Anatomy and Physiology II Lesson: Blood, Organs & Body Systems

Lesson Overview

• Blood Physiology: Structure, Composition, and Regulation
• Cardiovascular System: Circulation, Valves, and Regulation
• Respiratory System: Airflow and Control
• Immune and Lymphatic Systems
• Digestive System: Breakdown and Absorption
• Endocrine System: Hormonal Signaling and Homeostasis
• Urinary System: Filtration, Reabsorption, and Regulation
• Blood Formation and Stem Cells
• Blood Pressure and Clinical Indicators
• Conclusion

When students can name organs but struggle to explain how systems interact, it shows a need for deeper insight into Anatomy and Physiology II. This lesson provides a complete view of how blood, hormones, organs, and regulation work together-bridging gaps between theory and the integrated function of the human body.

Blood Physiology: Structure, Composition, and Regulation

A. Blood pH and Homeostasis

Blood has a tightly regulated pH range of 7.35 to 7.45, which is slightly alkaline. Even slight deviations can affect enzyme function and organ performance. The body uses buffer systems, respiratory control, and renal regulation to maintain this balance.

B. Plasma: The Fluid Matrix

Plasma makes up about 55% of total blood volume and is about 90% water. It contains:

• Plasma proteins: Albumin (osmotic balance), Globulins (immunity), Fibrinogen (clotting)
• Electrolytes: Sodium, potassium, calcium, chloride, bicarbonate
• Nutrients: Glucose, amino acids, vitamins
• Hormones
• Wastes: Urea, creatinine, bilirubin

C. Formed Elements

• Red Blood Cells (RBCs): Contain hemoglobin to carry oxygen; lifespan ~120 days
• White Blood Cells (WBCs): Include lymphocytes, monocytes, neutrophils, eosinophils, basophils
• Platelets: Cell fragments involved in clotting

D. Blood Typing and Transfusion

• Type O blood: Lacks A and B antigens-universal donor
• Type AB blood: No anti-A or anti-B antibodies-universal recipient
• The Rh factor (+ or −) also affects compatibility

Cardiovascular System: Circulation, Valves, and Regulation

A. Vessel Classification

• Elastic arteries: Closest to the heart; absorb pressure (e.g., aorta)
• Muscular arteries: Distribute blood to body regions
• Arterioles: Feed directly into capillary beds
• Venules and veins: Return blood to the heart

B. Heart Valves and Function

• The tricuspid valve prevents backflow from the right ventricle to the right atrium
• It closes during systole, when the ventricle contracts

C. Hemodynamics and Shock

A large blood loss, such as hemorrhage, leads to:

• Decreased blood volume → decreased venous return
• Reduced cardiac output
• Ultimately, lower blood pressure

The body compensates via vasoconstriction, increased heart rate, and hormonal release (e.g., ADH, aldosterone).

D. Specialized Circulation: Hepatic Portal System

• Blood from the digestive tract flows to the liver via the hepatic portal vein
• The liver processes nutrients and detoxifies before blood enters systemic circulation

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Cardiovascular System Quiz Exam: Trivia!

Respiratory System: Airflow and Control

A. Airway Patency and Structure

The trachea remains open due to C-shaped cartilage rings, which prevent collapse during inhalation and exhalation. Its inner lining is made of pseudostratified ciliated epithelium, which traps particles and moves mucus upward.

B. Respiratory Regulation

Respiratory centers are in the medulla oblongata and pons:

• Medulla controls the basic rhythm of breathing
• Pons smoothens the transition between inhalation and exhalation

These centers respond to CO₂ levels, pH, and oxygen concentration.

Immune and Lymphatic Systems

A. Lymph Composition and Movement

• Lymph is interstitial fluid drained from tissues
• Contains water, ions, proteins, but not red blood cells
• Travels through lymphatic vessels and is filtered in lymph nodes

B. Lymph Node Function

• Afferent lymphatic vessels bring lymph into the node
• Efferent vessels carry it out
• Nodes contain B cells, T cells, macrophages for defense

C. Peyer's Patches

• Found in the distal small intestine (ileum)
• Contain lymphocytes that monitor and respond to intestinal pathogens

D. T Cells and Immunity

• Helper T cells: Activate other immune cells
• Cytotoxic T cells: Directly destroy infected or abnormal cells
• Regulatory T cells: Suppress overactive responses
• Antigenic is not a T cell type; it's a term describing molecules that trigger immunity

E. Inflammation Response

• Triggered by injury or infection
• Vasodilation increases blood flow (hyperemia), causing redness and heat
• WBCs are recruited to fight pathogens and begin healing

Digestive System: Breakdown and Absorption

A. Digestion

• Includes mechanical (chewing, churning) and chemical (enzymes, acids) processes
• Bile, produced by the liver and stored in the gallbladder, is released into the duodenum to emulsify fats

B. Gastric Defense Mechanisms

The stomach mucosal barrier includes:

• Tight junctions between cells
• Bicarbonate-rich mucus
• Rapid cell renewal

Rennin, an enzyme involved in milk digestion in infants, is not part of this barrier.

C. Vitamin Absorption

Vitamin B12 absorption depends on intrinsic factor, a glycoprotein secreted by parietal cells in the stomach. Without it, B12 cannot be absorbed in the ileum, leading to anemia.

Endocrine System: Hormonal Signaling and Homeostasis

A. Second Messenger System

Many hormones bind to cell membrane receptors and activate G proteins, which then produce cyclic AMP (cAMP)-a second messenger that triggers changes inside the cell.

This is common for non-steroid hormones like epinephrine and glucagon.

B. Metabolic Regulation

• Hormones help regulate blood sugar, basal metabolic rate, electrolyte balance, and growth
• Growth hormone (GH) targets bones and skeletal muscles
• Thyroid hormones and insulin are essential for metabolism

Urinary System: Filtration, Reabsorption, and Regulation

A. Nephron Function

The nephron is the functional unit of the kidney. Processes include:

• Filtration: In glomerulus
• Reabsorption: Water, nutrients, and ions are reclaimed
• Secretion: Wastes added to filtrate

B. Juxtaglomerular Apparatus (JGA)

Located near the glomerulus, the JGA:

• Monitors blood pressure and filtrate volume
• Releases renin, activating the RAAS pathway to raise blood pressure

C. Water Reabsorption

Driven by osmosis, especially in response to ADH (antidiuretic hormone)

• ADH increases water reabsorption in the collecting ducts
• Alcohol suppresses ADH, causing diuresis (increased urination)

Blood Formation and Stem Cells

A. Hematopoiesis

All blood cells originate from pluripotent stem cells (hemocytoblasts) in red bone marrow.

These stem cells differentiate into:

• RBCs (oxygen transport)
• WBCs (immunity)
• Platelets (clotting)

Proper function of bone marrow ensures the continuous renewal of these vital components.

Blood Pressure and Clinical Indicators

A. Hypertension

Defined as a blood pressure reading consistently at or above 130/80 mmHg. For example:

• 170/96 in a 50-year-old = high blood pressure
• Can lead to heart disease, kidney failure, and stroke

Monitoring and managing blood pressure is essential to prevent long-term complications.

Conclusion

Anatomy and Physiology II integrates knowledge across systems, highlighting how blood transports oxygen and nutrients, how the immune system identifies threats, how kidneys regulate balance, and how the digestive and endocrine systems support survival. Understanding these connections enables students to comprehend the human body as an intricate and coordinated living system.

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Anatomy and Physiology II