Pharynx From the mouth, the oro- and laryngopharynx allow passage of: From the mouth, the oro- and...
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Transcript of Pharynx From the mouth, the oro- and laryngopharynx allow passage of: From the mouth, the oro- and...
PharynxPharynx
From the mouth, the oro- and laryngopharynx From the mouth, the oro- and laryngopharynx allow passage of:allow passage of: Food and fluids to the esophagusFood and fluids to the esophagus Air to the tracheaAir to the trachea
Lined with stratified squamous epithelium and Lined with stratified squamous epithelium and mucus glandsmucus glands
Has two skeletal muscle layersHas two skeletal muscle layers Inner longitudinal Inner longitudinal Outer pharyngeal constrictors Outer pharyngeal constrictors
EsophagusEsophagus
Muscular tube going from the laryngopharynx Muscular tube going from the laryngopharynx to the stomachto the stomach
Travels through the mediastinum and pierces Travels through the mediastinum and pierces the diaphragm the diaphragm
Joins the stomach at the cardiac orifice Joins the stomach at the cardiac orifice
Esophageal CharacteristicsEsophageal Characteristics
Esophageal mucosa – nonkeratinized stratified Esophageal mucosa – nonkeratinized stratified squamous epithelium squamous epithelium
The empty esophagus is folded longitudinally The empty esophagus is folded longitudinally and flattens when food is presentand flattens when food is present
Glands secrete mucus as a bolus (compacted Glands secrete mucus as a bolus (compacted food product) moves through the esophagusfood product) moves through the esophagus
Muscularis changes from skeletal (superiorly) Muscularis changes from skeletal (superiorly) to smooth muscle (inferiorly)to smooth muscle (inferiorly)
Digestive Processes in the MouthDigestive Processes in the Mouth
Food is ingestedFood is ingested Mechanical digestion begins (chewing)Mechanical digestion begins (chewing) Propulsion is initiated by swallowingPropulsion is initiated by swallowing Salivary amylase begins chemical breakdown Salivary amylase begins chemical breakdown
of starchof starch The pharynx and esophagus serve as conduits The pharynx and esophagus serve as conduits
to pass food from the mouth to the stomachto pass food from the mouth to the stomach
Deglutition (Swallowing)Deglutition (Swallowing)
Coordinated activity of the tongue, soft palate, Coordinated activity of the tongue, soft palate, pharynx, esophagus, and 22 separate muscle pharynx, esophagus, and 22 separate muscle groupsgroups
Buccal phase – bolus is forced into the Buccal phase – bolus is forced into the oropharynx oropharynx
Deglutition (Swallowing)Deglutition (Swallowing)
Pharyngeal-esophageal phase – controlled by the Pharyngeal-esophageal phase – controlled by the medulla and lower ponsmedulla and lower pons All routes except into the digestive tract are sealed All routes except into the digestive tract are sealed
offoff Peristalsis moves food through the pharynx to Peristalsis moves food through the pharynx to
the esophagusthe esophagus
StomachStomach Chemical breakdown of proteins begins and Chemical breakdown of proteins begins and
food is converted to chymefood is converted to chyme Cardiac region – surrounds the cardiac orificeCardiac region – surrounds the cardiac orifice Fundus – dome-shaped region beneath the Fundus – dome-shaped region beneath the
diaphragmdiaphragm Body – midportion of the stomachBody – midportion of the stomach Pyloric region – made up of the antrum and Pyloric region – made up of the antrum and
canal which terminates at the pyloruscanal which terminates at the pylorus The pylorus is continuous with the duodenum The pylorus is continuous with the duodenum
through the pyloric sphincterthrough the pyloric sphincter
StomachStomach
Greater curvature – entire extent of the convex Greater curvature – entire extent of the convex lateral surfacelateral surface
Lesser curvature – concave medial surfaceLesser curvature – concave medial surface Lesser omentum – runs from the liver to the Lesser omentum – runs from the liver to the
lesser curvaturelesser curvature Greater omentum – drapes inferiorly from the Greater omentum – drapes inferiorly from the
greater curvature to the small intestinegreater curvature to the small intestine
StomachStomach
Nerve supply – sympathetic and Nerve supply – sympathetic and parasympathetic fibers of the autonomic parasympathetic fibers of the autonomic nervous systemnervous system
Blood supply – celiac trunk, and Blood supply – celiac trunk, and corresponding veins (part of the hepatic portal corresponding veins (part of the hepatic portal system)system)
Microscopic Anatomy of the Microscopic Anatomy of the StomachStomach
Muscularis – has an additional oblique layer Muscularis – has an additional oblique layer that: that: Allows the stomach to churn, mix, and pummel Allows the stomach to churn, mix, and pummel
food physically food physically Breaks down food into smaller fragmentsBreaks down food into smaller fragments
Microscopic Anatomy of the Microscopic Anatomy of the StomachStomach
Epithelial lining is composed of:Epithelial lining is composed of: Goblet cells that produce a coat of alkaline mucusGoblet cells that produce a coat of alkaline mucus
The mucous surface layer traps a bicarbonate-rich fluid The mucous surface layer traps a bicarbonate-rich fluid beneath itbeneath it
Gastric pits contain gastric glands that secrete Gastric pits contain gastric glands that secrete gastric juice, mucus, and gastringastric juice, mucus, and gastrin
Glands of the Stomach Fundus Glands of the Stomach Fundus and Bodyand Body
Gastric glands of the fundus and body have a Gastric glands of the fundus and body have a variety of secretory cellsvariety of secretory cells Mucous neck cells – secrete acid mucusMucous neck cells – secrete acid mucus Parietal cells – secrete HCl and intrinsic factor Parietal cells – secrete HCl and intrinsic factor
Glands of the Stomach Fundus Glands of the Stomach Fundus and Bodyand Body
Chief cells – produce pepsinogen Chief cells – produce pepsinogen Pepsinogen is activated to pepsin by:Pepsinogen is activated to pepsin by:
HCl in the stomachHCl in the stomach Pepsin itself via a positive feedback mechanismPepsin itself via a positive feedback mechanism
Enteroendocrine cells – secrete gastrin, histamine, Enteroendocrine cells – secrete gastrin, histamine, endorphins, serotonin, cholecystokinin (CCK), and endorphins, serotonin, cholecystokinin (CCK), and somatostatin into the lamina propriasomatostatin into the lamina propria
Stomach LiningStomach Lining
The stomach is exposed to the harshest The stomach is exposed to the harshest conditions in the digestive tractconditions in the digestive tract
To keep from digesting itself, the stomach has To keep from digesting itself, the stomach has a mucosal barrier with:a mucosal barrier with: A thick coat of bicarbonate-rich mucus on the A thick coat of bicarbonate-rich mucus on the
stomach wallstomach wall Epithelial cells that are joined by tight junctionsEpithelial cells that are joined by tight junctions Gastric glands that have cells impermeable to HClGastric glands that have cells impermeable to HCl
Damaged epithelial cells are quickly replacedDamaged epithelial cells are quickly replaced
Digestion in the StomachDigestion in the Stomach
The stomach:The stomach: Holds ingested foodHolds ingested food Degrades this food both physically and chemicallyDegrades this food both physically and chemically Delivers chyme to the small intestineDelivers chyme to the small intestine Enzymatically digests proteins with pepsinEnzymatically digests proteins with pepsin Secretes intrinsic factor required for absorption of Secretes intrinsic factor required for absorption of
vitamin Bvitamin B1212
Regulation of Gastric SecretionRegulation of Gastric Secretion
Neural and hormonal mechanisms regulate the Neural and hormonal mechanisms regulate the release of gastric juicerelease of gastric juice
Stimulatory and inhibitory events occur in Stimulatory and inhibitory events occur in three phasesthree phases Cephalic (reflex) phase: prior to food entryCephalic (reflex) phase: prior to food entry Gastric phase: once food enters the stomachGastric phase: once food enters the stomach Intestinal phase: as partially digested food enters Intestinal phase: as partially digested food enters
the duodenum the duodenum
Cephalic PhaseCephalic Phase
Excitatory events include:Excitatory events include: Sight or thought of foodSight or thought of food Stimulation of taste or smell receptorsStimulation of taste or smell receptors
Inhibitory events include:Inhibitory events include: Loss of appetite or depressionLoss of appetite or depression Decrease in stimulation of the parasympathetic Decrease in stimulation of the parasympathetic
divisiondivision
Gastric PhaseGastric Phase
Excitatory events include:Excitatory events include: Stomach distension Stomach distension Activation of stretch receptors (neural activation)Activation of stretch receptors (neural activation) Activation of chemoreceptors by peptides, Activation of chemoreceptors by peptides,
caffeine, and rising pH caffeine, and rising pH Release of gastrin to the bloodRelease of gastrin to the blood
Gastric PhaseGastric Phase
Inhibitory events include:Inhibitory events include: A pH lower than 2 A pH lower than 2 Emotional upset that overrides the parasympathetic Emotional upset that overrides the parasympathetic
divisiondivision
Intestinal PhaseIntestinal Phase Excitatory phase – low pH; partially digested Excitatory phase – low pH; partially digested
food enters the duodenum and encourages food enters the duodenum and encourages gastric gland activitygastric gland activity
Inhibitory phase – distension of duodenum, Inhibitory phase – distension of duodenum, presence of fatty, acidic, or hypertonic chyme, presence of fatty, acidic, or hypertonic chyme, and/or irritants in the duodenumand/or irritants in the duodenum Initiates inhibition of local reflexes and vagal Initiates inhibition of local reflexes and vagal
nucleinuclei Closes the pyloric sphincterCloses the pyloric sphincter Releases enterogastrones that inhibit gastric Releases enterogastrones that inhibit gastric
secretionsecretion
Regulation and Mechanism of Regulation and Mechanism of HCl SecretionHCl Secretion
HCl secretion is stimulated by ACh, histamine, HCl secretion is stimulated by ACh, histamine, and gastrin through second-messenger systemsand gastrin through second-messenger systems
Antihistamines block HAntihistamines block H22 receptors and receptors and
decrease HCl releasedecrease HCl release
Response of the Stomach to Response of the Stomach to FillingFilling
Stomach pressure remains constant until about Stomach pressure remains constant until about 1L of food is ingested1L of food is ingested
Relative unchanging pressure results from Relative unchanging pressure results from reflex-mediated relaxation and plasticityreflex-mediated relaxation and plasticity
Response of the Stomach to Response of the Stomach to FillingFilling
Reflex-mediated events include:Reflex-mediated events include: Receptive relaxation – as food travels in the Receptive relaxation – as food travels in the
esophagus, stomach muscles relaxesophagus, stomach muscles relax Adaptive relaxation – the stomach dilates in Adaptive relaxation – the stomach dilates in
response to gastric fillingresponse to gastric filling Plasticity – intrinsic ability of smooth muscle Plasticity – intrinsic ability of smooth muscle
to exhibit the stress-relaxation responseto exhibit the stress-relaxation response
Gastric Contractile ActivityGastric Contractile Activity
Peristaltic waves move toward the pylorus at Peristaltic waves move toward the pylorus at the rate of 3 per minutethe rate of 3 per minute
This basic electrical rhythm (BER) is initiated This basic electrical rhythm (BER) is initiated by pacemaker cells (cells of Cajal)by pacemaker cells (cells of Cajal)
Gastric Contractile ActivityGastric Contractile Activity
Most vigorous peristalsis and mixing occurs Most vigorous peristalsis and mixing occurs near the pylorusnear the pylorus
Chyme is either:Chyme is either: Delivered in small amounts to the duodenum orDelivered in small amounts to the duodenum or Forced backward into the stomach for further Forced backward into the stomach for further
mixingmixing
Regulation of Gastric EmptyingRegulation of Gastric Emptying
Gastric emptying is regulated by:Gastric emptying is regulated by: The neural enterogastric reflexThe neural enterogastric reflex Hormonal (enterogastrone) mechanismsHormonal (enterogastrone) mechanisms
These mechanisms inhibit gastric secretion These mechanisms inhibit gastric secretion and duodenal fillingand duodenal filling
Regulation of Gastric EmptyingRegulation of Gastric Emptying
Carbohydrate-rich chyme quickly moves Carbohydrate-rich chyme quickly moves through the duodenum through the duodenum
Fat-laden chyme is digested more slowly Fat-laden chyme is digested more slowly causing food to remain in the stomach longercausing food to remain in the stomach longer
Small Intestine: Gross AnatomySmall Intestine: Gross Anatomy
Runs from pyloric sphincter to the ileocecal Runs from pyloric sphincter to the ileocecal valve valve
Has three subdivisions: duodenum, jejunum, Has three subdivisions: duodenum, jejunum, and ileumand ileum
Small Intestine: Gross AnatomySmall Intestine: Gross Anatomy
The bile duct and main pancreatic duct:The bile duct and main pancreatic duct: Join the duodenum at the hepatopancreatic ampulla Join the duodenum at the hepatopancreatic ampulla Are controlled by the sphincter of OddiAre controlled by the sphincter of Oddi
The jejunum extends from the duodenum to The jejunum extends from the duodenum to the ileumthe ileum
The ileum joins the large intestine at the The ileum joins the large intestine at the ileocecal valveileocecal valve
Small Intestine: Microscopic Small Intestine: Microscopic AnatomyAnatomy
Structural modifications of the small intestine Structural modifications of the small intestine wall increase surface areawall increase surface area Plicae circulares: deep circular folds of the mucosa Plicae circulares: deep circular folds of the mucosa
and submucosaand submucosa Villi – fingerlike extensions of the mucosaVilli – fingerlike extensions of the mucosa Microvilli – tiny projections of absorptive mucosal Microvilli – tiny projections of absorptive mucosal
cells’ plasma membranescells’ plasma membranes
Small Intestine: Histology of the Small Intestine: Histology of the WallWall
The epithelium of the mucosa is made up of:The epithelium of the mucosa is made up of: Absorptive cells and goblet cells Absorptive cells and goblet cells Enteroendocrine cells Enteroendocrine cells Interspersed T cells called intraepithelial Interspersed T cells called intraepithelial
lymphocytes (IELs)lymphocytes (IELs) IELs release cytokinesIELs release cytokines
Small Intestine: Histology of the Small Intestine: Histology of the WallWall
Cells of intestinal crypts secrete intestinal juiceCells of intestinal crypts secrete intestinal juice Peyer’s patches are found in the submucosa Peyer’s patches are found in the submucosa Brunner’s glands in the duodenum secrete Brunner’s glands in the duodenum secrete
alkaline mucus alkaline mucus
Intestinal JuiceIntestinal Juice
Secreted by intestinal glands in response to Secreted by intestinal glands in response to distension or irritation of the mucosadistension or irritation of the mucosa
Slightly alkaline and isotonic with blood Slightly alkaline and isotonic with blood plasmaplasma
Largely water, enzyme-poor, but contains Largely water, enzyme-poor, but contains mucusmucus
LiverLiver
The largest gland in the bodyThe largest gland in the body Superficially has four lobes – right, left, Superficially has four lobes – right, left,
caudate, and quadratecaudate, and quadrate The falciform ligament:The falciform ligament:
Separates the right and left lobes anteriorlySeparates the right and left lobes anteriorly Suspends the liver from the diaphragm and Suspends the liver from the diaphragm and
anterior abdominal wallanterior abdominal wall
LiverLiver
The ligamentum teres:The ligamentum teres: Is a remnant of the fetal umbilical veinIs a remnant of the fetal umbilical vein Runs along the free edge of the falciform ligamentRuns along the free edge of the falciform ligament
Liver: Associated StructuresLiver: Associated Structures
The lesser omentum anchors the liver to the The lesser omentum anchors the liver to the stomachstomach
The hepatic blood vessels enter the liver at the The hepatic blood vessels enter the liver at the porta hepatisporta hepatis
The gallbladder rests in a recess on the inferior The gallbladder rests in a recess on the inferior surface of the right lobesurface of the right lobe
Liver: Associated StructuresLiver: Associated Structures
Bile leaves the liver via:Bile leaves the liver via: Bile ducts, which fuse into the common hepatic Bile ducts, which fuse into the common hepatic
duct duct The common hepatic duct, which fuses with the The common hepatic duct, which fuses with the
cystic ductcystic duct These two ducts form the bile ductThese two ducts form the bile duct
Figure 23.24c
Liver: Microscopic AnatomyLiver: Microscopic Anatomy
Hexagonal-shaped liver lobules are the Hexagonal-shaped liver lobules are the structural and functional units of the liverstructural and functional units of the liver Composed of hepatocyte (liver cell) plates Composed of hepatocyte (liver cell) plates
radiating outward from a central veinradiating outward from a central vein Portal triads are found at each of the six corners of Portal triads are found at each of the six corners of
each liver lobuleeach liver lobule
Figure 23.24d
Liver: Microscopic AnatomyLiver: Microscopic Anatomy
Portal triads consist of a bile duct andPortal triads consist of a bile duct and Hepatic artery – supplies oxygen-rich blood to the Hepatic artery – supplies oxygen-rich blood to the
liverliver Hepatic portal vein – carries venous blood with Hepatic portal vein – carries venous blood with
nutrients from digestive visceranutrients from digestive viscera
Liver: Microscopic AnatomyLiver: Microscopic Anatomy
Liver sinusoids – enlarged, leaky capillaries Liver sinusoids – enlarged, leaky capillaries located between hepatic plateslocated between hepatic plates
Kupffer cells – hepatic macrophages found in Kupffer cells – hepatic macrophages found in liver sinusoidsliver sinusoids
Liver: Microscopic AnatomyLiver: Microscopic Anatomy
Hepatocytes’ functions include:Hepatocytes’ functions include: Production of bileProduction of bile Processing bloodborne nutrientsProcessing bloodborne nutrients Storage of fat-soluble vitaminsStorage of fat-soluble vitamins DetoxificationDetoxification
Secreted bile flows between hepatocytes Secreted bile flows between hepatocytes toward the bile ducts in the portal triads toward the bile ducts in the portal triads
Composition of BileComposition of Bile A yellow-green, alkaline solution containing A yellow-green, alkaline solution containing
bile salts, bile pigments, cholesterol, neutral bile salts, bile pigments, cholesterol, neutral fats, phospholipids, and electrolytesfats, phospholipids, and electrolytes
Bile salts are cholesterol derivatives that:Bile salts are cholesterol derivatives that: Emulsify fatEmulsify fat Facilitate fat and cholesterol absorptionFacilitate fat and cholesterol absorption Help solubilize cholesterolHelp solubilize cholesterol
Enterohepatic circulation recycles bile salts Enterohepatic circulation recycles bile salts The chief bile pigment is bilirubin, a waste The chief bile pigment is bilirubin, a waste
product of hemeproduct of heme
The GallbladderThe Gallbladder
Thin-walled, green muscular sac on the ventral Thin-walled, green muscular sac on the ventral surface of the liversurface of the liver
Stores and concentrates bile by absorbing its Stores and concentrates bile by absorbing its water and ionswater and ions
Releases bile via the cystic duct, which flows Releases bile via the cystic duct, which flows into the bile ductinto the bile duct
Regulation of Bile ReleaseRegulation of Bile Release
Acidic, fatty chyme causes the duodenum to Acidic, fatty chyme causes the duodenum to release:release: Cholecystokinin (CCK) and secretin into the Cholecystokinin (CCK) and secretin into the
bloodstreambloodstream Bile salts and secretin transported in blood Bile salts and secretin transported in blood
stimulate the liver to produce bilestimulate the liver to produce bile Vagal stimulation causes weak contractions of Vagal stimulation causes weak contractions of
the gallbladderthe gallbladder
Regulation of Bile ReleaseRegulation of Bile Release
Cholecystokinin causes:Cholecystokinin causes: The gallbladder to contractThe gallbladder to contract The hepatopancreatic sphincter to relaxThe hepatopancreatic sphincter to relax
As a result, bile enters the duodenumAs a result, bile enters the duodenum