Lecture Two Flashcards
What are Accessory Organs?
Glands that secrete fluid into the digestive system.
What is the Components of the Digestive System in order?
- Oral cavity (mouth) Accessory organs= tonsils and salivary glands.
- Pharynx (throat).
- Oesophagus.
- Stomach.
- Small intestines= Duodenum, Jejunum, Ileum. Accessory organs= liver gallbladder and pancreas.
- Large intestines- cecum, colon, rectum and anal canal.
What are the Functions of the Digestive System?
- Ingestion
- Mastication
- Propulsion
- Mixing
- Secretion
- Digestion
- Absorption
- Elimination
What is Mastication?
Food is mechanically broken down to increase the total surface area to allow digestive enzymes to easily break down food.
What is Propulsion, Swallowing, Peristalsis and Mass Movements?
Propulsion-The movement of food through the digestive tract.
Swallowing-Moves the bolus (mass of liquid and soft food) from the oral cavity to the oesophagus.
Peristalsis-Wave of smooth muscle relaxation & contractions which expands the tract in front of the bolus.
-Process by which food moves through the gut.
Mass movements-Contractions that move material
-Large intestines
What is Mixing?
-Segmental contractions.
oSegments fluctuate between relaxation and contractions.
oPurpose is to mix the food with digestive secretions which assist with breaking in down into smaller pieces.
oSmall intestines.
What is Secretion?
-Purpose to digest, buffer, lubricate and liquefy
What is Digestion?
- Mechanical- Mastication and mixing
- Chemical- Digestive enzymes
What is Absorption?
-Molecules moving out of the digestive tract into the circulatory or lymphatic system.
What is Elimination?
-Waste products are eliminated from the body via defecation.
-Occurs in the large intestine, material is altered from a liquefied substance to semi-solid (faeces) substance by absorbing water and salts.
→Ultimate aim= the breakdown of large food molecules to smaller ones that can be absorbed into the circulatory system.
What are the types of Secretion?
oMucus- Entire digestive tract.
-Protects the epithelial cells from digestive enzymes, stomach acids and abrasion.
-Lubricates the lining of the tract and the food.
oWater
-Liquefies the food- easier to digest/absorb.
oEnzymes
-Secreted from pancreas, small intestines, stomach and oral cavity.
What is Chemical Digestion?
-Food we ingest needs to be broken down to smaller molecules.
-This occurs via chemical reactions.
oThese can occur naturally but are quite slow.
oRequires an enzyme.
oDefinition: a substance that increase the speed of a reaction without being changed or used up in the process.
-An enzyme is a type of catalyst.
→Protein.
What are the types of Enzymes?
- Amylase
- Breaks down carbohydrates. - Lipase
- Breaks down lipids. - Protease
- Breaks down proteins.
What affects Enzyme Function?
- Temperature
2. PH
What are the layers of the Digestive Tract?
- Mucosa
- Mechanoreceptors
- Chemoreceptors - Submucosa
- Nerves, lymphatic and blood vessels and small glands. - Muscularis
- Smooth muscle - Serosa
- Smooth layer that covers the digestive tract organs.
What are the Regulations of the Digestive Tract?
Nervous Regulation
-Enteric Nervous System (ENS)
oA division of the autonomic nervous system.
oLocated within the walls of the digestive tract.
oCan work independently of the autonomic nervous system.
Autonomic Nervous System
-Parasympathetic Nervous System
oRest and digest
oIncreases motility, salivary and gastric acid secretions.
-Sympathetic Nervous System
oFight or flight
oDecreases motility.
Chemical Regulation
-Endocrine secretions (hormones): gastrin, secretin and cholecystokinin.
What is the Oral Cavity?
-Mechanical & chemical digestion.
-Normal adult teeth number=32.
-Assists with the process of mastication (mechanical).
oIncisors & canines
-Tear & cut food.
oPremolars & molars
-Grind & crush food.
What is Saliva?
- 3 large salivary glands.
- 1-1.5L/day
- Watery/mucous secretion.
What are the Functions of Saliva?
- Keeps the oral cavity moist.
- Assists with the normal speech. - Suspension of food in a solution which aids taste.
- Begins digestion.
- Salivary Amylase-Starch splitting enzyme which breaks down 3-5% of carbohydrates.
- Lingual Lipase-Digests small amount of lipids. - Protective Functions
- Washes oral cavity.
- Contains bicarbonate ions= Neutralize acids from oral bacteria.
- Contains the enzyme lysozyme= Antibacterial properties which assists with preventing infection from bacteria.
What is the Parasympathetic Stimulation in Saliva?
-In response to taste, tactile stimuli & food odour.
What are the parts of the Pharynx?
- Nasopharynx
- Oropharynx
- Laryngopharynx
What is associated with Digestion in the Pharynx?
- Only the oropharynx & laryngopharynx are associated with digestion.
- Uvula prevents food material entering the nasopharynx.
What is the Epiglottis?
Covers the larynx to prevent food entering the respiratory passages. Connects pharynx to the stomach.
Where does the Oesophagus run?
- From pharynx to stomach.
- Posterior to the trachea.
- Travels through the opening (hiatus) of the diaphragm.
How is food controlled into & out the Oesophagus?
- Food into & out of the oesophagus is controlled by the upper & lower (cardiac) oesophagus sphincters.
- Upper is skeletal muscle & lower is smooth muscle.
What are the phases of swallowing?
- Voluntary
- Pharyngeal
- Oesophageal
Describe the phases of swallowing.
- Voluntary Phase
- The bolus is moved by the tongue against the hard palate & towards the oropharynx. - Pharyngeal Phase
- The soft palate elevates to close off the nasopharynx.
- The pharynx elevates, receives the bolus & moves it towards the oesophagus.
- The epiglottis closes over the larynx/trachea.
- Upper oesophageal sphincter relaxes. - Oesophageal Phase
- Peristaltic waves move food towards the stomach.
- Gravity is enough for liquid.
- Lower oesophageal sphincter relaxes.
What is the Pyloric Sphincter?
Regulates the release of food from the stomach into the small intestines.
In stomach histology, describe the submucosa & mucosa.
Submucosa & mucosa are folded, which assists with increasing its surface area & expands when the stomach receives food.