Respiration and Digestion: Processes and Functions

Respiration

Respiration is a process divided into two processes:

  • External respiration is the gas exchange between the lungs and the atmosphere, where oxygen enters the lungs and carbon dioxide exits. It does not create ATP molecules.
  • Internal respiration is the gas exchange between the bloodstream and the tissues, where oxygen enters the tissues to create ATP molecules and carbon dioxide exits.

Organs of the Respiratory Tract

The respiratory tract is divided into the upper respiratory tract (nasal cavity, pharynx, larynx) and the lower respiratory tract (trachea, bronchus, bronchioles, alveolus).

Lung Function

The lungs’ physiological function is due to their microscopic anatomy, with alveoli surrounded by a capillary bed for gas exchange.

Breathing Regulation

Breathing is regulated by central and peripheral chemoreceptors, responding to CO2 levels in the bloodstream. The hypothalamus also influences respiration.

Pleura Layers

Visceral pleura is connected to the lungs, while parietal pleura is connected to the thoracic cavity.

Inspiration and Expiration

Muscle contractions and relaxations control breathing, with accessory muscles involved in forced inspiration and expiration.

Other Air Movements

Coughing, sneezing, laughing, and yawning are examples of air movements beyond breathing.

Digestion

Digestion involves organs of the alimentary canal and accessory organs, with six stages: ingestion, propulsion, mechanical digestion, chemical digestion, absorption, and defecation.

Ingestion and Propulsion

Ingestion is food entry into the alimentary canal, followed by propulsion through peristalsis.

Mechanical and Chemical Digestion

Mechanical digestion breaks down food mechanically, while chemical digestion involves organs like the liver, pancreas, and gallbladder.

Stomach Movements

Mixing and peristalsis aid in food digestion in the stomach, with segmentation isolating and breaking down food.

Nervous System Influence

The parasympathetic and sympathetic nervous systems regulate gastric juice secretion.

Stomach Muscles and Functions

Oblique, circular, and longitudinal muscles aid in mechanical digestion, while rugae expand the stomach to store more food.

Digestive Enzymes

HCL, trypsin, intrinsic factor, and gastrin play roles in protein digestion and nutrient absorption.

Digestive Phases

Cephalic, gastric, and intestinal phases regulate the production of gastric juices during digestion.