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SISTEMA DIGESTIVO
SISTEMA DIGESTIVO: bioreactores
SISTEMA DIGESTIVO
Es un tubo abierto: extensión del
medio ambiente!
S
E
absorción
Digestión:
•mecánica (trituración)
•química (enzimas hidrolíticas)
Sistema de Tubos y Esfínteres
-
Direccionalidad
-
Compartimentalización
-
Almacenamiento.
EL TRACTO DIGESTIVO
Anatomía del sistema digestivo
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Digestive tract
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Accessory organs
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Alimentary tract or
canal
GI tract
Primarily glands
Regions
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Mouth or oral cavity
Pharynx
Esophagus
Stomach
Small intestine
Large intestine
Anus
Cavidad oral
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Mouth or oral cavity
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Lips (labia) and
cheeks
Palate: Oral cavity
roof
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Vestibule: Space
between lips or cheeks
and alveolar processes
Oral cavity proper
Hard and soft
Palatine tonsils
Tongue: Involved in
speech, taste,
mastication,
swallowing
Dientes
Dientes
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Two sets
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Primary, deciduous,
milk: Childhood
Permanent or
secondary: Adult (32)
Types
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Incisors, canine,
premolar and molars
Glándulas salivales
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Produce saliva
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Prevents bacterial
infection
Lubrication
Contains salivary
amylase
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Breaks down starch
Three pairs
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Parotid: Largest
Submandibular
Sublingual: Smallest
Producción de saliva
- 99.5 % agua
- HCO3- , ph 6.5
- moco, enzimas
SECRECIONES SALIVALES
1. Secreción serosa: amilasa salival:
hidrólisis a-1-4 polisacáridos
2. Secreción mucosa:
lubrica y protege.
3. IgA y lisozima:
antimicrobiana
Reflejo de deglución
Fase voluntaria
Fase refleja
Fase refleja
Bolo alimenticio desde boca a
faringe
Apertura del esófago,
cierre de laringe
Transporte por esófago
Peritoneo y Mesenterios
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Peritoneum
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Visceral: Covers organs
Parietal: Covers interior
surface of body wall
Retroperitoneal: Behind
peritoneum as kidneys,
pancreas, duodenum
Mesenteries
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Routes which vessels and
nerves pass from body wall to
organs
Greater omentum
Lesser omentum
Histología del tracto digestivo
Estómago
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Openings
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Gastroesophageal:
To esophagus
Pyloric: To
duodenum
Regions
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Cardiac
Fundus
Body
Pyloric
Histología del estómago
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Layers
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Serosa or visceral
peritoneum:
Outermost
Muscularis: Three
layers
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Outer longitudinal
Middle circular
Inner oblique
Submucosa
Mucosa
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Gastric pits and glands:
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Contain cells
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Surface mucous: Mucus
Mucous neck: Mucus
Parietal: Hydrochloric acid
and intrinsic factor
Chief: Pepsinogen
Endocrine: Regulatory
hormones
Secreción de HCl
en células parietales
Barrera mucus –
HCO3
Pepsinógeno: proenzima
Fases de la secreción
gástrica
FASE CEFÁLICA
- percepción sensorial del alimento
FASE GÁSTRICA
- presencia del alimento
Ondas de mezcla
FASE INTESTINAL
VIP
Gastrin
Duodeno y Pancreas
Pancreas
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Anatomy
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Endocrine
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Exocrine
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Pancreatic islets produce
insulin and glucagon
Acini produce digestive
enzymes and HCO3-
Regions: Head, body, tail
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Secretions
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Pancreatic juice (exocrine)
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Trypsin
Chymotrypsin
Carboxypeptidase
Pancreatic amylase
Pancreatic lipases
Elastase
Nucleases (DNA, RNA)
HCO3-, H20
Secreción de HCO3-
Enzimas
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Trypsinogen
Chymotrysinogen
Carboxypeptidases
Pro-elastase
Phospholipase
pancreatic lipase
Pancreatic amylase
Hígado
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Lobes
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Major: Left and right
Minor: Caudate and
quadrate
Ducts
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Common hepatic
Cystic
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From gallbladder
Common bile
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Joins pancreatic duct at
hepatopancreatic ampulla
Conductos
Histología del hígado
triada
portal
Figure 24.20a, b
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Bile production
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Hepatocytes remove ammonia and convert to urea
Cholesterol and tryglicerid synthesis
Gluconeogénesis, glucogénesis, glucogenólisis
Phagocytosis
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Glycogen, fat, vitamins, copper and iron
Aminoacid synthesis and degradation
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Salts emulsify fats, contain pigments as bilirubin
Storage
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Funciones del hígado
Kupffer cells phagocytize worn-out and dying red and white blood cells,
some bacteria
Plasma proteins and hemostatic factors
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Albumins, globulins, fibrinogen, heparin, K vitamin
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Detoxification and drug metabolism
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Hormonal secretion: trombopoietin, angotensinogen
Bilis
…each day around 600 ml of bile is produced…
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Bile cholic acid – Na+
Phospholipids
Cholesterol
Waste products (Bilirubin
and biliverdin, chol., drugs)
Electrolytes
Mucin
HCO3-
Intestino delgado
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Site of greatest amount of
digestion and absorption
Divisions
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Modifications
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Duodenum
Jejunum
Ileum: Peyer’s patches or
lymph nodules
Circular folds or plicae
circulares, villi, lacteal,
microvilli
Cells of mucosa
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Absorptive, goblet, granular,
endocrine
Secreciones del int. delgado
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Mucus and HCO3
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Enzymes
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Protects against digestive enzymes and stomach acids
Disaccharidases
Peptidases
Nucleotidases, nucleosidases
Enteroquinase: tripsinógeno  tripsina
Duodenal glands (Brünner)
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Stimulated by vagus nerve, secretin, chemical or tactile
irritation of duodenal mucosa
Duodeno
llegan: quimo ácido, jugos pancreáticos, bilis
Absorción intestinal
Monosacáridos
Lípidos
Lipoproteinas
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Types
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Chylomicrons
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VLDL
LDL
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Enter lymph
Transports cholesterol
to cells
HDL
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Transports cholesterol
from cells to liver
Intestino grueso
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Extends from ileocecal junction to anus
Consists of cecum, colon, rectum, anal canal
Movements sluggish (18-24 hours)
Intestino grueso: Absorción de H2O y
Defecación
Figure 21-27: Anatomy of the large intestine
Large Intestine
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Cecum
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Colon
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Ascending, transverse, descending, sigmoid
Rectum
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Blind sac, vermiform appendix attached
Straight muscular tube
Anal canal
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Internal anal sphincter (smooth muscle)
External anal sphincter (skeletal muscle)
Histology of Large Intestine
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Water and electrolyte
secretion &/or
absorption
Bacterial fermentation
of HC
Bacterial synthesis of
Vit. K , B.
Bacterial degradation of
bile acids and esterols
Absortion of lactate &
butyrate
Prevents infections and
immune alterations
Figure 21-28: NaCl reabsorption by colonocytes
Figure 21-29: NaCl secretion by colonic crypt cells
Toxina colérica
- ADP-ribosilación de Ga
-  G-GTP  AC  cAMP  PKA  p-CFTR
PKA
Secreciones
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Mucus provides protection
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Parasympathetic stimulation increases rate of goblet
cell secretion
Pumps
Exchange of bicarbonate ions for chloride ions
 Exchange of sodium ions for hydrogen ions
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Bacterial actions produce gases called flatus
Reflejos en
Colon y Recto
Secreciones del tubo digestivo
Enzimas del tubo digestivo
Regulación nerviosa y
hormonal
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Nervous regulation
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Involves enteric nervous
system
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Types of neurons: sensory,
motor, interneurons
Coordinates peristalsis
and regulates local
reflexes
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Chemical regulation
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Production of hormones
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Gastrin, secretin
Production of paracrine
chemicals
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Histamine
Help local reflexes in ENS
control digestive
environments as pH levels
Hormonas gastrointestinales
Water and Ions:
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Water
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Can move in either direction
across wall of small intestine
depending on osmotic
gradients
Ions
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Sodium, potassium, calcium,
magnesium, phosphate are
actively transported
Effects of Aging
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Decrease in mucus layer, connective tissue,
muscles and secretions
Increased susceptibility to infections and toxic
agents

Ulcerations and cancers
Chemical Events in Digestion: Carbohydrates
1. Shows carbohydrate
digestion.
2. Note the small
intestine’s role in
conversion to monoand di-saccharides.
Chemical Events in Digestion: Lipids
3. Lipid digestion is
shown here.
4. Note the conversion
to monoglycerides in
the small intestine
due to bile salts and
pancreatic lipase.
Chemical Events in Digestion: Proteins
5. Digestion of proteins.
6. Note stomach’s
conversion to
polypeptides.
7. Small intestine
converts to short
peptides and amino
acids for intestinal
absorption.
Gastric Secretion
1. Thin, strongly acidic (pH: 1 to 3), almost
colorless liquid. It is secreted by the
glands in the lining of the stomach.
2. Essential constituents are the digestive
enzymes pepsin and renin, hydrochloric
acid, and mucus.
3. Certain cells of the stomach lining secrete
intrinsic factor which is necessary for the
absorption of vitamin B12.
Secretion rates of Gastric juice
Path followed by bile juice in liver
and gall bladder
Pancreatic Secretion
Production of Pancreatic Secretion
Pancreatic Secretion
1. Clear, alkaline secretion of the pancreas
containing enzymes that aid in the
digestion of proteins, carbohydrates, and
fats.
2. There are mainly two types of
pancreatic secretions:
- Bicarbonate Secretion,
- Enzyme Secretion.
Secretion of Pancreatic juice
Chemistry of Digestion: Fats
Figure 21-8: Fat digestion
Gastric hormones:
Cephalic and Oral Phases of
Digestion
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Cephalic: anticipation of food
CNS  ANS long reflex
 Enteric  cells short reflex
 GI motility
 GI secretions
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Mouth: starts digestion
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Grind, mix & liquefy
Saliva: water, enzymes, mucus & lysozyme
Phases of Digestion: Overview
Figure 21-11: Overview of functions in different regions of the digestive system
Regulating Digestion: CNS and
Enteric Nervous System (ENS)
Figure 21-9: The enteric nervous system
Cephalic and Oral Phases of
Digestion
Figure 21-12: Long and short reflexes in the stomach
Movement in small intestine:
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Mixing: Segmental contraction that occurs in small intestine
Secretion: Lubricate, liquefy, digest
Digestion: Mechanical and chemical
Absorption: Movement from tract into circulation or lymph
Elimination: Waste products removed from body