytes): Immune defense; include neutrophils, eosinophils, basophils, lymphocytes, and monocytes.
Platelets (Thrombocytes): Cell fragments involved in clotting.

Complete Blood Count (CBC)

CBC is a diagnostic test measuring the concentration of blood components.

Parameter	Males	Females
Hematocrit	48-54%	37-47%
Hemoglobin (g/dL)	14-17	12-16
RBC count (x106/μL)	4.5-5.9	3.8-5.2
WBC count (x103/μL)	4.1-11	4.1-11
Platelets (x103/μL)	150-450	150-450

Case Study: Hanna S.

Symptoms: Fatigue, irritability, light-headedness.
History: Ulcerative colitis, recent dietary changes (vegan, low iron intake).
CBC Results: Hematocrit 32%, Hemoglobin 10 g/dL, WBC 5.3 x 103/μL, Platelets 200 x 103/μL, Ferritin low, MCV 74 fL (microcytic anemia).

Erythrocytes (Red Blood Cells)

Structure and Function

Biconcave disc shape increases surface area for gas exchange.
Lack nucleus and mitochondria; rely on anaerobic metabolism.
Lifespan: ~120 days; produced in red bone marrow.

Erythropoiesis

Regulated by erythropoietin (EPO) from kidneys.
Triggered by low oxygen levels (hypoxia); HIF1α stabilizes and induces EPO gene transcription.
Requires iron, vitamin B12, and folate.

Types of Anemia

Iron-deficiency anemia: Low iron, microcytic RBCs.
Pernicious anemia: Vitamin B12 deficiency.
Hemolytic anemia: RBC destruction.
Sickle cell anemia: Abnormal hemoglobin structure.

Hemoglobin (Hb)

Protein in RBCs responsible for oxygen transport.
Consists of four polypeptide subunits (2 alpha, 2 beta in adults).
Each subunit contains a heme group with iron (Fe2+).
Iron binds oxygen; polypeptide units bind carbon dioxide.

Blood Types and Antigens

ABO Blood Group System

Blood cells have genetically determined antigens (A, B, AB, O) on their surface.
Plasma contains antibodies against antigens not present on RBCs.
Agglutination occurs when antibodies bind to antigens, causing clumping.

Type	Surface Antigen	Plasma Antibody
A	A	Anti-B
B	B	Anti-A
AB	A & B	None
O	None	Anti-A & Anti-B

Rhesus (Rh) Factor

Rh+ has D antigen; Rh- lacks D antigen.
Rh- individuals can develop anti-D antibodies after exposure to Rh+ blood.
Hemolytic disease of the newborn can occur if Rh- mother carries Rh+ fetus.

Hematopoietic Stem Cells and Bone Marrow

Hematopoietic Stem Cells

Multipotent cells in bone marrow give rise to all blood cell types.
Differentiate into myeloid (RBCs, platelets, granulocytes, monocytes) and lymphoid (B cells, T cells, NK cells) lineages.

Bone Marrow & Hematopoiesis

Site of blood cell production.
Contains stem cells, reticular cells, macrophages, and adipocytes.

Leukocytes (White Blood Cells)

Classification

Agranular: Lymphocytes (B, T, NK cells), Monocytes.
Granular: Neutrophils, Eosinophils, Basophils.

Functions

Immune defense against pathogens.
Phagocytosis, antibody production, inflammation.

Platelets & Hemostasis

Platelets

Fragments of megakaryocytes; initiate clotting.
Form platelet plug at injury site.
Contain enzymes and chemicals for clot formation.

Hemostasis

Process that stops blood loss from damaged vessels.
Thrombocytopenia: Low platelet count, risk of bleeding.

Lymphatic System

Lymphocytes & Immune Response

Cell-mediated immunity: T cells attack pathogens directly.
Antibody-mediated immunity: B cells produce antibodies to neutralize pathogens.
Memory cells provide long-term immunity.

Lymphocyte Formation and Maturation

Originates in red bone marrow.
B cells mature in bone marrow; T cells migrate to thymus for maturation.

Lymphatic Tissues

Tissues dominated by lymphocytes, loosely aggregated in connective tissue.
Lymphatic nodules have germinal centers with proliferating lymphocytes.
Examples: Tonsils, Peyer's patches, appendix.

Development of the Lymphatic System

Embryonic development involves formation of lymph sacs and ducts.
Thymus develops from third pharyngeal pouch.

Tonsils

Type of mucosa-associated lymphoid tissue (MALT).
Five types: single pharyngeal (adenoid), paired palatine, paired lingual.

Thymus

Located posterior to sternum; largest in children.
Consists of cortex (immature T cells) and medulla (mature T cells).
Produces thymosin for T cell maturation.

Lymph Nodes

Filter lymph; contain B cells, T cells, macrophages, dendritic cells.
Located in cortex, paracortex, and medulla.

Distribution of Lymph Nodes

Cervical: Head and neck
Axillary: Armpit
Popliteal: Legs
Inguinal: Groin
Thoracic: Lungs, respiratory tract
Abdominal: Digestive, urinary, reproductive organs

Lymphatic Vessels

Capillaries larger and more permeable than blood capillaries.
Anchoring filaments keep capillaries open.
Lymph is fluid from interstitial space containing proteins, pathogens, and leukocytes.

Lymph Flow

Low pressure system; valves prevent backflow.
Skeletal muscle contraction propels lymph.

Leg Edema

Edema: Swelling from fluid buildup.
Pitting edema: Indentation remains after pressing; often due to venous insufficiency.
Non-pitting edema: No indentation; often due to lymphatic drainage issues (e.g., lymphedema).

Thoracic Duct

Main lymphatic vessel; empties into left subclavian vein.
Collects lymph from left side of body below diaphragm.
Right lymphatic duct drains right upper quadrant.

Spleen

Largest lymphatic organ; located in left upper abdomen.
Filters blood, removes old erythrocytes, stores platelets.
Consists of diaphragmatic and visceral surfaces.

Red & White Pulp of Spleen

Red pulp: Contains erythrocytes and macrophages.
White pulp: Contains T and B lymphocytes, macrophages.

Recall: Artery vs. Vein

Arteries have thicker walls, more smooth muscle, and elastic fibers.
Veins have thinner walls, larger lumen, and valves to prevent backflow.

Key Equations

Hematocrit Calculation:
Mean Corpuscular Volume (MCV):

Summary Table: Blood Group Distribution

Population	O	A	B	AB	Rh+
United States	45	41	10	4	85
Black American	49	27	20	4	92
Caucasian	45	40	11	4	85
Asian American	43	27	25	5	99

Additional info: Table values inferred from provided slide and standard references.