Human Respiratory and Digestive Systems: Anatomy and Function

Respiratory System Divisions

Conducting Zone: Functional divisions, tubes of the conducting system.

Respiratory Zone: Site of gas exchange.

Pharynx

Location: Upper Respiratory.

Functions: Passageway for air and food, resonating chamber for emitted sounds, houses tonsils.

Anatomy: Extends from the nasal cavity to the larynx, includes the nasopharynx, oropharynx, and laryngopharynx. Composed of skeletal muscles and mucous membrane.

Larynx

Location: Lower Respiratory.

Function: Connects the pharynx to the trachea. Maintains an open airway, routes food and air, and assists in sound production.

Anatomy: Composed of 9 pieces of cartilage, including the thyroid cartilage and epiglottis.

Thyroid Cartilage

Part of the larynx. The vocal folds are located behind the thyroid cartilage.

Trachea

Location: Lower Respiratory.

Function: A tube connecting the larynx to the bronchi. Keeps the airway open.

Anatomy: Supported by C-shaped tracheal cartilages made of hyaline cartilage. Lined with ciliated epithelium.

Alveoli

Anatomy: Elastic sacs, approximately 150 million per lung, providing a large surface area.

Function: Site of gas exchange with the pulmonary capillary bed. Oxygen moves into the alveolar lumen, and carbon dioxide moves from the alveolar lumen to the blood.

Additional Notes: Cells secrete a surfactant, which is crucial for preventing infant respiratory distress syndrome.

Respiration Processes

Function: Includes vocalization in humans and the exchange of oxygen and carbon dioxide.

Four Processes:

• Ventilation
• External Respiration
• Internal Respiration
• Cellular Respiration

Digestive System Components

Esophagus

A muscular tube connecting the throat (pharynx) with the stomach. It is about 8 inches long and lined by moist pink tissue called mucosa.

Stomach

Functions:

• Bulk storage of ingested food (chyme).
• Mechanical breakdown of food through muscle layers (longitudinal, circular, oblique).
• Chemical breakdown of chyme, including protein digestion via enzymes, mucus, and hydrochloric acid.
• Production of intrinsic factor.

Duodenum

Function: Major site of digestion.

Receives: Enzymes from the pancreas and bile from the liver.

Liver

Functions:

• Regulates the chemical composition of blood.
• Produces and secretes bile, an emulsifier of fats.
• Produces a watery mixture containing electrolytes, cholesterol, bile salts, lecithin (a phospholipid), and pigments.
• Hepatic Portal System: Blood from the small intestines passes through the liver.

Cirrhosis: Damage to liver cells causing permanent impairment of liver function.

Gallbladder

Function: Stores and concentrates bile produced by the liver. Contraction forces bile into the common bile duct and then into the duodenum.

Gallstones: Crystallized cholesterol that can cause blockages.

Pancreas

(Details for the pancreas are not provided in the original text.)