lecture 19 Flashcards
Describe the major functions of the digestive system.
o Ingestion: The process of taking in food through the mouth.
o Mechanical breakdown: The physical breakdown of food into smaller pieces, such as chewing and churning in the stomach.
o Propulsion: Moving food along the digestive tract, including swallowing and the peristaltic movement of food down the esophagus and intestines.
o Chemical Digestion: The breakdown of food into simpler molecules by enzymes and acids, which allows nutrients to be absorbed.
o Absorption: The process by which nutrients, water, and minerals are absorbed into the bloodstream from the digestive tract, particularly in the small intestine.
o Defecation: The elimination of indigestible substances and waste products from the body as feces.
Explain the differences between the gastrointestinal (GI) tract (alimentary canal) and the accessory digestive organs.
Gastrointestinal (GI) Tract (Alimentary Canal):
Includes the mouth, esophagus, stomach, small intestine, large intestine, rectum, and anus.
It is the continuous tube through which food travels and is digested.
The primary function is to process and absorb nutrients from food.
Accessory Digestive Organs:
Include the salivary glands, liver, pancreas, and gallbladder.
These organs are not part of the GI tract but contribute essential fluids and enzymes to aid digestion.
The salivary glands secrete saliva to begin the breakdown of carbohydrates, the liver produces bile to emulsify fats, the pancreas secretes digestive enzymes and bicarbonate to neutralize stomach acid, and the gallbladder stores and concentrates bile.
Compare and contrast mechanical digestion and chemical digestion, including where they occur in the digestive system.
Mechanical Digestion:
o Involves the physical breakdown of food into smaller pieces.
o Occurs primarily in the mouth (through chewing) and the stomach (through churning).
o It does not change the chemical structure of food but increases surface area for chemical digestion.
Chemical Digestion:
o Involves the breakdown of food into simpler molecules by digestive enzymes and acids.
o Begins in the mouth with enzymes like amylase breaking down carbohydrates, continues in the stomach with the action of pepsin on proteins, and completes in the small intestine with enzymes from the pancreas and bile from the liver.
o Chemical digestion allows for the absorption of nutrients (like sugars, amino acids, and fatty acids) into the bloodstream.
Both mechanical and chemical digestion work together to
Both mechanical and chemical digestion work together to break down food for nutrient absorption. Mechanical digestion physically prepares the food, while chemical digestion breaks it down into molecular forms that the body can absorb.
Trace the pathway of ingested substances through the gastrointestinal (GI) tract.
o Mouth: Food is ingested and mechanically broken down by chewing. Saliva, which contains the enzyme amylase, begins chemical digestion, especially carbohydrates.
o Esophagus: After swallowing, food moves down the esophagus by peristalsis (wave-like muscle contractions) to reach the stomach.
o Stomach: The stomach further churns food and secretes gastric juices containing hydrochloric acid and pepsin, initiating the digestion of proteins. The food is turned into a semi-liquid substance called chyme.
o Small Intestine: The chyme enters the small intestine, where most of the digestion and nutrient absorption occurs. Enzymes from the pancreas break down fats, proteins, and carbohydrates. The liver secretes bile to emulsify fats.
o Large Intestine: Water and electrolytes are absorbed in the large intestine, and indigestible materials are prepared for excretion. Beneficial bacteria also help break down certain substances.
o Rectum and Anus: Finally, the indigestible remains are stored in the rectum and expelled from the body through the anus during defecation.
identify the lips
o Lips: Serve as the opening for the mouth. They help in the manipulation of food and speech formation.
hard palate
o Hard Palate: The bony part of the roof of the mouth. It provides a rigid surface for the tongue to push food against during chewing.
soft palate
o Soft Palate: The muscular portion at the back of the roof of the mouth. It rises to close off the nasal passages during swallowing to prevent food from entering the nasal cavity.
uvula
o Uvula: The small, fleshy projection hanging from the soft palate. It helps with speech and helps in preventing food from entering the nasopharynx during swallowing.
frenula
o Frenula (Plural: Frenulum): Small folds of mucous membrane that help anchor the tongue to the floor of the mouth (lingual frenulum) and the lips to the gums (labial frenulum).
gingivae
o Gingivae (Gums): The soft tissue surrounding the teeth, providing protection and support for the teeth.
tongue
o Tongue: A muscular organ responsible for moving food around the mouth during chewing, aiding in swallowing, and assisting in speech. It is also involved in the sensation of taste through taste buds located on its surface
Describe and order the layers of a general tooth.
o Enamel: The outermost layer, made of a hard, mineralized substance primarily composed of hydroxyapatite. Enamel is the hardest substance in the human body and protects the tooth from physical and chemical damage.
o Dentin: The layer beneath the enamel, made of a hard, bone-like material. Dentin is less mineralized than enamel but still provides structure and support for the tooth. It contains microscopic tubules that transmit sensations (such as pain).
o Pulp: The innermost part of the tooth, consisting of soft tissue that contains blood vessels, nerves, and connective tissue. The pulp provides nutrients to the tooth and is responsible for sensation (pain).
incisors
o Incisors (8 total): Located at the front of the mouth, they are flat and sharp, used for cutting food.
canines
o Canines (4 total): Pointed teeth located next to the incisors. They are used for tearing food.
premolars
o Premolars (8 total): Located behind the canines, premolars have flat surfaces with ridges and are used for crushing and grinding food.
molars
o Molars (12 total, including wisdom teeth): Located at the back of the mouth, these teeth have large, flat surfaces and are used for grinding food. Molars include the third molars, or wisdom teeth, which may or may not be present in some individuals.
the three major salivary glands
parotid
submandibular
sublingual
Describe the structure and function of the salivary glands.
o Parotid Glands: Located near the ears, these are the largest salivary glands. They primarily secrete a serous, watery saliva rich in enzymes, especially amylase, which begins the digestion of carbohydrates.
o Submandibular Glands: Located beneath the jaw, these glands produce both serous and mucous saliva. They secrete saliva that helps with both the initial digestion and lubrication of food.
o Sublingual Glands: Located under the tongue, these glands primarily produce mucous saliva, which aids in lubricating the mouth and forming a food bolus for easier swallowing.
composition of saliva
o Water: Makes up most of saliva and helps with moistening and lubricating food.
o Electrolytes: Sodium, potassium, calcium, and bicarbonate ions help maintain the pH of the mouth and neutralize acids.
Enzymes:
o Amylase: Begins the breakdown of starches into sugars.
o Lingual Lipase: Begins the digestion of fats, especially in the stomach.
o Mucins: Glycoproteins that help lubricate and protect the mucous membranes in the mouth and the digestive tract.
o Lysozyme: An antibacterial enzyme that helps control bacterial growth in the mouth.
o Immunoglobulins (IgA): Help protect against infections by binding to pathogens and preventing their attachment to tissues.
functions of saliva
o Lubrication: Facilitates the movement of food in the mouth and aids in swallowing.
o Digestion: The breakdown of carbohydrates begins through the action of amylase.
o Protection: Helps protect the teeth and mouth from harmful bacteria and acids by washing away food particles and neutralizing acids.
o Taste: Moistens food, allowing taste buds to function properly.
o Buffering: Helps maintain oral pH and prevent tooth decay by neutralizing acids.
functions of the salivary glands
The salivary glands produce and secrete saliva, which moistens and lubricates food, making it easier to chew and swallow. Saliva also contains enzymes like amylase to begin the breakdown of carbohydrates, and lysozyme, an enzyme that has antibacterial properties, helping protect against infections.
anatomy of the nasopharynx
Location: The uppermost part of the pharynx, located behind the nasal cavity.
Passage of Air: The nasopharynx serves as the passageway for air from the nasal cavity to the larynx. It also connects to the middle ear via the Eustachian tubes.
Passage of Food: The nasopharynx does not normally allow food to pass through it since food is directed into the oropharynx during swallowing.
anatomy of the oropharynx
Location: The middle portion of the pharynx, located behind the oral cavity.
Passage of Air: The oropharynx allows the passage of air from the nasopharynx to the larynx.
Passage of Food: The oropharynx is the primary area for the passage of food and liquids from the mouth to the esophagus during swallowing. It is where food is directed when you swallow.
