Digestive System Lecture Notes
Introduction to Digestion
- Digestion involves two main processes:
- Mechanical Digestion: Grinding food, starting with teeth; involves mixing and moving food through stomach contractions.
- Chemical Digestion: Utilizes enzymes to break down macromolecules.
- Digestive system functions include:
- Ingestion
- Propulsion
- Absorption
- Defecation
Components of the Digestive System
-
Alimentary Canal: The main food passageway from mouth to anus; includes:
- Mouth
- Pharynx
- Esophagus
- Stomach
- Small Intestine
- Large Intestine
- Anal Canal
- A muscular tube approximately 8 meters long.
-
Accessory Organs: Support digestion by providing secretions to the alimentary canal, includes:
- Salivary Glands
- Gallbladder
- Pancreas
Structure of the Alimentary Canal Wall
- Composed of four layers (innermost to outermost):
- Mucosa: Contains mucus membrane with folds to increase surface area for nutrient absorption.
- Submucosa: Nourishes cells and transports absorbed food molecules.
- Muscularis: Involved in non-directional and peristaltic movements.
- Serosa: Outermost layer with visceral peritoneal covering.
Movements in the Alimentary Canal
- Mixing Movements: Occurs in stomach and small intestines; non-directional, ensures enzymes coat food.
- Propelling Movements (Peristalsis): Directional movement resembling squeezing a marble through a balloon; involves rhythmic contractions.
Innervation of the Alimentary Canal
- Parasympathetic Nervous System: Involved in rest and digest functions, controlling secretion and motility.
- Sympathetic Nervous System: Can inhibit digestive processes to prioritize other bodily needs.
- Submucosal Plexus: Controls secretion.
- Myenteric Plexus: Controls gastrointestinal motility.
Endocrine Regulation
- Enteroendocrine Cells: Located in the stomach and secrete hormones to regulate digestive processes.
Note: Further details on digestive system functions and examples will be covered in subsequent sections of the lecture.