the digestive system

• - heaviest gland of the body
• - has right and left lobe
• - liver is composed of hepatocytes , bile canaliculi , hepatic sinusoids
• - another job of the liver is to clean out damaged RBCs

• - major functional cells of liver
• - wide variety of metabolic , secretory , and endocrine functions
• - secrete bile

• - ducts between hepatocytes that collect bile
• - collect bile from hepatocytes
• - bile then passed into bile ductules and then bile ducts
• - bile ducts merge to form right and left hepatic ducts which unite and exit the liver as common hepatic duct

• - highly permeable blood capillaries between row of hepatocytes
• - receive oxygenated blood from hepatic artery and deoxygenated nutrient-rich blood from hepatic portal vein

joins cystic duct from gallbladder to form common bile duct

• - portal triad
• - a bile duct branch of the hepatic artery and branch of the hepatic portal vein

• - store and concentrate bile , produced by the liver until it is needed in the small intestine
• - absorbs water and ions to concentrate bile up to ten-fold
• - contraction of smooth muscle fibers eject contents of gallbaldder into cystic duct

• - liver received blood from the hepatic artery carrying oxygenated blood
• - hepatic portal vein carry deoxygenated blood with newly absorbed nutrients , drugs , and pssibly microbes and toxins form GI tract

• - branches of hepatic artery and hepatic portal vein carry blod into liver sinusoids
• - oxygen , most nutrients , and certain toxic substances are taken up by hepatocytes
• - products manufactured by hepatocytes and nutrients needed by other cells are secreted back into the blood
• - sinusoid drains into central vein whic eventually passes into a hepatic vein

• - mostly water , bile salts , cholesterol , lecithin , bile pigments , and several ions
• - partially excretory product / partially digestive secretion
• - bile release increases during digestion
• -

• - emulsification
• - breakdown of large lipid (fat) globules into a suspension of small lipid globules
• - aids digestion and absorption of lipids in small intestine

• - principal bile pigment ( yellow )
• - derived from heme of recycles RBCs
• - breakdown product stercobilin gives feces brown color

• - synthesis and secretion of bile
• - carbohydrate metabolism
• - lipid metabolism
• - protein metabolism
• - processing fo drugs and hormone
• - inactivation of toxins
• - excretion of bilirubin
• - synthesis of plasma proteins
• - storage of vitamins and minerals
• - phagocytosis
• - activation of vitamin D

• - digestion and absorption of nutrients
• - large surface area
• - length 10feet living 21 feet in a cadaver
• - circular folds ( pilcae ) villi , and microvilli

• 1. duodenum
• 2. jejunum
• 3. lleum

• - simple columnar epithelium that contains many types of cells
• - absorptive cells : digest and absorb nutrients in chyme
• - goblet cell : secrete mucus
• - intestinal glands crypts of lieberkuhn : secrete intestinal juice
• - paneth cells : secrete lysozyme and are capable of phagocytosis destorys bactreria
• - solitary lymphatic nodules , peyer's pathes ( aggregated lympatic follicles )

- dudoenal ( brunner's ) gland

completely surrounded except for major portion of duodenum

• - fingerlike projections of mucosa
• - contains arteriole , venule , blood capillary and lacteal in lamina propria

• - projections of apical membrane of absorptive cells
• - brush border : forms a fuzzy line because too small to be seen individually with a light microsocope
• - brush border : enzymes

• 1-2 liters secreted daily
• - contains water and mucus , slightly alkaline
• - provide liquid medium aiding absorption

• - synthesized by and inserted into plasma membrane of microvilli of absorptive cells
• - some enzymatic digestion occurs at surface of cells rather than just in lumen
• - a-dextrinase , maltalse , sucrase, lactase : digest carbohydrates
• - aminopetidase , dipeptidase : digest proteins
• - nucleosidases and phosphatases: digest nucleotides

• - myenteric plexus
• - segmentaions: localized , mixing contractions , mix chyme and bring it in contact with mucosa for absorption
• - begins in lower portion of stomach and pushes chyme forward

• - partially digested carbohydrates , proteins , and lipids
• - completion of the digestion is a collective effort of pancreatic juice , bile and intestinal juice in the small intestine

• - pancreatic amylase
• - a-dextrinase , sucrase , lactase , maltase in brush border
• - ends with monosaccharides which can be absorbed

• - trypsin
• - peptidases ( aminopeptidase and dipeptidase ) in brush border

- complete absorption , produce certain vitamins and form and expel feces

• cecum
• colon
• rectum
• anal canal

• ascending
• transverse
• descending
• sigmoid

• -anus
• - guarded by internal anal sphincter of smooth muscle = interanl involuntary
• - and exteranl anal sphincter of skeletal muscle = external voluntary

• - mucosa : simple columnar epithelium with mostly absorptive and goblet cells
• - arranged in tubular intestinal glands ( crypts of lieberkuhn )
• - no circular folds or villi
• - has microvilli on the absorptive cells
• - muscularis : longitudinal muscle modified to form three bands called teniae coli
• - forms haustra ( pouches ) which gives puckered appearance to colon

• - haustra fill up , contract and squeeze contents into next haustrum when distension reaches a certain point
• - peristalsis : slower than in more proximal portion of tract
• - mass peristalsis : starts in middle of transeverse colon and quickly drives contents of colon toward rectum
• - stimulated by food in stomach ( gastrocolic reflex )

• - no enzymes are secreted
• - ferment carbohydrates
• - produce some B vitamins and vitamin K
• - convert any remaining proteins into simpler substances
• - release hydrogen , carbon dioxides , and methane gases ( flatus )

gives feces their brown color

remaining water absorbed along with ions and some vitamins

• water
• inorganic salts
• sloughed off epithelial cells from mucosa of GI tract
• bacteria
• products of bacterial decomposition
• unabsorbed digested materials
• indigestible parts of food

• - empties of rectum
• - stretch receptors and initialtes defecations reflex
• - increasing pressure of longitudinal rectal muscles voluntary contractions of diaphragm and abdominal muscles opens internal anal sphincter
• - if external anal sphincter is voluntarily relaxed defecation occurs and feces are expelled
• - if external anal sphincter is voluntarily constricted decrecation is postponed

• - defecation
• - increase in frequency , volume , and fluid content of feces
• - caused by increased motility of and decreased absorption by intestines
• - can result in dehydration and electrolyte imblances

• - defecation
• -infrequent of difficult defecation
• - caused by decreased motility of intestines
• - excessive water absorption occurs and feces become dry and hard

• - cephalic phase
• - gastric phase
• - intestinal phase

• - smell , sight , thought or initial taste of food activated neural centers
• - sitmulates salivary glands and gastric glands
• - prepares mouth and stomach for food to be eaten

• - begin one food reaches the stomach
• - neural and hormonal mechanisms promote gastric secretions and motility
• - stretch receptors detect distension
• - chemoreceptors detect change in pH
• - activate parasympathetic and enteric neurons and release of gastrin form G cells
• - gastrin stimulates release of large amounts of gastric juice
• - HCL lowers pH

• - begins when food enters small intestine
• - slows exit of chyme from stomach
• - prevents small intestine from being overloaded with more chyme than it can handle
• - distension of duodeum singnals nervous system to inhibit gastric motility ( enterogastric reflex )
• - stimulates flow of bile and pancreatic juice
• - mediated by two hormones secreted by small intestine
• - cholecystokinin ( CCK )
• - secretin

• - emulsification by bile salts increases surface area
• - bile salts are amphipathic , they have both hydrophobic and hydrophilic regions
• - break large lipid globules down into serveral small lipid globules
• - gallbladder

triglyceride digestion

- ribonuclease and dexoyribonuclease in pancreatic juice

- passage of digested nutrients for GI tract through absorptive epithelial cells of mucosa and into blood or lymph

• . diffusion
• . facilitated diffusion
• . osmosis
• . active transport

digested and absorbed

- simple diffuison

liver and adipose cells for storage of triglycerides

- compounds that separate into ions in water and conduct electricity , has a charge

• A
• D
• E
• K
• - absorbed by simple diffusion and transported with lipids in micelles

• B
• C
• - absorbed by simple diffusion

• - comes from ingestion
• - GI secretions
• - most absorbed in small intestine , some in the large intestine
• - only 100ml excreted in feces
• - all water absorption occurs by osmosis

- is all the chemical reactions that occur in the body

- metabolic reactoins harvest chemical energy from consumed nutrients to contribute to the body's growth , repair , and normal functioning

1. supply energy for sustaining life processes: active transport , DNA replication , protein synthesis , muscle contraction, maintenance of body temperature , mitosis

2. building blocks for synthesis of more complex structural or functional molecules : muscle proteins , hormones , enzymes

3. stored for future use : glycogen and triglycerides

- break down complex molecules

produce more energy than comsumed the of the energy is coverted into heat

combine simple molecules into complex ones

comsume more energy than they produce

• - links anabolic and catobolic reactions for energy balance
• - fuels chemical reactions
• - energy currency

• - removal of electrons from a compound
• - decreases in potential energy
• - liberated hydrogen atom transfereed immediately by coenzymes to another compound

• - nicotinamide adenine dinucleotide
• - flavin adenine dinucleotide

both carry and transfer molecules

removal of hydrogen atoms

- addition of a phosphate group increases the potential energy for a molecule

• - fate of glucose depends on needs of body cells
• - ATP production or synthesis of amino acids , glycogen or triglycerides
• - insulin causes insertion of more of these transporters in plasma membrane , increasing rate of entry into cells
• - glucose is phosphorylated after entering a cell and beomes trapped with in cell

• 1. glycolysis
• 2. formations of acetyl coenzyme A
• 3. krebs cycle
• 4. electron transport chain