Chapter 16: The Cardiovascular System

• Definition: The circulatory system is a closed system of vessels responsible for transporting blood to all cells and tissues in the body.

• Components:

  • Heart: Pumps blood through the circulatory system.

  • Blood Vessels: Includes arteries, veins, and capillaries that carry blood to and from the heart.

  • Lymph Vessels: Part of the immune system that transports lymph.

Functions of the Circulatory System:

1. Transport Functions:

   • Trophic: Nutrient delivery.

   • Respiratory: Oxygen transport to cells, carbon dioxide removal.

   • Excretory: Waste product removal.

2. Integration: Coordination of body functions.

3. Regulation: Maintaining homeostasis (e.g., temperature, pH).

4. Participation in Immune Reactions: Facilitates immune responses.

Development of the Cardiovascular System:

• Primary Angiogenesis: Formation of vessels from mesenchyme in the yolk sac during the 3rd week of embryonic development.

• Secondary Angiogenesis: Formation of new vessels from existing ones during the embryonic and post-embryonic periods.

• Heart Development: Formed from mesenchymal tubes and myoepicardial plate (visceral splanchnotom).

Structure of the Heart:

• Consists of three coats:

  • Endocardium: Inner layer resembling blood vessel structure; has four layers (endothelial, subendothelial, muscular-elastic, and external connective). It forms heart valves.

  • Myocardium: Main heart muscle layer, consists of cardiac muscle tissue (parenchyma) and connective tissue (stroma). Contains three types of cardiomyocytes:

    • Working/Contractive Cardiomyocytes: Responsible for heart contractions.

    • Conductive Cardiomyocytes: Involved in impulse conduction (e.g., pacemaker cells in the S-A node).

    • Secretory Cardiomyocytes: Produce hormones like Na-uretic factor, regulate sodium excretion.

  • Epicardium: Outermost layer composed of visceral pericardium, with two layers (internal connective tissue and external mesothelium).

Innervation and Blood Supply:

• Sympathetic Innervation: Involves preganglionic neurons (Th1-Th5) and postganglionic neurons (located in stellate ganglia).

• Parasympathetic Innervation: Involves vagus nerve, with postganglionic neurons in intramural ganglia of the heart.

Age-Related Changes:

• Elderly Heart Features:

  1. Myocardium becomes flabby.

  2. Nuclear/cytoplasmic ratio decreases.

  3. Basement membrane widens.

  4. Development of cardiosclerosis (fibrous tissue growth).

• Regeneration: Limited to cellular hypertrophy/hyperplasia; significant changes on the intracellular level.

Blood Vessels:

• Coats of Vessels: Include internal (endothelium), middle (muscular), and external (adventitial) layers.

• Types of Blood Vessels:

  1. Arteries: Carry blood away from the heart (Three Types):

     • Elastic Arteries (e.g., aorta): Significant elastic fibers allow expansion during heart contractions.

     • Muscular Arteries: Regulate blood flow using smooth muscle contraction.

     • Mixed Arteries: Intermediate features between elastic and muscular arteries.

  2. Veins: Carry blood toward the heart (Two Types):

     • Muscular Veins: Contain smooth muscle and have valves.

     • No-Muscular Veins: Less muscular structure, does not regulate blood flow.

• Microcirculatory Vessels: Include arterioles, capillaries, and venules, facilitating nutrient and gas exchange.

Microcirculatory Net Functions:

1. Nutrition and Respiration

2. Blood Storage

3. Drainage

4. Regulation of Blood Flow

5. Transportation

Capillary Structure:

• Capillaries: Thin-walled vessels allowing for easy exchange of oxygen, nutrients, and waste between blood and tissues. Three Types:

  1. Somatic (Continuous): Found in muscles and brain.

  2. Visceral (Fenestrated): Found in internal organs.

  3. Sinusoidal: Found in liver and spleen, allowing large molecules to pass.

Lymphatic Vessels:

• Function: Drain excess interstitial fluid and transport immune cells.

• Structure: Similar to veins, with thinner walls and valves to prevent backflow.

Chapter 18: The Respiratory System

• Functions:

  • External Respiration: Gas exchange between air and blood.

  • Airway Conducting: Includes nasal cavities, pharynx, larynx, trachea.

Embryonic Development of the Lungs:

1. Glandular Stage (5th Week to 4th Month): Formation of bronchial tree.

2. Canalicular Stage (4th Month to 6th Month): Formation of respiratory bronchioles, increase in capillary network.

3. Alveolar Stage (6th Month to Birth): Formation of alveolar sacs, until the first breath.

Chapter 20: The Endocrine System

• Definition: Comprises glands and cells that secrete hormones directly into the blood.

• Major Functions: Hormones regulate metabolism, growth, development, and reproduction.

• Hormones can be categorized into four types based on chemical structure:

  1. Amino acid derivatives

  2. Small peptides

  3. Proteins

  4. Steroids

Hypophysis Cerebri (Pituitary Gland):

• Location: Suspended from the floor of the third ventricle, lies in a depression on the sphenoid bone.

• Subdivisions: Anterior (adenohypophysis), Intermediate, and Posterior (neurohypophysis).

• Function: Produces various hormones influencing other endocrine glands, including growth hormone (GH), thyroid stimulating hormone (TSH), etc.

Summary of Selected Endocrine Organs:

1. Adrenal Glands: Produce mineralocorticoids (aldosterone) and glucocorticoids (cortisol).

2. Thyroid Gland: Produces T3 and T4 hormones, important for metabolism regulation.

3. Pancreas: Endocrine function includes insulin production for glucose metabolism.

Chapter 22: The Digestive System

• Overview: Involves organs that process food from ingestion to digestion and absorption.

Small Intestine Functions:

1. Digestive Function: Digestion of nutrients.

2. Absorptive Function: Absorption of digested nutrients.

3. Motor-Evacuation Function: Movement of contents through the digestive tract.

Structure of the Small Intestine:

• Layers: Mucosa, submucosa, muscularis, and serosa.

• Features: Villi (projections for absorption), crypts (invaginations that secrete intestinal juices), and circular folds (increased surface area).

• Cell Types: Enterocytes (absorptive cells), goblet cells (mucus secretion), Paneth cells (secretion of antimicrobial enzymes), and endocrine cells (producing digestive hormones).

These notes provide a comprehensive overview of the cardiovascular and respiratory systems, as well as the endocrine and digestive systems, highlighting the important structures, functions, and developmental aspects.