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Digestive System Notes
Bsc nursing (blaw 213)
Kerala University of Health Sciences
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DIGESTIVE SYSTEM
PROCESS OF DIGESTION
- Ingestion
- Digestion
- Absorption
- Excretion Ingestion
- Ingestion or taking in of food and mastication, performed by mouth and teeth, aided by tongue. Pharynx and oesophagus are concerned with swallowing Digestion
- It occurs in the stomach and upper part of the small intestine Absorption
- It can occur from any part of the alimentary canal Excretion
- Large intestine absorbs major quantity of water and the residue is excreted in the form of feces
PROCESS OF DIGESTION - Mouth Pharynx Oesophagus Stomach Fundus Duodenum Jejunum Ileum Cecum and appendix ascending colon transverse colon descending colon sigmoid colon rectum anal canal Functions Of The Digestive System - Ingestion – taking food and liquid into the mouth - Secretion – total 7 liter into the lumen - Mixing and propulsion – through the GI muscles, peristalsis and motility - Digestion – breakdown of ingested food
Absorption – passage of nutrients into the blood
Metabolism – production of cellular energy (ATP)
Defecation – waste substances leave the GI tract through anus Organs of digestive system Two main groups Alimentary canal or GI tract Accessory digestive organs
Teeth
Tongue
Salivary gland
Liver
Gall bladder
pancreas Mouth / oral cavity
It is the first part of the digestive tube Divided in to two Mouth proper/oral cavity proper VESTIBULE
Vestibule is a slit like space between the lips and cheeks externally, and gums and teeth internally
Parotid duct opens into the vestibule
Epithelial lining is by stratified squamous non keratinizing
Numerous mucous glands, buccal and labial open into vestibule LIPS /LABIA
They are the fleshy folds lined externally by skin and internally by mucous membrane CHEEKS
They are the fleshy flaps forming the larger part of each side of the face
Premolars – 4
Molars (grinders) - 6 STRUCTURE OF TOOTH
Tooth is composed of dentine
At the crown dentine is covered by enamel, and at the root by cementum
Enamel – It is the hard covering on the exposed part of the tooth
Cementum - Thin layer of bonelike material covering the roots
Dentine – it is the middle layer of tooth. It is a yellowish tissue which is harder than bone and softer than enamel. Dentine is covered by enamel over the crown and cementum over the root
Pulp cavity /tooth cavity– it is the centre of the tooth, contains connective tissues, blood vessels and nerves
Root canal – Narrow tunnel for the blood vessels and nerves to enter pulp
Blood supply
Arterial supply
- Maxillary artery
Venous supply – Pterygoid venous plexus
Lymphatic drainage – Submandibular nodes
Nerve supply – Upper jaw by maxillary nerve
- Lower jaw by inferior alveolar nerve (branch of mandibular nerve) PALATE
It forms the arched roof of the oral cavity and the floor of the nasal cavities Parts Two regions
Anterior two third, the bony part – hard palate
Posterior one third – fibromuscular part – soft palate HARD PALATE
Formed by palatine processes of maxillae and horizontal processes of palatine bones
It is the partition between the nasal and oral cavities
It is covered by mucous membrane that is firmly attached to the bone SOFT PALATE
It is attached to the posterior edge of the hard palate
It is a movable fibromuscular fold
It has conical process called uvula MUSCLES OF SOFT PALATE
Five pairs of muscles
Levator palati
Tensor palati
Palatoglossus
Palatopharyngeus
Musculus uvulae
A V shaped groove - the sulcus terminalis divides the surface into palatine part and pharyngeal part
Apex of the V is – Foramen cecum
A shallow median groove extends from the tip to the foramen cecum divides the anterior 2/3rd into right and left halves
The anterior two third of the dorsum of the tongue is rough due to the presence of microscopic projections called papillae TYPES OF PAPILLAE Filiform
Conical, most numerous, occur throughout the anterior two third Fungiform
Red, mushroom shaped, scattered, provided with taste buds Circumvallate or vallate
Large, drum shaped papillae, easily seen with naked eye, 8-12 in number, arranged anterior to sulcus terminalis
Taste buds are present in circumvallate papillae Foliate papillae :
Located on the sides of the tongue, they also have taste receptors located in taste buds VENTRAL SURFACE
Covered by smooth mucous membrane
There is a median mucous fold called frenulum linguae
On either side of the frenulum deep lingual vein can be seen
Muscles of tongue Intrinsic muscles - Superior longitudinal muscle – tip and side of the tongue and shortens the tongue - Inferior longitudinal muscle – curls the tip of the tongue downwards and shortens the tongue - Transverse muscle – narrows and elongates the tongue - Vertical muscle – flattens and broadens the tongue Extrinsic muscles - Genioglossus – contributes most bulk of the tongue - Hyoglossus – helps to pull the tongue back into the tongue - Styloglossus – helping to swallow the bolus - Palatoglossus – helps to elevate the back portion of the tongue
- They are small barrel shaped structures arranged along the sides of the grooves that surround the vallate and fungiform papillae
- It has layered appearance like an onion
- There are two types of cells in the taste buds, ie. Sustentacular cells(supporting) and neuroepithelial nerve cells
- The tasted substances get dissolved in the saliva and passes through the taste pore into the pit of the taste bud, where it stimulates the hairs of neuroepithelial cells SALIVARY GLANDS
- They make saliva, helps in digestion, and helps to keep the mouth moist and supports healthy teeth
- They are classified into two
- Major and minor salivary glands Major Salivary Glands
- The major salivary glands are the largest and most important salivary glands. They produce most of the saliva in mouth. They discharge their secretions into the mouth through a duct
- There are three pairs of major salivary glands: the parotid glands, the submandibular glands, and the sublingual glands Minor Salivary Glands
- There are hundreds of minor salivary glands throughout the mouth and the aerodigestive tract. They directly pour their secretions into the oral cavity
- These glands are too small to be seen without a microscope.
- Most are found in the lining of the lips, the tongue, and the roof of the mouth, as well as inside the cheeks, nose, sinuses, and larynx (voice box) MAJOR SALIVARY GLANDS
- Parotid gland
- Submandibular
- Sublingual
PAROTID GLAND
- The parotid glands are the largest salivary glands.
- They are paired glands
- They are located just in front of the ears.
- The saliva produced in these glands is secreted into the mouth from a duct near the upper second molar.
- It is an irregular, lobulated, yellowish mass covered by fibrous capsule
- Parotid duct or Stenson's duct passes horizontally from the anterior edge of the gland. It is about 5cm long and 5mm in diameter Major structures in relations are
- External carotid artery
- Retromandibular vein – at the lower border of the gland
- Facial nerve
- Parotid lymph nodes ARTERIAL SUPPLY External carotid artery NERVE SUPPLY Sympathetic and parasympathetic nerve fibers APPLIED ANATOMY
- Mumps - it is an infectious disease caused by mumps virus, affects the parotid gland
- Parotidectomy is the surgical removal of the parotid gland
- Parotid gland tumor - it can affect the facial nerve, resulting in paralysis of the facial expression on that side SUBMANDIBULAR GLAND
- It is a large salivary gland, roughly J shaped, located below the jaw, in the digastric triangle.
OESOPHAGUS
- The oesophagus is a narrow muscular tube, forming the food passage between the pharynx and stomach.
- It extends from the lower part of the neck to the upper part of the abdomen.
- It is about 25 cm long.
- Diameter is 1 PARTS
- CERVICAL
- THORACIC
- ABDOMINAL Cervical
- Cervical begins at the lower end of pharynx (level of 6th vertebra or lower border of cricoid cartilage) and extends to the thoracic inlet (suprasternal notch); 18 cm from incisors. Thoracic
- Upper thoracic: from thoracic inlet to level of tracheal bifurcation; 18- cm.
- Mid thoracic: from tracheal bifurcation midway to gastroesophageal junction; 24-32 cm.
- Lower thoracic: from midway between tracheal bifurcation to GE junction, including abdominal oesophagus; 32-40 cm. Abdominal part
- Considered part of lower thoracic esophagus; 32-40 cm. CONSTRICTIONS OF OESOPHAGUS Oesophagus has 4 constrictions
At the pharyngoesophageal junction
At the point where it is crossed by the arch of aorta
At a point where it is crossed by the left bronchus
At a point where it passes through the diaphragm IMORTANT RELATIONS CERVICAL PART Posteriorly – Vertebral column Laterally – Carotid sheath and its content Anteriorly – Trachea Between trachea and oesophagus – Recurrent laryngeal nerve THORACIC PART Posteriorly - vertebral column Anteriorly from above down wards
Trachea
Left bronchus
Right pulmonary artery
Left atrium
Diaphragm On either side – mediastinal pleura of the lungs ABDOMINAL PART
- It is a short segment of the oesophagus lies in a groove of the posterior surface of the left lobe of liver BLOOD SUPPLY
- By the oesophageal branches of the descending thoracic aorta and oesophageal branches of the left gastric artery VENOUS DRINAGE
- From the upper part – into the azygos venous system
- Lower part – into the left gastric vein- into portal vein NERVE SUPPLY
Radiological anatomy - Barium swallow REGIONS OF THE ABDOMEN Mainly two types of classification 4 region scheme and 9 region scheme 1. 4 Region Scheme In four region scheme there is one vertical plane through the Linea alba which crosses the horizontal line through the umbilicus and forms 4 quadrants as - Right Upper Quadrant - Right Lower Quadrant - Left Upper Quadrant - Left Lower Quadrant 2. 9 Region Scheme - Abdominal cavity is divided into 9 regions by two lateral vertical planes (mid clavicular or mid inguinal plane) and two horizontal planes (transpyloric and transtubercular plane) - Trans tubercular plane – Passes through the iliac tubercles on the iliac crest - Transpyloric plane – Imaginary axial plane located in the midway between the jugular notch and superior border of pubic symphysis - Mid clavicular line – Plane extending from the clavicle to the mid inguinal point The nine regions are - Epigastric or epigastrium - Right hypochondrium - Left hypochondrium - Umbilical - Right lumbar - Left lumbar - Suprapubic or hypogastrium
- Right iliac fossa or right inguinal region
- Left iliac fossa or left inguinal region
STOMACH
The stomach, is an intraperitoneal digestive organ located between the oesophagus and the duodenum
It extends from the cardiac end to the pyloric end
Upper end continuous with the oesophagus and lower end is with the duodenum POSITION
It occupies epigastric, umbilical and left hypochondriac regions SHAPE
It is J shaped, upper part is broader than the lower part
It has two ends- upper cardiac and lower pyloric
Two surfaces- anterior and posterior
Two borders or curvatures – right border or lesser curvature and left border or greater curvature CAPACITY
Newborn infants stomach – 30ml,
At puberty – 1 liter
Adult – 1-2liter FUNCTIONS
Reservoir of food
Peristaltic activity helps to mix the food with gastric juice
Gastric enzymes helps in digestion
HCL present in the gastric gland helps to destroy many organisms present in food and drink
Stomach secretes the intrinsic factor that is necessary for the absorption of vitamin B
Lesser curvature/right border – forms the shorter, concave, medial surface of the stomach.
The most inferior part of the lesser curvature, the angular notch, indicates the junction of the body and pyloric region.
The lesser curvature gives attachment to the hepatogastric ligament and is supplied by the left gastric artery and right gastric branch of the hepatic artery. Greater and Lesser Omentum
Within the abdominal cavity, a double layered membrane called the peritoneum. supports most of the abdominal viscera and assists with their attachment to the abdominal wall.
The greater and lesser omenta are two structures that consist of peritoneum folded over itself (two layers of peritoneum – four membrane layers). Both omenta attach to the stomach, and are useful anatomical landmarks:
Greater omentum – hangs down from the greater curvature of the stomach and folds back upon itself where it attaches to the transverse colon It contains many lymph nodes and, therefore playing a key role in gastrointestinal immunity and minimizing the spread of intraperitoneal infections.
Lesser omentum – continuous with peritoneal layers of the stomach and duodenum, this smaller peritoneal fold arises at the lesser curvature and ascend to attach to the liver. The main function of the lesser omentum is to attach the stomach and duodenum to the liver. Relations of the anterior surface
Left lobe of liver
Diaphragm
Anterior abdominal wall Relations of the posterior surface
It is the stomach bed - Structures related are
Anterior surface of pancreas
Transverse mesocolon and transverse colon
Anterior surface of the upper part of left kidney
Left supra renal
Splenic artery
Diaphragm
Gastric surface of spleen
Blood supply - arterial supply
Left gastric artery – a branch of celiac trunk
Right gastric artery- branch of hepatic artery, runs along the lesser curvature
Left gastroepiploic artery – a branch of gastro duodenal artery, it goes along the greater curvature and anastomoses with gastroepiploic artery
Short gastric arteries - 5-6 in number, arise from the splenic artery, and supply the fundus of the stomach VENOUS DRAINAGE
Right and left gastric veins – end in portal vein
Short gastric and left gastroepiploic veins drain into splenic veins
Right gastroepiploic vein drain into superior mesenteric vein
Prepyloric vein
LYMPHATIC DRAINAGE
Into the celiac nodes
NERVE SUPPLY
Parasympathetic from vagus nerves and sympathetic from celiac plexus Histology
- MUCOSA
Very thick, lined by simple columnar epithelium
Beneath the epithelium, -connective tissue layer- lamina propria, lamina muscularis, they contain gastric gland
Ducts opens into the lumen of the stomach
Digestive System Notes
Course: Bsc nursing (blaw 213)
University: Kerala University of Health Sciences
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