Chapter 23 Digestive System Flashcards
1
Q
Digestive System
A
- Two groups of organs
- Alimentary Canal (Gastrointestinal GI tract)
- mouth to anus
- digests food/ absorbs fragments
- Mouth, pharynx, esophagous, stomach, small intestine, large intesitn
- Accesory Digestive organs
- Teeth, tounge, gallbladder, digestive glands
2
Q
Digestive Processes
A
- Ingestion) taking food into digestive tract (eating)
- Propulsion) moves food through alimentary canal
- swallowing) Initated voluntary
- periatalsis) Involuntary swallowing
- Mechanincal breakdown) chewing, mixing food with saliva, churning
- Segmentation) local constrictions of small intestine to mix food with digestive juices. makes absorption more efficent.
- Digestion) Catabolic reation where enzymes secreted into lumen brak down food
- Absorption) Passage of Digested end products from the lumen of GI tract into blood
- Defication) elimination of indesgtibale substances from the body
3
Q
Peritonium and Peritoneal Cavity
A
- Peritoneum) serous membrane of abdominal cavity
- Visceral Peritoneum) on external surface of most digestive organs
- Parietal Peritoneum) lines the body wall
- Peritoneal cavity) between two peritoneums
- fluid lubricates mobile organs
- Mesentary) Duble layer of peritoneusm
- sheet of two membranes fused back to back
- extends to digestive organs from the body wall
- Routes vesels and nerves to digestive organs
- Holds organs in place. Stores fat
- Mostly found dorsally, some ventral mesentary
- Retroperitoneal Organs) Posterior to peritoneum
- most of the pancreas and duodenum and parts of large intestine
- Intraperitoneal Organs) Surrounded by peritoneum
- Stomach keeps its mesentary
4
Q
Peritonitis
A
- Inflammation of the peritoneum
- causes) piercing abdominal wound, ulcer, ruptured apendix
- Treatment) removal of debris and antibiotice
5
Q
Histology of the Alimentary Canal) Mucosa
A
- Mucosa) moist epithelial membrane that lines alimentary canal lumen from mouth to anus
- Secretes mucus, digestive enzymes and hormones
- Absorbs end products of digestion
- Protects against infectious desiese
- Three Sublayers
- Epithelium) Simple columnar epitheliam rich in mucus- secreting cells
- stratified squamous epithelium in mouth, esophagous, and anus
- Mucus) Protects digestive organs from enzymes and eases food passage
- Lamina Propria) Loose areolar connective tissue
- Capalries nurish epithelium and absorb digestion nutrients
- Lymphoid Follicles) defend against microoorganisms
- Muscularis Muscosae) Layer of smooth muscle cell
- provide local movemnts of mucosa
6
Q
Histology of the Alimentary Canal) Submucosa
A
- Areolar connective tissue
- Blood and lymphatic vessels, lymphoid follicles and nerve plexus.
- Abundent elastic fibers enable stomach to regain its normal shape after temporarily storing a large meal
7
Q
Histology of the Alimentary Canal) Muscularis Externa
A
- Responsible for Segmentation and Peristalsis
- Inner circular and outer longitudinal layers
- Sphincters) circular layer thickents in some areas
- Myenteric nerve plexis located bettween two muscle layers
8
Q
Serosa
A
- Outermoast layer of intraperitonal organs is Visceral Peritoium
- Areolar CT covered with moesothelium (single layer of squamous epithelial cells)
- Serosa is replaced by fibrous dense, CT called Adventitia in esophagus
- Retropreitoneal Organs) have both an adventitia and serosa
- adventita) faces dorsal body wall
- Serosa) faces peritoneal cavity
*
9
Q
Blood Supply) Splanchic Circulation
A
- Splanchnic Circulation) arteries that branch off abdominal aorta to serve digestive organs and hepatic portal circulation
- Aterial suply the branches of celiac trunk that serve spleen liver and stomach and the mesentaric aterties which serve digestive system (recive one quarter of cardiac output)
- Hepatic Portal Circulation
- Drains nutrient-rich blood from digestive organs
- Delivers to Liver for processing
10
Q
Enteric Nervous System
A
- Entric Nervous System) GI trac’ts own nervous system
- conists of over 100 million nuerons
- Steffed by enteric nuersons
- Two major Intresnsic Nervous Plexuses (ganglia ocnnected via unmyelnated tracts) found in the wall of the GI canal
- Submucosal Nerve Plexus) occupies submucosa
- Myerntric Nerve Plexus) lies between circular and longitudal mucle laters of muscularis externa
- Myenteric = Intestinal Muscle
- Entrict Neuerons control GI tract mobility
- Short Reflex arcs) Respond to stimuli inside GI tract
- controls segmentation and peristalsis
- involves pacemaker cells
- “Gut Brain” ) local intresnsic nerve plexus
- Long Reflex Arcs) Responds to stimuli inside or outside the GI tract
- Involve CNS centers and autnomic nerves
11
Q
Concepts of Regulating Digestive Activity
A
- Provoked by a range of mechanical and chemical stimuli
- Receptors are in wall of GI tract organs
- Reponds to stretch, changes in osmolality and ph, presense of substrate and end products of digestion
- Effectors of Digestive activity are smooth muscle and glands
- Initate reflexes
- Activate/ inhibit digestive glands
- stimulate smooth muscle to mix and move lumen contents
- Nuerons. (intrinsic and extrinsic) and hormones control activity
- Nuerons) control digestive system intresnsicly and extrensically
- Hormones) from cells in stomach/ small intestine stimulare tatget cells or organs
12
Q
Mouth
A
- Oral (buccal) cavity
- bounded by lips, cheeks, palate and tounge
- Lined with statified squamous epithelium
- Lips and Cheeks
- Contain obicularic oris and buccinator muscles
- Vestible (“Porch”) space betwen gums and lip
- Oral cavity proper) area within teeth and gums
- Labial Frenulum) median attachment of each lip to the gum
13
Q
Palate
A
- Hard Palate) Palatine bones and palatine process of maxillae
- forms a ridgid surface which the tounge forces food agaisnt while chewing
- Raphe) midlle rigdge which is slightly corrugated
- Soft Palate) fold formed mostly of skeletal muscle
- closes nasopharynx when swallowing
- Uvula projects downward from its free edge
14
Q
Tounge
A
- Skeletal Mucslce; Functions Include
- Repositioning/ mixing food during chewing
- Formation of bolus
- Initation of swallowing, speech and taste
- Intresnic Muscles) change shape of tounge as needed
- Extrensic muscles) change tounges position
- Lingual frenulum) attachemnt to the floor
- Papillae) holds tate buds
- Filifrom) whitish, give tounge rougness and provide friction
- Fungiform) reddish, scattered over tounge, contain taste buds
- Circumvallate (vallate) v shaped row on back of tounge; contains buds
- Folitate) on lateral aspects of the tounge
15
Q
Salivary Glands
A
- Extrinsic Salivary Glands) PRiduce saliva; lie outside oral cavity
- Partoid, Sumbandibular, Sublingual
- Minor/ Intresnsic Salivary glands) scattered throuought oral cavuty
- Buccal glands and others
- Function of Saliva
- cleans mouth, dissolves food chemicals for tatste, moistens food, and begins to break down starch via enzyme amylase
- Partoid Gland) major salivary glands
- anterior to ear; ecternal to masseter mucle
- Duct opens itno vestible next to second upper molar
- Submandibular
- Medial to body of mandible
- Duct opens at base of lungual frenulum
- Sublingual Gland
- Anterior to submandibular gland under tounge
- Opens via 10-20 ducts into floor of the mouts
- Two typed of silvary gland cell secretions
- Serous cells) watery, enxymes, ions, bit of mucin
- Mucous cells) mucus
- 97-99.5 percent water, slightly acidic
- 1500 ml/day
16
Q
Teeth
A
- Tear and grind food for digestion
- fully formed by age 21
- 20 Decidous teeth (decid = falling off)
- baby teeth
- Roots reabsorb when teeth fall out
- 32 Permanent Teeth
- All but third molars in by end of adolescense
- third molars ( widsom teeth) may or may not erupt
- Incisors) chisel shaped for cutting
- Canines) fang like teeth that tear or pierce
- Premolars (bicuspids) Broad corwn, Rounded cusps- grind/grush
- Molars) Broad corwn, Rounded cusps - best grinders
17
Q
Tooth Structure
A
- Crown) exposed part above gingiva (gum)
- covered by enamal (hardest substance in body)
- Enamal-producing cells degenrate when tooth erupts
- Root) Portion embed in jawbone
- Cement) calcified connective tissue
- Peridontal Ligament) Anchors tooth in bony socket
- Gomphosis) tooth joint
- Ginvival sulcus) groove where gums boarders tooth
- Dentin) bonelike material under enamal
- Pulp cavity) surrounded by dentin, Contains pult
- Root canal) where pulp cavity extends to root
- Apical Foramen) at proximal end of the root
18
Q
Tooth and Gum Disease
A
- Dental Caries (rottenness)(cavities) demineralization of enamal and entin from bacterial action
- dental plaque) adheres to teeth
- acid from bacteria dissolvles calcium salts
- Enzymes from bacteria digest organic matter
- Gingivits) plaque calcifies to from calculus (tarter)
- Calculus dirupts seal between gingicae and teeth
- Anerobic bacteria infects gums
- Peridontitis or Periodontal Disease (neglected gingivitis)
- Immune cells destroy peridontal ligament and dissolve bone
- Possible tooth loss
19
Q
Digestive Processes) Mouth
A
- Ingestion (eating)
- Mechanical Digestion (Mastication) (chewing)
- Cheeks and closed lips hold food between teeth
- Tounge mixes food with saliva; compacts food into bolus
- teeth cut and grind
- Propulsion (Deglutition or swallowing)
- Chemical digestion) salivary amulase and lingual lipase
- some drugs can be absorbed into mouth
20
Q
Pharynx
A
- Food passes from mouth > oropharynx > laryngopharynx
- Allows passage of food and air
- Statified squamous eitheliam
- Pharyngeal Constrictors) encircle the wall
21
Q
Esophagus
A
- Flat muscular tube from laryngopharynx to stomach
- Pierces diaphragm at esophageal hiatus
- Joins stomach at cardial oriface
- Gastrophageal (cardiac) sphincter) surrounds cardial orifice
- Esophegial mucosa
- Contains stratified squamous epithelium
- changes to simple columar at the stomach
- Esophageal glands in submucosa) secrete mucus to aid in bolus movment
- Adventiti is CT
22
Q
Deglutition (swallowing)
A
- Involves tounge, soft palate, pharynx, and esophagus
- 22 muscle groups help with swallowing
- Buccal Phase
- Occurs in mouth, is voluntary ends when food leaves the mouth
- Pharyngeal-esophageal pase
- Involuntary- primarrly vagus nerervr
- Controlled by swalllowing center in the medulla and pons
- Once food enters the pharynxm respiration momnetarily inhibited
- Solid food passes from oropgaynx to the stomach.
23
Q
Stomach) Gross anatomy
A
- Upper left Quadrant is Temporary storage
- chemical digestion of Bolus. Changes to Chyme
- Rugae) When empty; stomcach collapses inward and mucosa and submucosa wrinkle into large, longutidinal folds called Rugae
- Cardia) near the heart
- surrounds cardial oriface where food enters
- Fundus) dome shaped region beneath diaphragm
- Body) midportion
- Pyloric Part) Inferior part of stomach
- Plyoric Antrum) superior portion, leads into Plyoric canal
- Continuious with duodenum through the plyoric valvue (Sphincter).
- Greater Curvature) Convex Lateral Surface
- Lesser Curvature) concave medial surface
- Two messentaries, called Omenta anchor the stomach
- Lesser Omentum) Liver to lesser curvature
- Greater omentum) drapes inferiorly from greater curvature > over large intestine > attaches to spleen and transcerse colon (transverse mesocolon)
- Innervation
- Sympatetic) Thoracic splabchnic nerves through celiac ganglion
- Parasympatic) vagus nerve
- Blood Supply
- Cliac Trunk) gastric and splenic branches
- Veins) Hepatic Portal system
24
Q
Stomach) Microscopic Anatomy
A
- Contains normal Tunics of Alamanery canal (Mucosa, Submucosa, Muscularis Externa, Serosa) but the Mucosa and Muscularis Externa are diffrent
- Muscularis Externa
- Three layers of smooth muscle instead of two
- Circular, longitudal, and innermost oblique layer
- Allows stomach to churn, move, and mix food
- Mucosa
- Simple columnar epithelium compsoed of mucous cells
- Secrete two layer coat of Alkaline mucus
- surface layer) traps bicarbonate-rich fluid beneath it
- Contains Gastric Pits that Lead into Gastric Glands
25
Q
Gastic Glands
A
- Produce Gastric Juice
- Cell types
- mucus neck cells, Parietal cells, chief cells, entroendocrine cells
- Glands in fundus and body produce most of the stomach secretions
- Prietal Cell Secretions
- Hydrochloric Acid (HCl) pH 1.5-3.5. Denatures protein, activates pepsin, breaks down plant cell walls, kills bacetia
- Intrensic factor) glycoproteinen required for B12 absorption
- Cheif cell secretions
- Pepsinogen) Inactive form of pepsin activted by HCl and peprsin itself
- Lipases) digest about 15% of lipids
- Enteroendocrine cells (“gut endocrine”)
- secrete chemical messengers
- Act as paracrines (seratonin and histamine)
- Somatostatin Hormone) acts as a paracrine
- Gastrin Hormone) regulates stomach secretion and mobility.
26
Q
Mucosal Barrier
A
- Harsh digestive enzymes can digest stomach itself but it has mucosal barrier to protect itself
- three factors
- Thick layer of bicarbonate-rich mucus
- Tight Junctions between epithelial cells
- prevents juice from seeping into tissue
- Damaged epithelial cells quickly replaced by division of stem cells.
- Surface cells replaced every 3-6 days
27
Q
Gastritis
A
- Inflammation caused by anything that breaches mucosal barrier
- Persistent damage to undelying tissues can cause
- peptic ulcers, specifically called gastric ulcers when it is stomach wall is eroding. Cause Hemmorage
- Caused mostly by Helicobacter Pylori Bacteria,
- NSAID’s, smoking, spicy food, alcohol, coffee or stress also can cuase.
28
Q
Digestive Processes in the Stomach
A
- Propulsion) Peristalsis
- Mechanical Breakdown) churning of stomach during peristalsis
- Digestion
- Denaturation of protiens by HCl
- Proteins digested by pesin
- milk protein is digested by rennin in infants
- Fat) mostly digested in small intestine byt gastric and lingual lipases help.
- Absorbtion) not much abosrbed in stomach
- Secretes Intresnsic Factor for intestinal absption of B12
- prodices mature red blood cells (pernicious anemia)
- Secretes Intresnsic Factor for intestinal absption of B12
29
Q
Regulation of Gastric Secretion
A
- Gastric mucosa secretes three L of gastric juice a day
- Nural Control)
- Vagus nerve stimulation (parasympathetic) > secretion up
- Sympathetic stimulation > Secretin Down
- Hormonal control) largly Gastrin
- Stimulates secretion of acid by stomach and secretion of hormones (gastrin antagonists) by small intestine
- ACh and Histamine also stimulate pareiteal cells.
30
Q
Three Phases of Gastric Secretion
A
- Cephalic (reflex) phase) before food enters the stomach
- Triggered by aroma, sight, or though of food
- triggers vagus nerve
- Gastric Phase) when food reaches the stomach
- lasts 3-4 hours; 2/3 of gastric juice release
- Ditension) activates streach receptors for both short and long term reflxes
- Protein in stomach > rises pH of gastric content > stimulates gastrin secretion > HCl release.
- Low ph Inhibits gastrin
- Intestinal Phase) partially digested food enters the small intestine
- Stimulated by food entering the duodenim. Intestinal (enteric) gastrin release stimuates intestinal activity
- Inhibition) Dissention of the duodenum or presensce of acidic, fatty or chyme all tell stomach to stop (decrease gastric emptying)
31
Q
Enterogastric Reflex and En
A
- Inhibits acid secretion in the stomach by short and long reflexes
- Enterogastrones) hormones release by a scattering of enteroendocrine cells in duodenal mucosal epithelium.
- Secretin and Cholecystokinin (CCK)
- all inhibit gastric secretion
32
Q
Gastric Contactile Activity
A
- Peristaltic waves
- move toward pylorus at a rate of 3 per min; more vigurous near pylorus.
- each wave squirts 3 ml or less of chyme into the small intestine
- the rest (~27 or so) is propelled backward where it it mixxed more
*
33
Q
Refulation of Gastric (stomach) emptying
A
- Larger meal = faster absorption of liquid componats
- stomach needs longer to absorb solid compnants
- As Chyme enters Duodenum
- receptors repond to streatch and chemical signals
- Initiates entrogastric reflex and hormonal mechanisms to inhibit secretion and duodenal filling
- Carb Rich chyme moves quickly through duodenum
- Fat chyme remains in duodenum 6 hours or more
34
Q
Vomiting (emesis)
A
- Causesed by
- Extreme stretching of stomach or intestine
- Intestinal irritants, e.g., bacterial toxins, excessive alcohol, spicy food, certain drugs
- Excessive vomiting > dehydration, electrolyte and
acid-base imbalances (alkalosis)
35
Q
Liver
A
- Bile Production
- bile) fat emulsifier that breaks fat into tiny particles
- Largest Gland in the body
- Four lobes) left right, cudate and quadreate
- Lesser Omentum) anchors liver to lesser curvate of the stomach
- Hepatic artery/ vein enter at porta hepatis
- Bile leaves the liver through the left and right hepatic ducts
- fuse to form large common hepatic duct > cystic duct > bile duct in gall bladder
36
Q
Liver Microscopic Anatomy
A
- Liver Lobules) Structural and functional units
- Hepatocytes) liver cells. Radiate outward from a centeal vein running longitudallly to axis of the lobule
- Portal Triad) corner of each lobule
- Branch of hepatic artery) supplies O2
- Hepatic Portal Vein) brings in nutrient ruch blood
- Bile Duct) recives bile from bile canaliculi
- Liver Sinusoids) behind hepatic plates
- heavily fenestrated
- Hepatic/ Stellate macrophages) remove debris and old RBC’s
37
Q
Bile
A
- Yellow-Green, alkaline solution containing
- Bile salts) cholesterol dericatives that function in fat digestion and absorption.
- Bilirubin) cheif bile pigment. Yellow waste from the heme- part of hemoglobin
38
Q
The Gallbladder
A
• Thin-walled muscular sac on inferior surface of liver
• Stores and concentrates bile
• Muscular contractions release bile via cystic duct,
which flows into bile duct
39
Q
Pancreas
A
- Deep to Greater Curvature of the stomach. Head encircled by Duodenum; tail next to the spleen
- Produces enzymes that break down all categoreis of food
- Endocrine) secrerete insulin and glucagon (pancreatic inluts)
- Exocrine) secrete pancreatic juice (acini and ducts)
- Zymogen Granules) of acini cells contain digestive Proenzymes
- Pancreatic Juice) 1200-1500 ml per day
- Electrolytes (HCO3-)
- pH 8. Alkaline nutralizes chyme for intestinal enzymes
- Amlyase (starch) Lipase (lipids) Nucleases (nucleaic acids) Proteases (Proteins; secreted in inactive form to protect pancreas)
- Trypsinogen > activated trypsinogen > activtaes carboxipeptidase and chymotrypsin.
40
Q
Bile / Pancreatic Secretion into Small Intestine
A
- Bile Duct (liver) and Main Pancreatic Duct
- Join a in the wall of Duodenunm at Hepatopancreatic ampulla
- Opens into Duodnum at Major Duodenal Papillla
- Controled by Hepatopancratic Spinchter
- Acessory Pancratic Duct) empties directly into duodenum just proximal to midn duct. Just Pancreeas
41
Q
Regulation of Bile/ Pancreatic Secretion
A
- Hormonal and Nueral Stimuli both regulate secretion of bile/ Pancreatic juice
- CCK
- Stimulated by proteins and Fats in the Chyme
- Induces secretion of Pancreatic Juice from Acinar cells of pancreas
- Causes gall bladder constriction
- Causes Hepatopancratic Sphincter to Relax (release of bile/pancreatic enzymes)
- Secretin
- Stimulated by acidic chyme
- Causes secretion of HCO3- fom duct cells of pancreas
- Minor stimilus for Bile production
- Bile
- Bile Salts returning from enterohepatic circulation stimulate more bile secretion.
- Vagus Nerve
- Weakley stimulates pancreas and gallbladder during cephalic and gastric phases.
42
Q
Gross Anatomy of The Small Intestine
A
- Major Organ of Digestion and Absorption
- 2-4 m long (7-13ft) Half of the diameter of the large intstine
- Longest part of alamentary canal
- Duodenum
- Mostly a Retroperitonial Organ
- about 25 cm long (10 in)
- Jejunum) Extends from duodenum to ileum
- about 2.5 m (8ft) long
- Illeum) Joins large intstine at ileocecal valve.
- about 3.6 m (12ft) long.
- Fan Shaped Mesentary) supports jejunum and ileum from posterior wall.
- Innervation
- Parasympatetic) vagus
- Sympatetic) Thoracic Splanchnic Nerves
- Both relayed through superior mesentatic and celiac plexuses’
- Blood Vessels)
- Mesentaric Arteries
- Mesentatic Veins > Hepatic Portal Vein> Liver
43
Q
Modifications of The small intestine for absorption
A
- Increase surface area of proximal part for nutrient absorption
- Circular Folds)
- Permanent folds that force chume to spiral through lumen
- Slows movment which allows more time for nutrient absorption
- Vili
- Fingerlike projections of mucosa
- Each vilus has a capilary bed and Lacteal (lymphatic) capilary for absorption
- Microvilli (Brush boarder)
- Long, cytoplasmic extensions of absorptive cells of mucosa
- Contain encymes for Carb and Protein digestion (Brush Boarder Enzymes)
44
Q
Histology of Small Intestine Wall
A
- Intestinal Crypts) Tubular Glands located between the Vili in the mucosa
- decrease in number the further down the small intestine you go
- Five Major cell types
- Enterocytes)
- Villi) Primary responsibility is absortion in the villi
- Crypts) they produce intestinal juice which serves as a carrier fluid for absorbing nutritnes
- Goblet Cells) secrete mucus in villi and crypts
- Enteroednocrine Cells)
- secrete Enterogastrones (secretin, Cholecysotokinin)
- Paneth Cells
- Located deep in the crypts
- Secrete antimicrobial agents (defensins and lysozyme)
- Stem Cells
- Divide in the bottom of crypts
- daughter cells differentiate to become all other types of cells
- most cells migrate up, paneth cells migrate to the bottom of the crypts.
45
Q
Mucosa of Small Intesine
A
- Mucosa-Associated Lymphoid Tissue (MALT)
- Included induivudual lymphoid Follicles and Aggregated Lymphoid Nodules (Peyer’s Patches)
- Peyer’s Patches are more abundent in the distal part of small intestine (more bacteria)
46
Q
Intestinal Juice
A
- 1-2L Secreted Daily; Major Stimulus for production comes from hypertonic or acidic chyme
- Slightly alkaline
- Isotinic with blood plasma (7.35-7.45 pH)
47
Q
Digestion Processes in the Small Intestine
A
- Chyme from stomach contains partially diegested Carbs, Proteins and undigested Fats
- spends 3-6 hours in small intestine
- Most water and all nutrients are absorbed
- Enymes for digestion
- Most substances for digestion; bile, enzymes except brush boarder, and bicarbonate ions, are imported from the liver or pancreas
- If either organ’s function is impeded our ability to digest food goes down.
- Regulating Chyme Entry
- Chyme is hypertonic = if a bunch rushes into the duodenum and small intestine it would pull water away from the capalaries of Villi
- Low pH of chyme must be adjusted and chyme must be well mixed
- Enterogastric reflex and enterogastrones carfully controls food movement into the small intestine.
48
Q
Mobility of the Small Intestine
A
- After a meal
- Small intesine has contracting rings of smooth muscle which simply move the chyme back and forward.
- Stomach Peristalsis initates these movments
- Segmentation
- Most common motion of small intestine; Initated by intrnsic pacemaker cells
- Mixes/ Moves contents to the end
- Increased by Parasumpatetic tone
- Bewteen Meals
- True Peristalsis occurs only after most nutrients have been absorbed
- Segmenting movements wane and duodenal mucosa begins to release Motilin
49
Q
Illeocecal Valve Control
A
- Illeocecal Valve is closed most of the time
- Two mechanisms cause it to relax and let chyme to the small intesine
- Gastorieal Reflex
- Long nueral reflex triggered by stomach activity
- Increases force of segmentation in ileum and relaxes the valve
- Gastrin)
- Hormone released by stomach
- Increases mobility of ileum and relaxes the valve
- Flaps close when chyme exerts backwards pressure
50
Q
Large Intestine
A
- Ileoceal Valve to anus > Diameter is 7cm and is about 1.5 m
- Teniae Coli “ribbons of the colon”
- three bands of longicudinal smooth muslce in muscularis
- Hausta (Singular hasturm)
- Pocketlike sacs cause by tone of teniae coli
- Epilolic Appendages (membrane covered)
- Fat-filled pouches of visceral peritoneum
51
Q
Subdivisions of the Large Intestine
A
- Cecum) First Part of the larfe intestine
- Appendix) masses of lymphoid tissue; contains MALT
- storehouse of bacteria; recolonize the gut when needed
- Suseptiable to blockage
- Ascending Colon) Right side to level of kidney
- Right Colic > (hepatic) flexure
- Transsverse colon
- Hepatic Flexure > Transverse Colon > Left colic (splenic) flexure
- Descening colon
- Splenic flexure > Descending colon
- Sigmoid colon
- in the pelvis
- Rectum
- Thre folds called rectal valves (stop feces being passed with gas)
- Anal Canal
- Last segemt of large intestine, opens to body exterior
- Internal Anal Sphincter) smooth muscle
- External Anal Sphincter) skeletal muscle
- Colon is Retroperitonal
- Except for transverse and sigmoid parts. (Anchored to mesenary sheets called mesocolons)
52
Q
Large Intestine: Microscopic Anatomy
A
- Wall of Large Intsinte differs in several ways from the small intestine
- Deeper Crypts with termendous globlet cells
- Mucus eses the passage of feces
- Thicker mucose of simple columnar epithelium
- Anal Canal) stratified squamous to withstand abrasion
- No absorbtion.
- Folds are called anal colums
- Anal sinuses) are recesses between anal columns
53
Q
Bacterial Flora
A
- Consists of over a thousand types of bacteria
- couple pounds of body weight
- Most colanize colan via the anus
- Some enter from small intestine
- Metabolic Functions
- recover energy from otherwise indgestible foods and syntethizize some vitamens
- Fermentation
- bacetria ferment indigestible carbohydrates. Can be absored by body cells afetwards
- Produces gases (more when we eat indigesable carbs)
- Vitamin Syntesis
- B complex vitamins and some vitamin K are produced by gut bacteria
54
Q
Digestive Processes In the Large Intestine
A
- Residue remains in large intesine 12-24 hours
- No food breakdown except for gut bacteria
- Vitamns, water, and electrolytes reclaimes
55
Q
Mobility of the Large intestine
A
- Haustral Contactions
- Slow segmenting movments that last about one min
- Occur every 30 min or so
- Contrat in respone to distension
- Mass Movments
- Presence of food in stomach activates gastroieal reflex in the small intesinte and gastrocholic rflex in colon
- Activates three to four slow powerful peristaltic waves.
- Fiber in diet makes colon movments easier
56
Q
Homeostatic Imbalance of the Colon
A
- Diverticula (herniations of colon mucose dure to a low fiber diet.
- Narrowed colon > stonger contractions > more pressure > hernia
- Affects sigmoid colon
- IBS) Reoccuring abdominal pain, stool changes, bloating, flatuence, nause and depression
57
Q
Defication
A
- Mass Movments force feces toward Rectum
- initited spinal Defication Reflex
- Contraction of sigmoid colon and rectum
- Relax internal anal sphincter
- Assisted by vasalva’s manuever
