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