Anatomy

Full Answer Section

• The Respiratory System: Regulates blood pH by influencing carbonic acid levels through CO2 removal.
  • Increased ventilation expels CO2, the respiratory acid, from the blood. This lowers H2CO3 levels and raises blood pH (more alkaline).
  • Conversely, decreased ventilation retains CO2, leading to higher H2CO3 levels and a more acidic blood pH.

2. Protecting the Stomach from Self-Digestion:

• The stomach lining is constantly exposed to powerful digestive enzymes like pepsin. Several mechanisms prevent self-destruction:
  • Mucus Layer: A thick layer of mucus produced by the stomach lining acts as a barrier, separating the enzymes from the stomach wall.
  • Epithelial Cell Renewal: Stomach lining cells are constantly replaced, ensuring a fresh barrier against enzymes.
  • Bicarbonate Secretion: The stomach lining secretes bicarbonate to neutralize excess acid and create a slightly alkaline environment that is less hospitable to enzyme activity.
  • Tight Junctions: Tight junctions between stomach epithelial cells prevent enzymes from leaking into deeper tissues.

3. Conducting vs. Respiratory Zones of the Lungs:

4. Impact of Alveolar Damage from Smoking:

Smoking damages the delicate structures of the alveoli, leading to several consequences that impair gas exchange:

• Reduced Surface Area: Damaged alveoli lose their sac-like structure, reducing the available surface area for gas diffusion.
• Thickened Walls: Inflammation and scarring can thicken alveolar walls, hindering the diffusion of oxygen and carbon dioxide.
• Loss of Elasticity: Damaged alveoli lose their ability to expand and contract efficiently, compromising ventilation.

These factors together lead to hypoxia (low blood oxygen) and hypercapnia (high blood carbon dioxide), disrupting vital cellular functions and potentially causing respiratory failure.

5. Enteric Nervous System and Digestion:

• The Enteric Nervous System (ENS): An intricate network of nerves embedded within the digestive tract walls. It regulates various digestive functions like:
  • Muscle contractions: Controls the movement of food through the digestive tract by coordinating smooth muscle contractions (peristalsis).
  • Secretion of digestive juices: Regulates the release of enzymes, hormones, and mucus necessary for digestion and absorption.
  • Blood flow: Adjusts blood flow to different digestive organs based on their needs.

Autonomic Nervous System (ANS) and Digestive Issues:

• The ANS (sympathetic and parasympathetic) can influence digestion, but excessive or imbalanced activity can lead to problems:
  • Stress: Chronic stress can trigger the sympathetic nervous system, which can inhibit digestive processes and lead to constipation or diarrhea.
  • Certain Medications: Medications that affect the ANS can cause digestive side effects like nausea, vomiting, or constipation.
  • Neurological Disorders: Diseases affecting the nervous system can disrupt communication with the digestive tract, leading to digestive problems.

By understanding these interactions, we can appreciate the delicate balance required for proper digestion and the potential consequences of disruptions.

Sample Answer

Balancing Acts: Bicarbonate, Gas Exchange, and Protection

1. Bicarbonate Conservation and Blood pH:

• The Kidneys: The renal system plays a crucial role in maintaining blood pH by conserving bicarbonate ions (HCO3-).
  • Most filtered bicarbonate from the blood is reabsorbed in the proximal tubules through a complex process involving carbonic anhydrase and sodium-hydrogen exchange.
  • This reabsorption keeps HCO3- levels in the blood stable, which is essential for buffering carbonic acid (H2CO3) and maintaining blood pH within a normal range.