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Home , Cystic duct, Gastric pits, Gastrointestinal tract, Jejunum, Lacteal, Mucous membrane

The Digestive System of the Digestive System We need food for cellular utilization: organs of digestive system form essentially a long !nutrients as building blocks for synthesis continuous tube open at both ends

!sugars, etc to break down for energy ! alimentary canal () most food that we eat cannot be directly used by the !!!! body !

!too large and complex to be absorbed attached to this tube are assorted accessory organs and structures that aid in the digestive processes !chemical composition must be modified to be useable by cells salivary teeth digestive system functions to altered the chemical and physical composition of food so that it can be gall bladder absorbed and used by the body; ie Functions of Digestive System: The GI tract (digestive system) is located mainly in 1. physical and chemical

2. absorption surrounded by = visceral 3. collect & eliminate nonuseable components of food this serous membrane is continuous with parietal peritoneum and extends between digestive organs as mesenteries ! hold organs in place, prevent tangling

Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 1 Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 2

is suspended from rear of soft The wall of the alimentary canal consists of 4 layers: blocks nasal passages when

outer serosa: visceral peritoneum, lines ventral border of mouth cavity mainly fibrous and areolar CT with some pockets of adipose CT is covered with

muscularis contains buds several layers of

is thin fold of mucous membrane on vessels, lymphatic vessels, , ventral surface of tongue that anchors the connective tongue to the floor of the mouth

inner mucosa: short frenulum ! “tongue tied” small band of , muscularis mucosa Teeth membrane lining two sets contains goblet cells that secrete mucous for protection deciduous (=baby teeth) (20) these layers are modified within various organs begin at 6 months; shed 6-13 yrs

! some have muscle layers well developed permanent teeth (32)

! some with mucous lining modified for each tooth has a of digestive juices

! some with mucous lining modified for absorption crown (above gum) is where crown, gum and root meet 1. Mouth (Buccal Cavity, Oral Cavity) root (below gum) bordered above by hard and imbedded in socket forms partition between mouth and nasal passages

gingivitis = of gum surrounding teeth; can lead to uvula Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 3 Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 4 periodontal disease Salivary Glands

kinds of teeth modified for specific functions 3 Pairs of salivary glands:

incisors – 4+4; cut, knip sublingual canines – 2+2; holding onto prey submandibular premolars – 4+4; cutting, crushing parotid molars – 6+6; chewing, grinding, crushing largest, below each tooth is composed of several layers: mumps = acute of parotid

secrete ( and mucous for enamel digestion) very hard outer surface 2. Pharynx (throat) on upper exposed crown only resists bacterial attack cannot regenerate if damaged already discussed

dentin 3. Esophagus

below enamel less hard, similar to matrix collapsible tube ~ 10” long decays quickly of enamel is penetrated extends from pharynx to stomach pulp !gets food through to living portion of tooth consists of blood vessels, nerves posterior to and

pierces diaphragm

on root of tooth only outer surface uses to move food to stomach holds root into socket in jaws ! can swallow upsidedown

Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 5 Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 6

drains into stomach through the cardiac orifice Muscle layers are very well developed in stomach surrounded by the lower esophageal sphincter circular longitudinal 4. Stomach oblique muscular sac just below diaphragm and liver Help to break up food by churning action alimentary canal expands to form stomach results in milky white liquid =

50 mL when empty; up to 1.5 L after meal sphincter muscles close both stomach openings:

Major functions of stomach: cardioesphageal sphincter

(=lower esophageal sphincter) 1. physical digestion – churning action heartburn !doesn’t close properly 2. chemical digestion – esp proteins pyloric sphincter

3. limited absorption (some water, , certain ) cholic in babies ! doesn’t open properly given smooth muscle relaxers divided into 4 regions: cardiac mucosal lining of stomach is folded into rugae to fundus allow for expansion with a meal body pyloris within the mucous lining of stomach are glandular tubes called cardioesophageal sphincter lesser curvature cardiac fundus !within gastric pits are numerous microscopic : pyloric sphincter body ! secrete mucous for protection greater curvature ! secretes various digestive enzymes pyloris ! secretes HCl Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 7 Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 8 central portion mostly in umbilical region 5. Small Intestine especially rich blood supply most digestion and absorption occurs here absorbs most nutrients, water & salts longest part of alimentary canal: ! 1” diameter x 10’ long (living) or 20’ long (cadaver) ~5’

mainly in hypogastric region Major functions of small intestine: joins to caecum of large intestine absorbs and reclaims salts and some additional 1. most chemical digestion of food nutrients

() mucosal lining of the small intestine is folded into

plicae 2. secretes which direct secretion of

digestive juices by stomach, gall bladder, the intestinal mucosa also contains small finger-like pancreas projections = villi

3. most absorption of digested foodstuffs ~1mm tall ( & ileum) each villus contains absorptive epithelial cells small intestine fills most of abdominal cavity and goblet cells held in place by mesenteries (=serous membranes) core of villus is filled with areolar tissue of subdivided into 3 functional regions: within this is an , bed, duodenum and ~10” long lymphatic capillary = uppermost drains pyloric stomach 6. Large Intestine receives ducts from gall bladder and pancreas

jejunum 2.5” diameter x 6’ long ~4’ Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 9 Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 10

valve-like sphincter separates small from large intestine = on the outer surface of the large intestine are 3 longitudinal bands of muscle tissue Major functions of large intestine: =

1. absorb additional water as needed by body ! muscle tone within these bands produces pouches = haustrae 2. absorb small amount of additional nutrients that allow distention

some Vit K and B’s made by in lg intestine

3. collects, concentrates and rids body of last 7-8” undigested wastes

ends at subdivided into 3 regions: held shut by two anal sphincters: of smooth muscle of skeletal muscle blind ended sac that extends from point of attachment to small intestine Intestinal Flora

contains ! ~3.5” (9cm) long our bacterial symbionts exist as a complex interacting significant source of community with specific characteristics

colon we’re finding that each person has a unique set of on their and in their guts subdivided into: the abundance of certain bacteria in your correlates with your age, gender, body mass index, and nationality our bacteria provide many benefits:

Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 11 Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 12 !help break down hard to digest fibers and starches use of can cause dramatic and long term changes in our gut flora and increase risk of some !make essential and additional nutrients chronic diseases !protect us from , toxins and some carcinogens in the future: !activate our immune systems to better resist eg. might be able to test for changes in kinds and numbers of gut bacteria change and adapt as your foods change species as an early indication of certain diseases

eg. doctors may prescribe bacterial supplements to improve ! those better able to metabolize dominant food tend to physical health increase

eg. fecal transplants: restores bowel flora to a healthy state gut bacteria affect our mood and behavior: 7. Serous Membranes correlations have been found between gut flora and some psychiatric disorders such as depression, and body wall and organs of are lined with peritoneum obesity, diabetes, Crohn’s disease, , celiac disease, all may be the !parietal peritoneum result of an imbalanced microbial ecosystem in our !visceral peritoneum guts most, but not all, of the visceral organs are completely some forms of severe malnutrition have been linked to lined with visceral peritoneum a particulary group of intestinal bacteria these layers are continuous with thin flaps of serous promising research has found that fecal transplants tissues = mesenteries have cured symptoms of Parkinsons, diabetes and obesity mesenteries allow free movement while holding organs in place and prevent them from tangling eg. 100% cure rate for C. difficile infections, a deadly disease common in patients on therapy

fold of extending from stomach and

Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 13 Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 14

duodenum blood leaving the liver enters the Hepatic to the loosely covers the small intestine like an apron Vena Cava

contains deposits bile leaves the liver through the Hepatic Bile lesser omentum B. Gall Bladder

smaller fold of mesentery between liver and lies on undersurface of liver stomach 3-4” long and 1.5” wide

liver produces 0.6 – 1.2L of bile/day Accessory Organs of Digestive Tract bile travels up to gall bladder for A. Liver storage

is the largest gland in body can hold 30-50 ml of bile

gall bladder stores and concentrates bile lies immediately under the diaphragm

When needed bile travels down Cystic Duct to consist of 2 lobes separated by falciform Common to the duodenum ligament C. Pancreas receives blood from the Hepatic and the Hepatic Portal Vein most digestion is carried out by pancreatic enzymes

in curve of duodenum and dorsal to greater Hepatic Artery Hepatic Vein curvature of the stomach (retroperitoneal) Liver Hepatic Portal Hepatic Bile Duct 6-9 “ long Vein

Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 15 Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 16 composed of 2 kinds of glandular tissue: Digestive Physiology

endocrine ! secretes hormones Muscular Movements (=) in GI Tract

islets = 2% of total mass of pancreas as materials are being processed they are moved their pass into through alimentary canal by by several muscular secrete and glucagon processes:

exocrine ! digestive function chewing voluntary movements of skeletal muscles pancreatic digestive secretions average ~2L/day swallowing ! mainly on demand, in short timespans coordinated activity of skeletal and smooth muscles reflex controlled by medulla pancreatic secretions are collected in pharynx to esophagus and usually a smaller accessory pancreatic duct that both drain into the duodenum peristalsis propulsive movements sequential smooth muscle contractions in adjacent segments !pushes food forward esophagus, stomach, small intestine, large intestine

segmentation mixing movements alternating contractions and relaxations of adjoining portions of intestine food is moved backward and foreward !helps to physically break up and mix contents for better digestion & absorption

mass movements occur 1-3 times/day when all circular muscle constricts in a long stretch of intestine to push food toward anus ! main propulsive force in large intestine

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sphincters 2. Pharynx tonic contractions of smooth and skeletal muscles that control the emptying and filling of various portions of is swallowed the GI tract uvula closes off nares Digestion closes off glottis of digestion = all food changes that occur in the 3. Esophagus alimentary canal wave of reflex contractions = peristalsis need to convert food into a form that can be absorbed and used by body cells 4. Stomach two types of digestion: muscular contractions separate and mix food particles and move them toward the physical digestion breaking large pieces down into smaller pieces in stomach bolus is mixed with gastric juices gastric juices low pH ~2 chemical digestion breaking large molecules (proteins, , starches, etc) ! ideal for breaking proteins into into small molecules smaller fragments (amino acids, fatty acids, sugars, etc) gastric ulcers: pylori 1. Mouth part of normal flora of stomach can neutralize stomach acids excessive growth can irritate stomach lining to produce food entering mouth is physically broken down ulcers teeth mixed with saliva physical digestion is completed in stomach lubricant = once digestion in stomach is competed have a ! begins digestion white milky liquid = chyme

at end of digestion in mouth, food = bolus stomach takes about 2-6 hours to empty after a meal

Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 19 Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 20 gastric emptying is controlled by enterogastric reflex: hard masses of , calcium carbonate & periodic opening/ closing of pyloric valve bilirubin prevents overburdening smaller duodenum may block cystic duct 5. Duodenum jaundice = bile ducts obstructed all physical digestion has been completed !body cant get rid of bile !bile is absorbed into blood !causes yellowing of skin !most chemical digestion occurs here droplets to speed their digestion receives digestive juices from pancreas and gall bladder 95% of bile secreted by gall bladder is reabsorbed after it is used in digestion also produces its own set of enzymes ! recycled back to liver a. Bile fiber inhibits reabsorption or bile

bile contains no enzymes ! fiber rich diets help to lower cholesterol

does contain bile salts, cholesterol and b. Pancreatic Juices other lipids pancreas is an (insulin, most lipids are very insoluble in water glucagon)

! must be made somewhat soluble before but 98% of its tissues make and secrete they can be digested and absorbed digestive juices through ducts to the duodenum bile is a surfactant c. Duodenal Secretions ! emulsifies fats into smaller fat

gall stones Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 21 Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 22

secrete additional enzymes that help to Absorption complete the breakdown of organic molecules ~9-10 liters (2.5 gallons) of food, liquids and GI secretions enter tract/day peristaltic movements keep the food moving along the small intestine as it is digested and ~1000 ml reaches the large intestine nutrients are absorbed 150 ml is expelled as feces 6. Large Intestine ~half of that is bacteria from intestines contains a mixture of remnants of several meals eaten over a day or two ! 75 ml wastes/d

food is mixed and compacted by segmentation absorption occurs throughout digestive tract

peristaltic contractions propel food toward anus ~90% occurs in small intestine

mass movements occur 1-3 times/day when all ~10% in large intestine and stomach circular muscle constricts in a long stretch of intestine to push food toward anus Stomach ! main propulsive force in large intestine some water alcohol some digestion occurs here due to bacteria a few drugs (eg. aspirin) !esp in caecum Small Intestine absorb ~90% of materials as feces enters rectum, stretch receptors trigger absorbs virtually all foodstuffs the awareness of need for absorbs 80% of absorbs most water defecation proceeds by coordinated activity of Jejunum smooth and skeletal muscles in the all food stuffs defecation reflex most water most electrolytes Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 23 Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 24 Large Intestine Ileum reclaims some additional bile salts additional water if body needs it

Small intestine is greatly modified for absorption some Vit K and B’s made by bacteria there

1. epithelial cells are joined by tight Mechanisms of Absorption junctions absorption can be an active or passive process: better control of what is absorbed substances cant move between cells 1. most nutrients are absorbed by materials must pass through cells to get to interstitial spaces eg. (=transepithelial transport) amino acids some minerals 2. surface area is greatly increased for more efficient absorption of nutrients: 2. water is absorbed by osmosis

1” diameter x 10’ long ! if smooth tube = 0.33 m2 (3 sq ft) 3. large molecules are absorbed by pinocytosis

but: interior is folded eg. a few large fats and proteins; fats passed to ! increases area ~3 x’s with other fats

also: fingerlike projections = villi 4. some lipids are absorbed by diffusion to lacteals ~1mm tall contain capillary beds Feces = “residue of digestion” contain lacteals

! increases area another 10x’s cellulose connective tissues, fibers, toxins from meats also: each epithelial cell of villus has microvilli undigested fats and mucous up to 1700/cell =brush border bacteria (~50%) ! increases area another 20x’s feces may also contain recognizable remnants of poorly digested foods: corn, peanuts, peas, carrots, cereals, 2 Total Area = 200m (1800 sq ft) beans

Liver Processing Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 25 Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 26

Liver Lobule the liver is main for metabolic regulation in the body lobule is functional unit of liver

! over 200 specific functions !each liver lobe is divided into 1000’s of lobules 1. stores , A, B12 & D tiny hexagonal cylinders (~2mm x 1mm) 2. helps stabilize blood glucose levels by storing excess glucose or synthesizing glucose if ~ 1 million lobules in human liver

needed small branches of hepatic vein extend through middle of each lobule as central vein 3. carries out most of body’s fat synthesis sinusoid spaces lined with hepatic cells extend outward including cholesterol and phospholipids from central vein

4. synthesizes plasma proteins & degrades around periphery of each lobule are branches of excess amino acids hepatic portal vein hepatic artery hepatic bile ducts 5. phagocytes remove old/damaged blood cells and pathogens ! arterial blood brings to liver cells

6. detoxify blood from digestive system ! from hepatic portal vein delivers removes drugs, alcohol, antibiotics, etc blood through lobule for “inspection”:

7. is largest blood reservoir in body a. phagocytic cells remove toxic compounds and convert them to nontoxic compounds receives 25% of b. some vitamins and nutrients are removed and stored 8. collects and removes metabolic wastes such as cholesterol, products of RBC destruction, etc c. synthesis of starches, lipids and proteins for storage

! cholesterol, bile pigments and bile salts are 9. secrete bile to aid in digestion (~1pt /day) secreted

Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 27 Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 28 into bile ducts for later use in digestion of fats The Aging Digestive System hepatic bile ducts join cystic duct ! store bile in shows significant senescence in old age: gall bladder less saliva sinusoids ! food less flavorful, harder swallowing Hepatic Artery Hepatic Vein oxygen ~half of those over 65 yrs wear dentures removes toxins Hepatic Portal Hepatic Bile Ducts Vein stores vitamins secretes less acid

stores nutrients Hepatic Duct ! reduces absorption of Calcium iron, and folic acid

gastric mucosa secretes less

Cystic Duct ! reduces absorption of ! leads to pernicious Heartburn becomes more common

most common digestive complaint of older people is

!due to: less muscle tone weaker colon peristalsis reduced sensitivity to neurotransmitters less fiber & water in diet less exercise

activity of liver, gall bladder and pancreas are reduced only slightly in old age

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Digestive Problems Colonic Irrigation alternative medical practice 1. Choking potentially harmful food in air passages unneccessary usually meats, hot dogs, grapes, carrots, hard can rupture the intestine candy, popcorn, peanut butter may not be able to make a sound frequent use of and : DON’T hit on back can lead to dependency upset body’s fluid balance 2. symptom of many diseases can interfere with absorption of fat soluble vitamins waves of reverse peristalsis

if severe may empty duodenum as well rest and drink small amounts of fluids 6. Belching guard against massive fluid loss results from swallowed air carbonated drinks and chewing can 3. Bulemia contribute occasionally can be a sign of a more serious self induced vomiting disorder: gall bladder pain, colonic distress may cause damage and infection of esophagus, eat slowly, chew thoroughly pharynx, or salivary glands relax while erosion of teeth, more dental caries

esophagus may rupture or tear 7. Hiccups 4. repeated spasms of diaphragm may be triggered by eating or drinking too fast frequent loose watery stool

intestinal contents moving too fast for fluid absorption to occur 8. Gas main danger is fluid loss large intestine generates 7-10 L of gas/day and also upsets acid/base balance normally we expel ~500ml of gas/day the rest is reabsorbed 5. Constipation most is odorless 1% are “volatile” gasses caused by: high carb foods known to produce excess gas lifestyle ! inadequate water input

lack of physical activity side effect of 9. Heartburn (& gastroesophageal reflux disease) controlled by increase in fiber, prunes, laxatives cardiac sphincter doesn’t close properly ! attracts water ! softens stool affects 50% of US, esp white males

Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 31 Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 32 eat or drink too much clothing too tight 12. Pica cure: eat small meals the compulsion to swallow nonfood items drink liquids 1 hr before or 1 hr after meal don’t lie down or bend over pica behavior is normal for lose weight if overweight !they explore their world through their mouth’s don’t smoke use but sparingly in adults it could become dangerous or even life threatening

10. Ulcers eg. pregnant women - rich smell of soil drove them to eat it a lesion of stomach or duodenum caused by acids or ! duodenal ulcers are the most common eg. another pregnant woman was eating almost half a kg of perforated extend through entire wall of GI tract baking soda each day caused by: bacterial infection, , is important cause of eg. compulsive consumption of ice is often associated with iron most ulcers deficiency !in all patients with duodenal ulcers !in 80% of patients with gastric ulcers eg. 9 year old girl routinely ate cloth an string was helped by probably disrupt mucosal barrier taking vitamin supplements use of some antiinflammatory drugs disorders that cause excessive gastric secretions eg. soil eating is common in many traditional societies reduced mucosal defense ! may be instinctive way to get trace minerals like Fe or Zn diet therapy used to be main cure, now antibiotics also advised to stop and avoid alcohol and caffeine pica is also common among people with cognitive or psychiatric disorders such as autism and schizophrenia 11. Celiac Disease eg. a compulsion to eat cigarette lighters or $650 worth of chronic disorder in which the mucosa of small intestine is coins damaged by ingestio fo certain cereal grains, eg. wheat, barley, rye, & oats disease 1st reported in second century by Aretaeus of Gall Stones Cappadochia these grains have large amounts of a , =gluten, “calculi” can form in , and causes loss of villi & brush border, and increased numbers of WBC’s gall bladder leads to inadequate intestinal absorption symptoms: diarrhea, weight loss, and seed becomes surrounded by layers of crystalline and weakness due to genetic and environmental factors deposits patients with such sensitivity must adhere to gluten-free diet substitute: corn, millet, buckwheat, sorghum & rice if large enough can block cystic duct or common Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 33 Human Anatomy & Physiology: Digestive System; Ziser Lecture Notes, 2014.4 34

bile duct and cause jaundice

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