Digestive System PPT

Functions of the Digestive System

• Ingestion: This is the crucial first step of the digestive process, encompassing the intake of food through the mouth. The structure and activity of the lips and cheeks aid in gathering and positioning food, ensuring it is ready for processing. The act of ingestion is not only about taking in food but also about initiating the digestive process through mechanical breakdown.

• Digestion: This phase consists of two main components: mechanical and chemical digestion. Mechanical digestion involves processes such as chewing (mastication) that physically break food into smaller pieces, making it easier to digest. In the stomach, food is further mixed and churned with digestive juices. Chemical digestion requires the action of various enzymes that break food down into its molecular components, such as carbohydrates, proteins, and fats, enabling their absorption.

• Absorption: A vital process that takes place mainly in the small intestine, absorption is where the dissolved nutrients from digested food enter the bloodstream or lymphatic system. The small intestine is lined with tiny, finger-like projections called villi and microvilli, which greatly increase its surface area, facilitating more efficient absorption of nutrients like amino acids, simple sugars, and fatty acids into the body.

• Defecation: This is the final stage in the digestive process, involving the expulsion of indigestible waste material from the body. The process includes the formation of feces in the large intestine and ultimately their elimination through the anus. Defecation is essential for maintaining the body's internal environment by removing substances that are no longer needed, thus preventing toxic buildup.Digestion: This process involves the mechanical and chemical breakdown of food into smaller components that the body can absorb and utilize. It begins in the mouth with chewing and salivation, continues in the stomach where gastric juices further digest food, and is completed in the small intestine where enzymes break down complex molecules into simpler absorbable forms.

Organs of the Digestive System

• Two main groups of organs:

  • Alimentary canal (GI tract): This is a continuous coiled hollow tube that serves as the primary pathway for the digestive process. It extends from the mouth to the anus and is responsible for four key functions: ingestion, digestion, absorption, and defecation.

    • Ingestion occurs as food enters the mouth, where it is mechanically broken down and mixed with saliva.

    • Digestion happens throughout the canal, with both mechanical and chemical processes transforming food into absorbable nutrients.

    • Absorption takes place mainly in the small intestine, where nutrients are absorbed into the blood and lymphatic systems.

    • Defecation is the final step, where waste is excreted through the anus.

  • Accessory digestive organs: These include a variety of organs that assist in the digestive process but are not part of the alimentary canal.

    • Teeth: These structures masticate or chew food, breaking it down into smaller pieces and increasing its surface area, which facilitates enzymatic action during digestion. Humans have two sets of teeth: deciduous (primary) teeth and permanent teeth that replace them.

    • Tongue: An essential muscular organ that aids in the manipulation of food within the mouth and assists with the mechanics of swallowing by pushing the food towards the pharynx. The tongue also contains taste buds, which are crucial for detecting savoriness, sweetness, acidity, and bitterness of the food.

    • Salivary glands: These glands produce saliva, which contains enzymes like amylase that initiate the chemical breakdown of carbohydrates, lubricate food for easier swallowing, and have antibacterial properties to protect the oral cavity.

    • Pancreas: This gland has both endocrine and exocrine functions; it produces a range of digestive enzymes that are secreted into the small intestine and are critical for the digestion of all major food groups, including carbohydrates, proteins, and fats. It also secretes hormones such as insulin and glucagon that regulate blood sugar levels.

    • Liver: The largest gland in the body, it plays multiple roles including the production of bile, which is crucial for the emulsification of fats in the small intestine. The liver also metabolizes nutrients, detoxifies substances, and stores vitamins and minerals essential for the body's various functions. The gallbladder, which stores bile produced by the liver, releases bile into the duodenum during digestion to aid in fat absorption.

Organs of the Alimentary Canal

• Major organs:

  • Mouth

  • Pharynx

  • Esophagus

  • Stomach

  • Small intestine

  • Large intestine

  • Anus

Anatomy of the Mouth (Oral Cavity)

• Lips (labia): Protect the anterior opening.

• Cheeks: Form the lateral walls.

• Palates:

  • Hard palate: Anterior roof.

  • Soft palate: Posterior roof; contains uvula, which is a fleshy projection.

• Vestibule: Space between lips and teeth.

• Oral cavity proper: Area contained by teeth.

• Tongue: Attached to hyoid bone and floor of mouth by lingual frenulum.

• Anatomical Structures: Includes hard palate, soft palate, uvula, and tonsils.

Physiology of the Mouth

• Mastication: Chewing food.

• Mixing with Saliva: Helps with digestion and lubrication.

• Initiation of Swallowing: Tongue plays a crucial role.

• Sense of Taste: Enabled by the presence of food in the mouth.

Pharynx Anatomy and Physiology

• Anatomy:

  • Nasopharynx: Not part of the digestive system.

  • Oropharynx: Posterior to the oral cavity.

  • Laryngopharynx: Leads to the esophagus.

• Physiology: Acts as a passageway for air and food; food propelled to esophagus by two muscle layers (peristalsis).

Esophagus Anatomy and Physiology

• Anatomy: Approximately 10 inches long; extends from pharynx to stomach through diaphragm.

• Physiology: Conducts food via peristalsis; serves as a passageway for food only.

Stomach Anatomy

• Location: Left side of the abdominal cavity.

• Regions:

  • Cardiac region: near the heart.

  • Fundus: expanded portion lateral to the cardiac region.

  • Body: midsection.

  • Pylorus: funnel-shaped end into the small intestine.

• Functionality: Temporary storage, mixing, and digestion of food; can hold approximately 4L.

Stomach Physiology

• Function: Temporary storage tank; initiates protein breakdown via gastric juice.

• Components of Mucosa (simple columnar epithelium):

  • Mucous neck cells: Produce alkaline mucus.

  • Gastric glands: Secrete gastric juice (including pepsinogens and hydrochloric acid).

Small Intestine Anatomy and Physiology

• Major Digestive Organ: Long muscular tube for nutrient absorption; divided into duodenum, jejunum, and ileum.

  • Villi and Microvilli: Increases surface area for absorption.

• Chemical Digestion: Begins here with enzymes from both intestinal cells and pancreas.

Large Intestine Anatomy

• Structure: Larger diameter but shorter than small intestine; includes cecum, colon, rectum, and anal canal.

• Colon Subdivisions: Ascending, transverse, descending, and sigmoid colon.

• Function: Absorption of water and remaining nutrients; formation and elimination of feces.

Accessory Digestive Organs

• Teeth: Masticate food; two sets (deciduous and permanent).

• Salivary Glands: Produce saliva containing enzymes (amylase) to aid in digestion.

• Pancreas: Produces a wide range of digestive enzymes secreted to the duodenum; also secretes insulin and glucagon.

• Liver: Largest gland; produces bile for fat emulsification, with stored bile in the gallbladder.

Functions of the Digestive System Summary

• Mechanical Digestion: Chewing, churning, and segmentation.

• Chemical Digestion: Enzyme action breaking down food into building blocks (carbohydrates, proteins, fats).

• Absorption: Nutrients absorbed into blood and lymph; waste eliminated in feces.