The Department of Human anatomyThe Department of Human anatomy

Splanchnology.

Digestive systemPart – 1

Splanchnology-branch of anatomy, which studies the structure of the internal organs.

The internal organs (viscera) are responsible for important functions of the organism: homeostasis, metabolism, water and gases turnover, excretion of metabolic products and reproduction.

Digestive systemDigestive system is the is the food processing system food processing system of human body. The of human body. The whole digestive system is whole digestive system is in the form of a long, in the form of a long, hollow, twisted and hollow, twisted and turned tube, called the turned tube, called the alimentary canal, which alimentary canal, which starts from the oral cavity starts from the oral cavity and ends at the anus. and ends at the anus. The overall process of The overall process of digestion and absorption digestion and absorption of food occurs in this of food occurs in this tube. The tube is divided tube. The tube is divided into different parts on the into different parts on the basis of structure and basis of structure and function of each part. function of each part.

ISCOMS – 2009ISCOMS – 2009 ISCOMS – International ISCOMS – International

Student Congress of Medical Student Congress of Medical Sciences – is one of the Sciences – is one of the world’s leading student world’s leading student conferences in the medical conferences in the medical sciences.sciences.

the University Medical Center of the University Medical Center of Groningen Groningen (the (the Netherlands ))   

With With Prof. Robin Warren Prof. Robin Warren MD PhD, Nobel Prize MD PhD, Nobel Prize laureate in 2005laureate in 2005

  hehe is credited with the 1979 re- is credited with the 1979 re-discovery of the discovery of the bacteriumHelicobacter pylori, together with , together with Barry Marshall. .

Necessary Organs Of the digestive system:Necessary Organs Of the digestive system: ORAL CAVITYORAL CAVITY ESOPHAGUSESOPHAGUS STOMACHSTOMACH SMALL INTESTINESMALL INTESTINE LARGE INTESTINELARGE INTESTINE ANUSANUS

Accessory Organs of the digestive system:Accessory Organs of the digestive system: LIVER AND GALL BLADDERLIVER AND GALL BLADDER PANCREASPANCREAS SALIVARY GLANDSSALIVARY GLANDS TEETHTEETH TONGUETONGUE

Functions of digestive system:Functions of digestive system: IngestionIngestion Digestion: break down of large particles of foodDigestion: break down of large particles of food

mechanical digestionmechanical digestion chemical digestionchemical digestion

Propulsion Propulsion peristalsisperistalsis segmentationsegmentation

Secretion: Secretion: digestive enzymesdigestive enzymes hormones hormones

Absorption:Absorption: from external environment into internal environmentfrom external environment into internal environment across mucosaacross mucosa

Elimination of wastes (defecation)Elimination of wastes (defecation)

Oral Cavity (mouth)Oral Cavity (mouth)

Entrance to the GI tract.Entrance to the GI tract. Initial site of digestion:Initial site of digestion:

mechanical digestion (via mastication)mechanical digestion (via mastication) chemical digestion (via enzymes in saliva).chemical digestion (via enzymes in saliva).

Bounded anteriorly by the teeth and lipsBounded anteriorly by the teeth and lips Bounded posteriorly by the oropharynx. Bounded posteriorly by the oropharynx. Superior boundary is formed by the hard Superior boundary is formed by the hard

and soft palates. and soft palates. Floor, or inferior surface, of the oral Floor, or inferior surface, of the oral

cavitycavity the tonguethe tongue

FaucesFauces represent the opening represent the opening between the oral cavity and the between the oral cavity and the oropharynx. oropharynx.

Fauces are bounded by paired Fauces are bounded by paired muscular folds:muscular folds: glossopalatine arch (anterior glossopalatine arch (anterior

fold) fold) pharyngopalatine arch (posterior pharyngopalatine arch (posterior

fold)fold) Palatine tonsils are housed Palatine tonsils are housed

between the arches.between the arches.

TeethTeeth Collectively known as the Collectively known as the dentitiondentition. . Responsible for Responsible for masticationmastication

first part of the mechanical digestion. first part of the mechanical digestion. A tooth has:A tooth has:

crowncrown neckneck one or more one or more rootsroots

Collectively, the roots, the dental Collectively, the roots, the dental alveoli, and the periodontal ligament alveoli, and the periodontal ligament that binds the roots to the alveolar that binds the roots to the alveolar processes form a processes form a gomphosisgomphosis joint. joint.

TOOTH TYPES ARE :TOOTH TYPES ARE :INCISORSINCISORSCANINECANINEPREMOLARSPREMOLARSMOLARSMOLARS

COMPONENTS OF THE TOOTH COMPONENTS OF THE TOOTH INCLUDE:INCLUDE:

ENAMELDENTINPULP CEMENTUM

20 deciduous teeth, also called “milk teeth,” erupt between 6 months and 30 months after birth.

These teeth are eventually lost and replaced by 32 permanent teeth.

THE LARGE THE LARGE SALIVARY GLANDSSALIVARY GLANDS ARE : ARE : PAROTIDPAROTID SUBMANDIBULARSUBMANDIBULAR SUBLINGUALSUBLINGUALGLANDS PRODUCE SEROUS AND MUCOSAL GLANDS PRODUCE SEROUS AND MUCOSAL

SECRETIONSSECRETIONS

Components of salivaComponents of saliva Water:Water: makes up 99% makes up 99% AmylaseAmylase: first step of chemical digestion: first step of chemical digestion LysozymeLysozyme: antimicrobial: antimicrobial

FunctionsFunctions Moisten foodMoisten food Food molecules into solution: tasteFood molecules into solution: taste Form bolus: for swallowingForm bolus: for swallowing Cleanse oral cavity.Cleanse oral cavity.

TONSILS INCLUDETONSILS INCLUDE : : PHARYNGEAL, PHARYNGEAL, PALATINE, LINGUALPALATINE, LINGUAL

THE THE PHARYNXPHARYNX INCLUDES :INCLUDES :

NASOPHARYNXNASOPHARYNX OROPHARYNXOROPHARYNX LARYNGOPHARYNXLARYNGOPHARYNX

SwallowingSwallowing

Swallowing involves Swallowing involves coordinated activity of coordinated activity of tongue, soft palate tongue, soft palate pharynx and oesophagus. pharynx and oesophagus.

The first (buccal) phase is The first (buccal) phase is voluntary, food being voluntary, food being forced into the pharynx by forced into the pharynx by the tongue.the tongue.

After this the process is After this the process is reflex. The tongue blocks reflex. The tongue blocks the mouth, soft palate the mouth, soft palate closes off the nose and closes off the nose and the larynx rises so that the larynx rises so that the epiglottis closes off the epiglottis closes off the trachea. Food thus the trachea. Food thus moves into the pharynx moves into the pharynx and onwards by peristalsis and onwards by peristalsis aided by gravity. aided by gravity.

If we try to talk whilst If we try to talk whilst swallowing food may swallowing food may enter the respiratory enter the respiratory passages and a cough passages and a cough reflex expels the bolus.reflex expels the bolus.

EsophagusEsophagus A straight muscular tube about A straight muscular tube about

25-30 cm long25-30 cm long It begins at the level of the It begins at the level of the

cricoid cartilage, inferior to the cricoid cartilage, inferior to the larnyx behind the trachea and larnyx behind the trachea and extends through the chest cavity, extends through the chest cavity, pierces the diaphragm at the pierces the diaphragm at the esophageal hiatus , and meets esophageal hiatus , and meets with the stomach at an opening with the stomach at an opening called the cardiac orifice. called the cardiac orifice.

It transports food to the stomach It transports food to the stomach and secretes mucus, which aids and secretes mucus, which aids transport.transport.

The inferior segment is The inferior segment is constricted forming the lower constricted forming the lower esophageal sphincter which, esophageal sphincter which, along with the diaphragm, closes along with the diaphragm, closes to prevent back flow of stomach to prevent back flow of stomach contentscontents

StomachStomach An enlarged segment of the An enlarged segment of the

tract that functions mainly tract that functions mainly in storing food and mixing in storing food and mixing it with gastric juice it with gastric juice (creating a paste called (creating a paste called chyme). chyme).

Other functions of stomach Other functions of stomach include: include:

Chemical digestion of Chemical digestion of proteinsproteins

Secretion of intrinsic factor Secretion of intrinsic factor – a chemical that is – a chemical that is necessary for vitamin B12 necessary for vitamin B12 absorption. absorption.

Destruction of ingested Destruction of ingested bacteria via secreted bacteria via secreted hydrochloric acid.hydrochloric acid.

Gross anatomyGross anatomy CardiaCardia

Cardiac orificeCardiac orifice FundusFundus BodyBody PylorusPylorus

Pyloric sphincterPyloric sphincter Pyloric orificePyloric orifice

Greater curvatureGreater curvature Greater omentumGreater omentum

Lesser curvatureLesser curvature Lesser omemtumLesser omemtum

THE WALL OF THE STOMACH THE WALL OF THE STOMACH INCLUDESINCLUDES : : EXTERNAL SEROSAEXTERNAL SEROSA MUSCLE LAYER ( CIRCULAR, MUSCLE LAYER ( CIRCULAR,

LONGITUDINAL, OBLIQUE )LONGITUDINAL, OBLIQUE ) SUBMUCOSASUBMUCOSA INTERIOR MUCOSALINTERIOR MUCOSAL

The mucous membrane The mucous membrane lining the stomach is lining the stomach is thick and vascular. It is thick and vascular. It is thrown into numerous thrown into numerous folds, known as rugae, folds, known as rugae, which are which are predominantly predominantly longitudinal in longitudinal in direction. On distention direction. On distention of the stomach, these of the stomach, these folds flatten out. It folds flatten out. It contains the glands contains the glands and the gastric pits.and the gastric pits.

GASTRIC PITS ARE THE GASTRIC PITS ARE THE OPENINGS INTO THE GASTRIC OPENINGS INTO THE GASTRIC GLANDSGLANDS

Mucous neck cellsMucous neck cells – found in – found in the upper portion of the gland. the upper portion of the gland. Secrete acidic mucus and Secrete acidic mucus and function as stem cells for function as stem cells for surface mucous cells. surface mucous cells.

Chief cellsChief cells – primary function – primary function is the secretion of pepsinogen, is the secretion of pepsinogen, an inactive form of the an inactive form of the protease, pepsin. Pepsinogen protease, pepsin. Pepsinogen is activated by HCl and by is activated by HCl and by pepsin itself. pepsin itself.

Parietal cellsParietal cells – found in the – found in the midportion of the glands. midportion of the glands. Secrete hydrochloric acid Secrete hydrochloric acid (which gives the stomach its (which gives the stomach its low pH – usually 1-3) as well as low pH – usually 1-3) as well as intrinsic factor. intrinsic factor.

Enteroendocrine cellsEnteroendocrine cells – – secrete multiple hormones secrete multiple hormones into the plasma. An example is into the plasma. An example is gastrin, a hormone that gastrin, a hormone that regulates the stomach’s regulates the stomach’s motility and secretory activity.motility and secretory activity.

Stomach has three main functions;Stomach has three main functions; Storage of food:Storage of food: It stores food for a  It stores food for a

variable amount of time (depending on the variable amount of time (depending on the nature of food) in order to make it nature of food) in order to make it appropriate for digestion and absorption in appropriate for digestion and absorption in the small intestine. The storing capacity of the small intestine. The storing capacity of stomach in an average adult is about 1500 stomach in an average adult is about 1500 ml.ml.

Mixing of food:Mixing of food: It mixes the food with its  It mixes the food with its own secretions (gastric secretions) to form a own secretions (gastric secretions) to form a semifluid chyme.semifluid chyme.

Controlling the rate of delivery of Controlling the rate of delivery of chyme:chyme:  The stomach also controls the rate The stomach also controls the rate of delivery of chyme to the small intestine so of delivery of chyme to the small intestine so that efficient digestion and absorption can that efficient digestion and absorption can take place.take place.

  

ThankThank you for attention!you for attention!