The digestive system
Gastrointestinal (GI) tract
- continuous two with two openings (mouth and anus) -does not enter the body until it is absorbed
Three reasons for secretion
-Breakdown food -balance pH level -liquefies food
What does the tongue do
-Helps to position the food during mastication(chewing) -gathers the chewed food and a ball (bolus) in preparation for swallowing it
Propulsion
-Movement of food along digestive tract -gets it from point a to point B -The major meaning of propulsion is peristalsis
Additional churning in stomach
-Occurs in small intestine through muscular construction of intestinal wall -this process, segmentation is similar to peristalsis
Mechanical digestion
-Process of physically breaking down food into smaller pieces -begins with chewing food and continues with muscular churning of stomach
Tongue
-define slower boundary of them out -tongue covered in papillae (small projections that help get the food-many bare taste buds)
Pharyngeal phase
-involuntary -uvula protect nasal cavity -epiglottis goes down and protect -food goes to the esophagus
Absorbtion
-movement of molecules from digestive track two adjacent blood and lymphatic vessels (by passive defusion/active transport) -entrance of the digested food in the body
Chemical digestion
-process of chemically breaking down food into smaller molecules -carried out by enzymes in the stomach and small intestine and mouth
Meaning of peristalsis
-process of moving food forward Series of alternating contractions and relaxtions of smooth muscle that lines the walls of the digestive organs and that forces you to move forward
Segmentation
-similar to peristalsis except rythmic timing of the muscle constrictions -process of moving food back-and-forth
Palate
-upper boundary of mouth -front part=hard -back part=soft
Buccal phase
-voluntary -Tongue makes bolus -pushes bolus and to throat
Large intestine
5 to 6 feet long, 2.5 inches wide, last 7 to 8 inches is rectum -major iron absorbed: soldium -no chemical digestion occurs -absorbs vitamins for metabolic process
Three phases of swallowing
Buccal, pharyngeal, esophageal
Bile duct
Comes from gallbladder, enzymes enter through the ducks in the laws of gland and from pancreas
Parts of small intestine
Duodenum, jejenum and ileum
Jejenum an ileum
Finishes digestion but mainly absorption and small intestine
Saliva
Has water, enzymes, lysosomes, proteins, anti-bodies -lubricates mouth, softens food when chewing, protects mouth against pathogens, begins chemical digestion
Villi and microvilli
Increases surface area and contains capillaries and lymphatic vessels
Seven steps
Ingestion propulsion secretion mechanical digestion chemical digestion Absorption defication
Esophagus
Long tube that begins at laryngopharynx all the way down thru the cavity between the lungs, moves food down
Teeth
Lower and upper jawbone -incisors; biting -canine; tearing -premolars and molars; grinding and crushing
Liver
Makes bile, Controls breakdown of sugar, vitamin storage, remove drugs and hormones from body
Pancreatic duct
Merges into hepatopancreatic ampulla
Process of the G.I. tract
Mouth -> pharynx -> esophagus -> stomach -> small intestine -> large intestine
Controlled release
Movement of chyme into smaller intestine is regulated by The valve pyloric sphincter
Vestibule
Narrow region between the cheek and Teeth and between the lips and teeth
Gastric juices
Needed to activate enzymes, helps break down food into smaller pieces
Bile
Neutralizes stomach acids
Ingestion
Process of eating
Defication
Process of eliminating undigested material through the anus
Chemical breakdown
Proteins chemically breakdown by enzyme pepsin. It doesn't self digest do to mucus layer
Function of large intestine
Reabsorbs water and ions and compact feces
Duodenum
Receives spurts of chyme released from stomach through the pyloric sphincter
Pancreas
Secretes pancreatic juices to help break down food into tiny pieces
Secretion
Secretion Of digestive enzymes and other substances liquefies, Adjust the pH of, and chemically break down the food
Mixing
Stomach mixes the food with water and gastric juice to make chyme
Five functions of the stomach
Storage, mixing, physical breakdown, chemical breakdown, controlled release
Feces
Stores and compacts undigested material
Gallbladder
Stores bile until needed
Accessory organs
Teeth, tongue, salivary glands, liver, gallbladder, pancreas
Uvula
Tell writes back of pilot, prevents food going into your nasal passage while swallowing
Storage
The rugae lets the stomach expand
Physical breakdown
Three layers of smooth muscle churn contents of the stomach, physically breaking down food into smaller particles
Muscles
Three layers of smooth muscle, helps churn food
pharynx
Throat, receives food from mouth during swallowing
What does HCL do
Unfolds proteins and loosens The cementing substances between the cells that HCl also kills most bacteria that may accompany the food
Esophageal phase
When esophageal sphincter closes food passes thru larynx, when food reaches the end cardiac sphincter opens to let food goni to the stomach
Hepatopancreatic ampulla
Where the pancreatic duct and bile duct meat
Importance of temporary storage
You eat faster than you digest food and absorb its nutrients