PCOM: Anatomy 2 - week 4, The Digestive System
brush border enzymes
enzymes in the brush border that complete the digestion of carbs and proteins on the SI
Peptic or gastric ulcers
erosions of stomach wall; Most caused by helicobacter pylori bacteria (Chronic stress)
Crown
exposed part aboe gingiva(gum) Covered by enamel- hardest substance in body (calcium salts and hydroxyapatite crystals)
macronutrients
fat, protein, carbohydrates
epiglopic appendages
fat-filled pouches in the visceral peritoneum
Soft palate
fold formed mostly of skeletal muscle; closes off nasopharynx during swallowing.
chyme
food broken down to a mushy liquid for processing
another term for the alimentary canal
gastro intestinal tract (GI tract)
Pulp cavity
surrounded by dentin
how bile typically enters the small intestine
when the gall bladder contracts
pyloric canal
where the pyloric region narrows as it leads to the pylorus
Filiform
whitish, give the tongue roughness and provide friction; do not contain taste buds
Dental plaque
(film of sugar, bacteria and debris) adheres to teeth Acid from bacteria dessolves calcium salts
Types of extrinsic salivary glands
Parotid submandibular sublingual
Enzymatic digestion of proteins by?
Pepsin
Root
Portion embedded in jawbone
major regions of the stomach
cardiac, fundus, body, pyloric
three areas of the pyloric region
pyloric antrum, pyloric canal, pylorus
what lines the wall of the abdomino-pelvic cavity
parietal peritoneum
mucosa
in the center of the alimentary canal; lines lumen
Active
Absorption of nucleic acids uses what kind of transport?
What is the muscularis externa responsible for?
For segmentation(Mixing) and peristalsis (Movement)
Lesser Omentum
From liver to lesser curvature
What is B12 needed for?
Mature red blood cells
True
T/F The Vagus nerve is parasympathetic
What do gastric glands produce?
Gastric juice
Extrinsic salivary glands
Produce most saliva; lie outside oral cavity
Intestinal juice
1-2 L secreted daily in response to distension or irritation of mucosa; Facilitates transport and absorption of nutrients
Digestive process; Six essential activities
1. Ingestion 2. Propulsion 3. Mechanical Breakdown 4. Digestion 5. Absorption 6. Defecation
size of the adult stomach
15-25 cm long with diameter and volume dependent on its contents
Composition of saliva
97-99.5% water, slightly acidic Salivary amylase (cuts carbs) Mucin metabolic wastes- urea and uric acid
Three chemicals in regulation of gastric secretion
ACh, histamine and gastrin- Stimulate parietal cells through second messenger systems; all three are necessary for maximum HCI secretion
Parotid Gland
Anterior to ear; external to masseter muscle
Sublingual gland
Anterior to submandibular gland under tongue
Duodenum
Bile duct(from liver) and main pancreatic duct (from pancreas)
Dentin
Bonelike material under enamel; maintained by odontoblasts of pulp cavity.
Molars
Broad crowns, rounded cusps- best grinders
Premolars(bicuspids)
Broad crowns, rounded cusps- grind/crush
Incisors
Chisel shaped for cutting
Stomach delivers what to the small intestine?
Chyme (liquid food)
Absorption of lipids
Cluster with bile salts and lecithin to form Miceles; enter lacteals; transprted to systemic circulation
Bile ducts
Common hepatic duct (leaves liver) Cystic duct (Connects to gallbladder) Bile duct
Greater Omentum
Contains fat deposits and lymph nodes; Greater curvature --->over small intestine---> Spleen & transverse colon---> Mesocolon
fundus (stomach)
Dome-shaped region beneath diaphragm
What joins stomach at cardial office?
Esophagus
Jejunum
Extend from duodenum to ileum
Vomiting (emesis) Caused by?
Extreme stretching or intestinal irratants
T/F The colon is essential for life
False
Canines
Fanglike teeth that tear or pierce
As chyme enters duodenum...
Fatty chyme remains in duodenum 6 hours or more
Glands located where in the stomach produce the most gastric juice?
Fundus and body
Oral (buccal) Cavity
Lines with stratified squamous epithelium; most protective epitelium
Celiac disease
Gluten-sensitive entropathy Immune reaction to gluten
Intrinsic factor
Glycoprotein required for absorption of vitamin B12 in small intestine.
Denaturation of proteins happen by?
HCI Hydrochloric Acid
Liver lobules
Hexagonal structural and functional units Composed of plates and hepatocytes (liver cells) Filter and process nutrient-rich blood
Periodontitis(From neglected gingivitis)
Immune cells attack intruders and body tissues; destroy periodontal ligament
Sphincters
Internal anal Sphincter-smooth muscle External anal sphincter- Skeletal muscle
Ileum
Joins large intestine at ileocecal valve
Liver
Largest gland in the body; four lobes-right, left, caudate, and quadrate
Mesenteries of the stomach
Lesser Omentum Greater Omentum
appendix
Masses of lymphoid tissue; Part of MALT of immune system
Perostalsis
Meal remnants, bacteria and debris moved to large intestine
Submandibular gland
Medial to body of mandible
body (stomach)
Midportion
villi
Motile fingerlike extensions (~1mm high) of mucosa with capillary bed and lacteal(absorbs chyle) for absorption
Hard palate
Palatine bones and palatine processes of the maxillae
Serous membrane of abdominal cavity
Peritoneum
Lack of intrinsic factor can lead to?
Pernicious anemia
Gingivitis
Plaque calcifies to form calculus(tartar); Calculus disrupts seal between gingivae and teeth
haustra
Pocketlike sacs caused by tone and teniae coli
cecum
Pouch with attached vermiform appendix
Cirrhosis
Progressive, chronic inflammation from chronic hepatitis or alcoholism
What is the only stomach function essential to life?
Secretes intrinsic factor for Vitamin B12 absorption
Circumvallate (vallate)
V-shaped row in back of tongue; contain taste buds
What is the major organ of digestion and absorption?
Small intestine
Gallbladder
Stores and concentrates bile by absorbing water and ions; smooth muscular contractions release bile via cystic duct, which flows into bile duct
What type of tissue does esophageal mucosa contain?
Stratified squamous epithelium
Cardial part (cardia) (stomach)
Surrounds cardial orifice
Falciform Ligament
Suspends liver from diaphragm and anterior to abdominal wall
Common hepatic and cystic ducts
The bile duct is formed by union of common hepatic and cystic ducts
teniae coli
Three bands of longitudinal smooth muscle in muscularis
rectum
Three rectal valves stop feces from being passed with gas (flatus)
retract water
What is the major function of the large intestine
Peyer's patches
_______ protect especially distal part against bacteria; may protrude into submucosa
Duodenal (Brunner's)
______________glands of the duodenum secrete alkaline mucus to neutralize acidic chyme
definition of chemical digestion
a series of catabolic steps in which complex food molecules are broken down to their chemical building blocks by enzymes
lacteal
a thick lymph passage in the center of the villi
bile
a yellow-green, alkaline solution that emulsifies fat (reduces its surface tension) and contains bile salts and bilirubin
function of accessory organs
aid digestion physically and produce secretion to breakdown foodstuff in the GI tract
two main groups of the organs of the digestive system
alimentary canal and accessory organs
functions of the mesentery
allows blood vessels, lymphatics, and nerves to reach the digestive organs; holds the organs in place; stores fat
function of the pancreas in digestion
an accessory gland that is retroperitoneal and secretes pancreatic juice to the duodenum to assist with the digestion of proteins, carbs and fats
greater omentum
an apron of mesentery arising from the visceral peritoneum of the stomach at the greater curvature and running to cover the small intestine, the spleen and transverse LI where it attaches to the mesocolon
Peyer's patches
areas of MALT in the mucosa that extend to the submucosa
composition the submucosa
areolar connective tissue; blood and lymphatic vessels
Lingual frenulum
attachment to floor of mouth
five subdivisions of the LI
cecum, appendix, colon, rectum and anal canal
mastication
chewing - begins the mechanical breakdown of food
substance that causes the gall bladder to contract
cholecystokinin
Bile salts
cholesterol derivatives that function in fat emulsification and absorption
duct through which bile is sent to the duodenum
common hepatic duct which meets the cystic duct and forms the bile duct
What is pulp made up of?
connective tissue, blood vessels and nerves
composition of the mesentery
double layer of peritoneum that extends from the body wall to surround the digestive organs
source of bacteria in the colon and their function
enter the colon via the SI and anus and aid in the fermentation of indigestible carbs
three subdivisions of the Small Intestine
duodenum, jejunum, and the ileum
the retroperitoneal organs
duodenum, pancreas, ascending colon, descending colon, rectum
elements of the digestive process
ingestion, propulsion, mechanical digestion, chemical digestion, absorption, defecation
pharyngeal-esophageal phase of swallowing
involuntary and occurs as bolus is squeezed through the pharynx into the esophagus
section of the small intestine where most of the absorption of the GI tract occurs
jejunum
how the secretion of pancreatic juice is regulated
local hormones and the parasympathetic nervous systems
two stages of the digestive process in the mouth and esophagus
mastication and deglutition
how digestive activity is triggered
mechanical and chemical stimuli
falciform ligament
mesentery arising from the anterior abdominal wall attaching to the liver, separating the right and left lobes anteriorly and suspending the liver from the diaphragm
lesser omentum
mesentery arising from the visceral peritoneum of the liver and running to the lesser curvature of the stomach
the five different mesenteries
mesentery proper, mesocolon, greater omentum, lesser omentum, falciform ligament
composition of pancreatic juice
mostly water containing enzymes that breakdown food and electrolytes
organs of the alimentary canal
mouth, pharynx, esophagus, stomach, small intestine, large intestine
four layers of the tissue of the alimentary canal
mucosa, submucosa, muscularis externa, serosa
myenteric plexus
nerve network in the muscularis externa that is responsible for movement
retroperitoneal organs
organs that lie posterior to the mesentery on the dorsal abdominal wall
how the sole purpose of digestion differs from other organ systems
other organ systems are designed to maintain levels of substances in the blood
Bilirubin
pigment formed from heme; cholesterol, neutral fats, phospholipids and electrolytes
the deep circular folds of the mucosa and submucosa of the SI
plicae circulares
Retroperitoneal organs
posterior to peritoneum
Hepatocyte functions
process bloodborne nutrients store fat-soluble vitamins Perform detoxificaton prouce ~900ml bile per day
parietal cells function
produce hydrocloric acid HCl (to breakdown proteins) and intrinsic factor (to absorb B-12)
goblet cells function
produce mucous to protect the stomach from gastric juices and the digestive process
chief cells function
produce pepsinogen(inactive enzyme) - a proteolytic enzyme that is inactive until combined with HCl and becomes pepsin ( a positive feedback mechanism)
salivary glands' function
produce saliva which: cleans the mouth; dissolves food chemicals for taste; moistens food; compacts into bolus; begins breakdown of starch with enzymes (amylase
digestive function of the liver
produces bile
where the macronutrients are absorbed
proteins and carbs to the blood and fats to the lymph
functions of the large intestine
reabsorption of water and the elimination of indigestible materials as feces
Enterohepatic circulation
recycle bile salts
Fungiform
reddish, scattered over tongue; contain taste buds
composition and function of the esophagus
runs from the laryngopharynx to the cardiac orifice of the stomach providing a passage for food and fluids
name of the enzyme responsible for initiating the breakdown of starch
salivary amylase
function of the crypts of Lieberkühn
secretes intestinal juice that acts as a carrier fluid for the absorption of nutrients from the chyme and hormones
functions of the mucosa
secretes mucin which becomes mucus, digestive enzymes and hormones; absorbs end products of digestion (monomers)
process of chemical stimulation of the GI tract
sensors detect chemicals in the GI tract - i.e. the presence of fat, proteins, and glucose
composition of the stomach mucosa
simple columnar epithelium; Secretes two-layer coat of alkaline mucus(Basic) (>7pH) Surface layer traps bicarbonate-rich fluid beneath it Dotted with gastric pits--->gastric glands
nervous supply of the alimentary canal
supplied by enteric neurons that connect to the two plexuses of the AC; this intrinsic nervous supply is enhanced extrinsically by the parasympathetic nervous response
deglutition
swallowing - occurs in two phases: buccal and pharyngeal-esophageal phase
two elements of propulsion
swallowing, peristalsis
the accessory organs
teeth, tongue, gallbladder, salivary glands, liver, pancreas
function of the stomach
temporary storage tank for food where the chemical breakdown of proteins in initiated and food is converted to chyme
three unique features of the LI
teniae coli, haustra, epiglopic appendages
definition of ingestion
the act of putting food in your mouth
the distal, exterior opening of the GI tract
the anus
splanchnic circulation
the arterial supply of the DS branching from the abdominal aorta and the hepatic portal circulation
pyloric antrum
the broad area of the pyloric region at the base of the curvatures
the alimentary canal
the continuous muscular digestive tube that winds through the body
pylorus
the distal end of the stomach that connects to the duodenum; terminates at the pyloric valve or sphincter which controls gastric emptying
definition of defecation
the elimination of indigestible substances from the body via the anus as feces
what separates the right and left lobes of the liver
the falciform ligament (mesentery)
where bile that is not needed is stored and concentrated
the gall bladder; concentrates the bile as water leaves the GB
definition of propulsion
the motility/movement of food through the GI tract
composition and function of the pharynx
the oropharynx and laryngopharynx provide a common passageway for food, fluids and air
definition of absorption
the passage of digested end products from the lumen of the GI tract through the mucosal cells into the blood or lymph
definition of mechanical digestion
the physical process of preparing the food for chemical digestion
hepatic portal circulation
the venous portion of the splanchnic circulation carrying nutrient rich blood from the digestive organs to the liver
components of the villi
the villi of the epithelial layer of the SI mucosa contains absorptive cells and goblet cells; the lamina propria contains lacteal and dense capillary supply
composition of the serosa
the visceral peritoneum surrounding the abdominal cavity
function of the plicae circulares
to increase the surface area of the mucosa of the SI for more absorption
the sole purpose of the digestive system
to optimize digestion
Surface bears papillae
tongue
what covers the external surface of most of the digestive organs
visceral peritoneum
buccal phase of swallowing
voluntary and occurs in the mouth as bolus is forced into the oropharynx