anatomia sist dig

7/28/2019 Anatomia Sist Dig

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Digestive System Anatomy

Digestive tract Alimentary tract or

canal

GI tract

Accessory organs Primarily glands

Regions Mouth or oral cavity

Pharynx

Esophagus Stomach

Small intestine

Large intestine

Anus


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Digestive System Regulation

Nervous regulation

Involves enteric nervous

system

Types of neurons: sensory,motor, interneurons

Coordinates peristalsis

and regulates local

reflexes

Chemical regulation

Production of hormones

Gastrin, secretin Production of paracrine

chemicals

Histamine

Help local reflexes in ENS

control digestive

environments as pH levels


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Oral Cavity

Mouth or oral cavity Vestibule: Space

between lips or cheeksand alveolar processes

Oral cavity proper

Lips (labia) and

cheeks

Palate: Oral cavityroof Hard and soft

Palatine tonsils Tongue: Involved in

speech, taste,mastication,swallowing


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Teeth

Two sets

Primary, deciduous,

milk: Childhood

Permanent orsecondary: Adult (32)

Types

Incisors, canine,

premolar and molars


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Tooth structure:


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Salivary Glands

Produce saliva Prevents bacterial

infection

Lubrication

Contains salivaryamylase

Breaks down starch

Three pairs

Parotid: Largest

Submandibular

Sublingual: Smallest


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Pharynx and Esophagus

Pharynx

Nasopharynx

Oropharynx: Transmitsfood normally

Laryngopharynx:

Transmits food

normally

Esophagus Transports food from

pharynx to stomach

Passes through esophageal

hiatus (opening) ofdiaphragm and ends atstomach Hiatal hernia

Sphincters

Upper Lower


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Deglutition (Swallowing)

Three phasesVoluntary

Bolus of food moved by tongue from oral cavity topharynx

Pharyngeal

Reflex: Upper esophageal sphincter relaxes, elevatedpharynx opens the esophagus, food pushed intoesophagus

Esophageal Reflex: Epiglottis is tipped posteriorly, larynx elevated

to prevent food from passing into larynx


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Phases of Deglutition

(Swallowing)


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Stomach Anatomy:

Openings

Gastroesophageal:

To esophagus

Pyloric: To

duodenum

Regions

Cardia

Fundus

Body

Pylor


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Stomach Histology:

Layers Serosa or visceral

peritoneum:

Outermost

Muscularis: Threelayers

Outer longitudinal

Middle circular

Inner oblique

Submucosa

Mucosa


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Phases of Gastric

Secretion


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Movements in Stomach


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Small Intestine

Site of greatest amount ofdigestion and absorption

Divisions Duodenum

Jejunum

Ileum: Peyers patches orlymph nodules

Modifications Circular folds or plicae

circulares, villi, lacteal,

microvilli Cells of mucosa

Absorptive, goblet, granular,endocrine


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Small Intestine Secretions

Mucus Protects against digestive enzymes and stomach acids

Digestive enzymes

Disaccharidases: Break down disaccharides tomonosaccharides

Peptidases: Hydrolyze peptide bonds

Nucleases: Break down nucleic acids

Duodenal glands Stimulated by vagus nerve, secretin, chemical or tactile

irritation of duodenal mucosa


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Duodenum and Pancreas


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Liver

Lobes Major: Left and right

Minor: Caudate and

quadrate

Ducts Common hepatic

Cystic

From gallbladder

Common bile

Joins pancreatic duct at

hepatopancreatic ampulla


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Functions of the Liver

Bile production Salts emulsify fats, contain pigments as bilirubin

Storage Glycogen, fat, vitamins, copper and iron

Nutrient interconversion

Detoxification Hepatocytes remove ammonia and convert to urea

Phagocytosis Kupffer cells phagocytize worn-out and dying red and white blood cells,

some bacteria

Synthesis Albumins, fibrinogen, globulins, heparin, clotting factors


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Duct System


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Gallbladder

Bile is stored and concentrated

Stimulated by cholecystokinin and vegal

stimulation

Dumps into small intestine

Production of gallstones possible

Drastic dieting with rapid weight loss


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Pancreas

Anatomy

Endocrine

Pancreatic islets produce

insulin and glucagon

Exocrine

Acini produce digestive

enzymes

Regions: Head, body, tail

Secretions

Pancreatic juice (exocrine) Trypsin

Chymotrypsin

Carboxypeptidase Pancreatic amylase

Pancreatic lipases

Enzymes that reduce DNAand ribonucleic acid

L I i


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Large Intestine:

Extends from ileocecal junction to anus

Consists of cecum, colon, rectum, anal canal

Movements sluggish (18-24 hours)


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Large Intestine

Cecum Blind sac, vermiform appendix attached

Colon Ascending, transverse, descending, sigmoid

Rectum Straight muscular tube

Anal canal Internal anal sphincter (smooth muscle) External anal sphincter (skeletal muscle)

Hemorrhoids: Vein enlargement or inflammation


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Movement in Large Intestine

Mass movements Common after meals

Local reflexes in enteric plexus Gastrocolic: Initiated by stomach

Duodenocolic: Initiated by duodenum

Defecation reflex Distension of the rectal wall by feces

Defecation Usually accompanied by voluntary movements to expel feces

through abdominal cavity pressure caused by inspiration


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Digestion Absorption


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Digestion, Absorption,

Transport

Digestion

Breakdown of food molecules for absorption into

circulation

Mechanical: Breaks large food particles to small

Chemical: Breaking of covalent bonds by digestive

enzymes

Absorption and transport Molecules are moved out of digestive tract and into

circulation for distribution throughout body


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Functions of the Liver

Bile production Salts emulsify fats, contain pigments as bilirubin

Storage Glycogen, fat, vitamins, copper and iron

Nutrient interconversion

Detoxification Hepatocytes remove ammonia and convert to urea

Phagocytosis Kupffer cells phagocytize worn-out and dying red and white blood cells,

some bacteria

Synthesis Albumins, fibrinogen, globulins, heparin, clotting factors


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Lipoproteins

Types

Chylomicrons

Enter lymph

VLDL LDL

Transports cholesterol

to cells

HDL Transports cholesterol

from cells to liver


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W d I


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Water and Ions:

Water Can move in either direction

across wall of small intestine

depending on osmotic

gradients

Ions

Sodium, potassium, calcium,

magnesium, phosphate are

actively transported


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