Digestive

Digestive System

Anatomy

Physiology

Alimentary Canal (Gastrointestinal (GI) tract)

Accessory

Teeth

Tongue

Gallbladder

Digestive Glands

Salivary Glands

Liver

Pancreas

Digestive

Ingestion

Propulsion

Mechanical Breakdown

Digestion

Absorption

Defecation

Eating

Moving of food through alimentary canal

Swallowing

Peristalsis

Propulsion of food involving alternating waves of contraction and relaxation

Chewing, mixing foods with saliva by the tongue, churning of food in stomach, segmentation.

Segmentation

rhythmic local contractions of the small intestine that mixes food with digestive juices; also efficient absorption

series of catabolic steps that involves enzymes breaking down complex food molecules into chemical building blocks

Passage of digested end products from lumen of GI tract into blood or lymph

vitamins, minerals, and water

elimination. of indigestible substances via anus in. form. of feces

Abdominal Cavity

Peritoneum

Visceral

Parietal

membrane on external surface of most digestive organs

membrane that lines body wall

Peritoneal Cavity

contains serous fluid which allows mobility of digestive organs to glide across each other against body wall

Mesentary

Intraperitoneal Organs

Stomach, most of small intestine and parts of large intestine

Retroperitoneal Organs

Pancreas, Duodenum, and parts of large intestine

Functions

holds organs in place and also stores fat

provides routes for blood vessels, lymphatic and nerves

double layer of peritoneum

extends from body wall to digestive organs

Mesentaries

Greater Omentum

Lesser Omentum

Falciform Ligament

Mesentary Proper

Mesocolon

Secures parts of large intestine to posterior abdominal wall

Suspends most of small intestine from posterior abdominal wall

drapes inferiorly. from the greater curvature of the stomach

liver to the lesser curvature of the stomach

suspends liver from diaphragm and anterior abdominal wall

Organs

Small Intestine

Esophagus

Mouth (Oral (Buccal) Cavity)

Pharynx

Stomach

Anus

Histology of Alimentary Canal

Layers

Mucosa

Submucosa

Muscularis

Serosa

Characteristics

Functions

Secretion, Absorption, Protect against infection

innermost layer of lumen

Simple Columnar Epithelium

In mouth, esophagus, and anus

stratified squamous epithelium

MALT

Characterisics

consists of areolar connective tissue

contains blood and lymphatic vessels

Abundant elastic tissues that help organs to regain shape after storing large meal

Characteristics

smooth muscle layer for segmentation and peristalsis

inner circular muscle layer and outer longitudinal layers

contains sphincters

Characteristics

outermost layer

replaced by adventitia in esophagus

dense. connective tissue

Functions

Ingests

mechanical breakdown by chewing

initiates propulsion by swallowing

starts the digestion of polysaccharides

Characteristics

Palate

Tongue

Filiform Papillae

Forms roof of mouth

Hard Palate

Soft Palate

mucosa is to help create friction against tongue

closes off nasopharynx during swallowing with help of downward projecting uvula

Functions

Gripping, repositioning, and mixing food during chewing

Forms Bolus: mixture of food and saliva

initiates swallowing and aids in speech and sense of taste

Gives tongue roughness to provide friction: only one that does not contain taste buds, gives tongue a whitish appearance

Saliva

Minor (Intrinsic) Glands

Major (extrinsic) Glands

Secretory Cells

Parotid

Submandibular

Sublingual

Serous Cells

Mucous Cells

Functions

initiates swallowing and aids in speech and sense of taste

Gripping, repositioning, and mixing food during chewing

Forms Bolus: mixture of food and saliva

Functions

Allows passage of food, fluids and air

Stratified squamous epithelium lining with mucus-producing glands

functions

is flat muscular tube that runs from laryngopharynx to stomach.

is collapsed when not involved in food propulsion

temporary storage tank that starts chemical breakdown of protein digestion.

converts bolus of food to paste-like chyme

Anatomy

Gastric Gland Cells

Parietal Cells

Chief Cells

Enteroendocrine

Secrete Hydrochloric acid

denatures protein, activates pepsin, breaks down plant cell walls & kills many bacteria

secrete pepsinogen

inactive enzyme that is activated by pepsin by hydrochloric acid & by pepsin itself

secrete chemical messengers some paracrines while others are hormones

Mucosal Barrier

protects stomach from harsh conditions & is created by 3 factors

Thick layer of bicarbonate- rich mucus

Digestive Process

Serves as holding area for food

Propulsion

mechanical breakdown

digestion

absorption

intrinsic factor

required intestial absorption of vitamin b12

B12 needed for RBC to mature

Lack of intrinsic factor causes pernicious anemia

treated with B12 injections or nasal gel

Gastric Secretion

Cephalic (reflex) phase

Gastric Phase

Triggered by aroma, taste, sight and thought

stimulate gastric glands

inhibited by loss of appetite and depression

stimulated by distension, peptides, and low acidity

activates stretch receptors, initiating both long. and short reflexes

Partially digested proteins activate enteroendocrine G cells to secrete gastrin

Release of gastrin initiates HCL release from parietal cells

binds to receptors on parietal cells

stimulates eneteroendocrine cells to release histamine

inhibited by excessive acidity in stomach & emotional stress

Low pH inhibits gastrin secretion

stress, fear, etc

Intestinal Phase

stimulated by partially digested food in small intestine

causes small release of intestinal gastrin

inhibited by duodenum of

distension or presence of acidic, fatty , or hypertonic chyme

enterogastric reflex

duodenum inhibits. acid secretion in stomach by short and long reflexes

enterogastrones

duodenal enteroendocrine cells release 2 important hormones that inhibit gastric secretion

secretin

cholecystokinin

Regulation of Gastric Motility & Emptying

Filling

Stretches to accommodate incoming food

Gastric contractile activity (gastric mixing)

Gastric Emptying

enteric pacemaker cells

distension and gastrin increase force of contraction

duodenum can prevent overfilling by. controlling the amount of chyme enters

digestive function is production of bile

Anatomy

4 primary lobes

Falciform ligament

round ligament

blood enters through hepatic artery and hepatic portal vein and enter liver at porta hepatis

Liver Lobules

Portal Triad

Liver Sinusoids

Stellate macrophages

Hepatocytes filter and process nutrient- rich blood

Central vein

hepatic artery supplies oxygen

hepatic portal vein brings nutrient rich blood from intestines

Bile duct receives bile from bile canaliculi

blood from hepatic portal vein & hepatic artery proper goes through sinusoids and empties into central vein

in liver sinusoids and remove debris and old RBC's

Bile

Bile salts

Bilirubin

cholestrol

function in fat emulsification and absorption

pigment from heme

broken down by bacteria in intestine to stercobilin

Functions

store and concentrate bile by absorbing water & ions

contractions of muscle release bile through cystic duct then flows into bile duct

Functions

Exocrine

Endocrine

secrete pancreatic juice through duct

Acini contains secretory cells that produce zymogen granules that contain proenzymes

secretion of insulin and glucagon by pancreatic islet cells

Composed of watery alkaline solution

elcetrolytes

Proteases (trypsin)

Amylase (carbohydrates)

Lipases (lipids)

Nucleases (nucleic acids)

Large Intestine

Characteristics

Major organ of digestion and absorption

Duodenum

Jejunum

Ileum

circular folds

villi

microvilli

Histology

Function

modifications of mucosa and submucosa reflect function in digestion

Intestinal crypts

Cells

Enterocytes

Tubular glands scattered between villi

Goblet Cells

Enteroendocrine

Paneth

absorb nutrients and elctrocytes and produce intestinal juice

mucus-secreting cells

source of enterogastrones

secrete antimicrobial agents

Peyers patches

Duodenal glands

Characteristics

Teniae Coli

Haustra

Cecum

Appendix

Colon

Rectum

Anal Canal

MALT

Ascending, Transverse, Descending

Sigmoid

Rectal valves

Contains thicker mucosa

Simple Columnar epithelium, except anal canal carries stratified squamous epithelium

Digestive Process

Residue remains in large intestine 12-24 hrs

Motility of large intestine

Mass movements

Defecation Reflex

Digestive Process

Chyme from stomach has partially digested carbohydrates, proteins and undigested fats 3-6 hrs

Sources of enzymes fro digestion such as bile, bicarbonate, digestive enzymes

Regulating chyme entry has to be slow to prevent osmotic loss of water from blood

Motility of small intestine mechanical breakdown, propulsion

Ileocecal valve control opens and enter chyme to large intestine

Intrinsic & accessory gland enzymes are involved in digestion

enzymes carry out hydrolysis

tight junctions ensure molecules pass through epithelial cell and not pass through between

most nutrients are absorbed by active transport processes driven by ATP

Carbohydrates

only monosaccharides can be absorbed

starch and disaccharides are broken down to oligosaccharides & disaccharides through salivary amylase

broken down into lactose, maltose and sucrose

final broken into glucose, fructose, galactose

Proteins

Large polypeptides

Small polypeptides & small peptides

Amino acid monomers

pepsinogen converted to pepsin

pancreatic proteases

brush border enzymes

cleave protein into smaller peptides

break oligopeptides & dipeptides into amino acids

Lipids

Emulsification

Digestion

Pancreatic lipases

fatty acids

monoglycerides

Micelle formation

Diffusion

Nucleic Acids

pancreatic nucleases

nucleotide monomers

brush border enzymes

Vitamins

Small intestine

Large intestine

Fat soluble vitamins A, D, E, K

Water soluble vitamins C, B

Vitamins K and B

removal of gall bladder also known as cholecystectomy.

when using of a feeding tube solids need to be blended to liquid to enter into the tube

Gallbladder stores bile and removal of gallbladder would be due to gallstones or other problems associated with the gallbladder such as infection , etc

stomach cancer in most causes develop mutation of DNA and grows rapidly and spreads which eventually will lead to cancer cells and then formation of a tumor

symptoms of stomach cancer

fatugue

heartburn

stomach pain

continuously vomiting

severe indigestant

Inmost stomach cancers patients do get a feeding tube inserted for the purpose of maintaining their diet and health,

the feeding tube also does help bypass any other implications that may worsen with the cancer

treatments for cancer include radiotherapy and chemotherapy which target cancer cells

this also targets rapidly dividing GI tract epithelium

lack of motility of intestines is common in elderly patients this affects the movement of bile and other items to move in the gastrointestinal tract

elderly patients most likely would need to be monitored frequently especially when taking their meal.

most preparations need to be recommended through the doctor such as food that might cause acid reflex or stomach pains such as spicy food may not be allowed.

even medications and vitamins are taken through the tube in liquid form in order to stay healthy

most foods, liquids will be in tube feeding formula. but not medications.

it is important to keep the tube clean as it may cause bacteria to stay inside the tube which can cause the patient to become sick.

to efficiently keep the tube clean is to ensure before and after meals to insert warm water to get rid of any bacteria or leftover liquids.

in some cases the tube can get blocked if formula or liquid is too thick but this can be easily taken care of by using warm water or calling the patients doctor.

without the gallbladder there will be no storage for the bile it passes on to the liver which will then release into small intestine, making it possible for food to be received and flow towards the rectum

Nervous system Control

Intrinsic controls

Extrinsic Controls

Short Reflexes

Long reflexes

occur entirely within the gastrointestinal wall

involve the CNS