Organs of the Digestive System

Organs of the Digestive System

• The digestive system consists of accessory organs and the alimentary canal.

Accessory Organs

• Salivary glands: Produce saliva containing enzymes for carbohydrate breakdown.
• Liver: Generates bile which emulsifies fats aiding digestion.
• Gallbladder: Stores and concentrates bile for release into the small intestine.
• Pancreas: Secretes pancreatic juice with digestive enzymes and bicarbonate into the small intestine.

Alimentary Canal

• Mouth: Initiates mechanical and chemical digestion of food, especially carbohydrates.
• Pharynx: Connects the mouth to the esophagus, facilitating food passage.
• Esophagus: Uses peristalsis to move food to the stomach.
• Stomach: Secretes acid and enzymes to mix with food, starting protein digestion.
• Small intestine: Finalizes enzymatic breakdown of food and is the primary site of nutrient absorption.
• Large intestine: Absorbs water and electrolytes, converting contents into feces.
• Rectum: Regulates fecal elimination.

Types of Movements in Alimentary Canal

• Mixing movements: Occur in the stomach to mix food with digestive juices.
• Segmentation: Occurs in the small intestine, mixes contents without unidirectional movement.
• Peristaltic waves: Propel food through the canal in a wavelike motion.

Teeth Development

• Teeth form within mandible and maxillae, with two sets developing during growth.
• Primary teeth: Erupt approximately between six months and four years, typically in an ordered sequence.
• Secondary teeth: Push primary teeth out as they develop, totaling thirty-two in adulthood.

Types of Teeth

• Primary teeth (20) consist of incisors, canines, and molars, while secondary teeth (32) include premolars and third molars (wisdom teeth).
• Functions of teeth: Breakdown food mechanically, increasing surface area for digestive enzymes.

Structure of a Tooth

• Composed of crown (covered by enamel) and root (attached to jaw by cementum and periodontal ligament).
• Enamel: Hardest substance, mainly made of calcium.
• Dentin: Living cellular tissue, harder than bone.
• Pulp cavity: Contains blood vessels and nerves.

Salivary Glands

• Saliva moistens food, initiates carbohydrate digestion, and helps cleanse the mouth.
• Major salivary glands include:
  • Parotid glands: Largest, producing watery saliva high in amylase.
  • Submandibular glands: Provide a mixed secretion, more viscous than parotid saliva.
  • Sublingual glands: Smallest, mainly secreting thick, mucous fluid.

Functions of Major Mouth Structures

• Cheeks: Form lateral walls, assist in holding and chewing food.
• Lips: Sensory structures for food characteristics.
• Tongue: Mixes food with saliva and aids in swallowing; contains taste receptors.
• Palate: Separates oral cavity from nasal cavity.

Clinical Notes

• Dental caries result from bacteria in sticky foods producing acids that deteriorate enamel and dentin. Prevention includes regular brushing, dental check-ups, and fluoride treatments.
• Tonsillitis can lead to swollen tonsils obstructing airways; tonsillectomies may be necessary if recurrent.

Layers of the Alimentary Canal Wall

• Mucosa: Protects tissue, secretes enzymes, absorbs nutrients.
• Submucosa: Nourishes surrounding tissues and transports absorbed materials.
• Muscularis: Controls movements of food along the canal.
• Serosa: Protects organs and provides lubrication.

Nervous System Innervation

• The alimentary canal is extensively innervated by sympathetic and parasympathetic fibers, regulating digestive activities.
• Parasympathetic impulses: Enhance motility and secretion.
• Sympathetic impulses: Reduce digestive activity.### Sympathetic vs. Parasympathetic Impulses
• Sympathetic impulses generally oppose digestive actions of the parasympathetic division.
• This results in decreased digestive activity during stress or flight situations.

Endoscopy Technician Career

• Young woman experienced complications after gastric bypass surgery, making her unable to eat more foods.
• Expectations of ability to eat varied significantly from outcome, shedding light on surgical impacts.

Terminology in Digestion

• Aliment: Refers to food; the alimentary canal is the digestive tract.
• Cari: Related to decay; dental caries indicates tooth decay.
• Cec: Refers to blindness; the cecum is a blind-ended sac of the large intestine.
• Chym: Refers to juice; chyme is a semifluid paste formed in the stomach.
• Decidu: Refers to falling off; deciduous teeth are those shed during childhood.
• Frenul: Means bridle; a frenulum is a fold anchoring the tongue.
• Gastr: Refers to the stomach; gastric glands secrete gastric juice.
• Hepat: Pertaining to the liver; hepatic duct carries bile from the liver.
• Hiat: Refers to opening; the esophageal hiatus allows esophagus passage through diaphragm.
• Lingu: Related to the tongue; the lingual tonsil consists of lymphatic tissue at tongue root.
• Peri: Means around; peristalsis is the muscle contraction that moves food along the canal.
• Pyl: Refers to gatekeeper; the pyloric sphincter controls passage between stomach and small intestine.
• Rect: Pertains to straight; the rectum is the distal part of the large intestine.
• Sorpt: Means to soak up; absorption is the uptake of substances.
• Vill: Refers to hairy; villi are tiny projections increasing surface area in the small intestine.

Overview of the Digestive System

• Digestion involves mechanical and chemical breakdown of food for cell absorption.
• Mechanical digestion reduces size without altering chemical makeup, while chemical digestion alters food into simpler chemicals.
• Functions include ingestion, propulsion, absorption, and defecation.
• The digestive system comprises the alimentary canal and accessory organs.

Anatomy of the Digestive System

• The alimentary canal is a muscular tube approximately 8 meters long, traversing thoracic and abdominopelvic cavities.
• Structure includes four layers: mucosa, submucosa, muscularis, and serosa, with variations based on the specific region's functions.
• The innermost layer, mucosa, consists of epithelium and connective tissue, with some areas having folds for increased absorptive capacity.

Explore the key components of the digestive system, focusing on the accessory organs such as salivary glands, liver, gallbladder, and pancreas. This quiz will test your knowledge of how these organs contribute to digestion and nutrient absorption.