Digestive System PDF

- Lips & cheeks help keep food between teeth during chewing - Partial digestion of starches in mouth by salivary amylase - Mouth & associated parts function to begin mechanical breakdown of food (with some chemical breakdown) and creates a soft, flexible bolus for easy swallowing - Manipulat...

- Lips & cheeks help keep food between teeth during chewing - Partial digestion of starches in mouth by salivary amylase - Mouth & associated parts function to begin mechanical breakdown of food (with some chemical breakdown) and creates a soft, flexible bolus for easy swallowing - Manipulated by tongue, ground by teeth, mixed with salvia Separates oral cavity from nasal cavity, makes it possible to chew and breathe simultaneously - As well as a rigid shelf against which the tongue can push food - Created by the maxillary & palatine bones of the skull - In the posterior oral cavity, the tissue becomes fleshier (soft palate) - Composed mainly of skeletal muscle - Can manipulate the soft palate - to yawn, swallow, or sing During swallowing soft palate & uvula move upwards & close off nasopharynx - Prevent swallowed food/drink from entering nasal cavity Tongue: Skeletal muscle wrapped with mucous membrane - Helps to move food around mouth & towards back of mouth for swallowing - Most surfaces covered with papillae, which contain taste buds Lingual frenulum also limits posterior movement of tongue - Also site of tongue-tie The tongue is attached to the mandible, the styloid processes of the temporal bones, and the hyoid bone Internal nares to esophagus & larynx - Skeletal muscle, lined by mucous membrane - Involuntary muscle contractions close off the air passageways - Stratified squamous epithelium with mucous-producing glands - During swallowing muscles of the pharynx raise & expand pharynx to receive food bolus -Soft palate & uvula also rise to close off the nasopharynx - Larynx is pulled superiorly & the epiglottis folds inferiorly, covering the glottis Alternating muscular contractions create peristalsis Longitudinal & circular layer of muscles produce alternating contraction to create peristalsis - Oropharynx is involuntary during swallowing Gravity does not have any part in transport of food once it has left the mouth - In cells of walls of duodenum - Respond to food & partial digestion of food - Mostly all meant to turn off stomach cells & activities Digestion: Food being physically & chemically broken down & converted into substances suitable for absorption & assimilation into body/cells Chemical digestion involves enzymatic breakdown Metabolism: All of the physical and chemical processes in an organism by which its substance is produced, maintained, destroyed, and by which energy is made available Metabolism: All of the physical and chemical processes in an organism by which its substance is produced, maintained, destroyed, and by which energy is made available “Splitting sugar” Cytoplasm = all contents inside the cell membrane Cytosol = intracellular fluid within a cell  - Proteins, amino acids, mRNA, ribosomes, sugars, ions, cytoskeleton Energizes glucose to facilitate splitting into pyruvic acid Net gain of 2 ATP for each glucose molecule oxidized Also results in 2 energized coenzymes, 2 pyruvic acids - When oxygen is limited or absent, pyruvate enters an anaerobic pathway - In these reactions, pyruvate can be converted into lactic acid - Anaerobic respiration occurs in most cells of the body when oxygen is limited or mitochondria are absent or nonfunctional - For example, because erythrocytes (red blood cells) lack mitochondria, they must produce their ATP from anaerobic respiration. - This is an effective pathway of ATP production for short periods of time, ranging from seconds to a few minutes. - The lactic acid produced diffuses into the plasma and is carried to the liver - Where it is converted back into pyruvate or glucose Phosphorylation = addition of a Phosphate group to a molecule Occurs in Mitochondrial Matrix Transfers high-energy phosphate group to ADP - Substrate-level phosphorylation The pyruvate molecule generated during glycolysis moves from the cytoplasm into the mitochondrial matrix, where it is converted into acetyl coenzyme A (acetyl CoA) molecule. - Releasing carbon dioxide Acetyl CoA enters the Krebs cycle by combining with oxaloacetate, to form molecule citrate, or citric acid, at the same time releasing the coenzyme A molecule. For each turn of the cycle one ATP is created. Each carbon of pyruvate is converted into CO2, which is released as a byproduct of oxidative (aerobic) respiration oxidative phosphorylation, the final stage of cellular respiration Electrons passed from one molecule to another - Energy released in each electron transfer (forms electrochemical gradient) If oxygen isn’t present electron transport chain will stop running The electron transport chain (ETC) uses the coenzymes produced by the Krebs cycle to generate ATP. Electrons from previous pathways are transferred through protein complexes embedded in the inner mitochondrial membrane Each of passing/moving of electrons releases a small amount of energy, which is used to power special proteins that convert ADP to ATP  Mixes Ingestschyme food with digestive juices secreted Chews and mixes food from pancreas, gallbladder, Moistens and dissolves food, Begins chemical breakdown of allowing you to taste it and small intestine carbohydrates with secretion Mouth Propels Cleans and lubricates the teeth of salivafood at a rate slow enough for digestion and absorption and oral optimal Provides cavity medium for Small intestine Moves food into the pharynx Absorbs breakdown products of enzymatic Has some activity antimicrobial activity Begins breakdown carbohydrates, of lipids proteins, lipids, and via lingual lipase nucleic acids, along with vitamins, minerals, and water Performs physical Propels food fromdigestion the oral Pharynx via segmentation Lubricates food and passageways cavity to the esophagus Esophagus Liver: Propelsproduces food to bile the salts, which stomach Lubricates food and passageways emulsify lipids, aiding their digestion and absorption Bicarbonate-rich pancreatic juices help neutralize acidic chyme and Accessory organs Gallbladder: Mixes and churns stores,food with gastric concentrates, juices secreted provide optimal environment for and releases bilefrom epithelium to form chyme enzymatic activity Pancreas: produces digestive enzymes Begins chemical breakdown of and bicarbonate Stimulates protein-digesting proteins enzymes Stomach Releases food into Secretes intrinsic factor required Further breaks down food residues the duodenum as chyme for vitamin Food residueB12 absorption inand is concentrated small Absorbs most residual water, Absorbs some fat-soluble intestine stored prior temporarily electrolytes, and vitamins produced Large intestine substances (for example, alcohol, to defecation by enteric bacteria aspirin) Mucus eases passage Propels feces toward rectum Possesses antimicrobial functions of feces through colon Eliminates feces Body system Benefits received by the digestive system Cardiovascular Blood supplies digestive organs with oxygen and processed nutrients Endocrine hormones help regulate secretion in digestive glands and accessory Endocrine organs Skin helps protect digestive organs and synthesizes vitamin D for calcium Integumentary absorption Mucosa-associated lymphoid tissue (MALT) and other lymphatic tissue defend Lymphatic against entry of pathogens; lacteals absorb lipids; and lymphatic vessels transport lipids to bloodstream Muscular Skeletal muscles support and protect abdominal organs Sensory and motor neurons help regulate secretions and muscle contractions in Nervous the digestive tract Respiratory Respiratory organs provide oxygen and remove carbon dioxide Skeletal Bones help protect and support digestive organs Kidneys convert vitamin D into its active form, allowing calcium absorption in the Urinary small intestine