Gastrointestinal Tract (GIT)//DIGESTIVE SYSTEM
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The document provides a comprehensive overview of the digestive system, also known as the gastrointestinal system, detailing its structure and functions. It outlines the parts of the alimentary canal, including the mouth, pharynx, oesophagus, stomach, small intestine, and large intestine, along with their specific roles in digestion and nutrient absorption. Additionally, it discusses the layers of the alimentary canal wall and the function of associated digestive glands.
Gastrointestinal Tract (GIT)//DIGESTIVE SYSTEM
- 1. THE DIGESTIVE SYSTEM Represented by WASIM AKRAM BSc(N) ADWIKA INSTITUTE OF NURSING
- 2. CONTENTS INTRODUCTION FUCTIONS OF GI SYSTEM ALIMENTARY CANAL 1. MOUTH 2. PHARYNX 3. OESOPHAGUS 4. STOMACH 5. SMALL INTESTINE 6. LARGE INTESTINE COVERINGS OF ALIMENTARY CANAL
- 3. INTRODUCTION The Digestive System is also known as the Gastrointestinal System. It is the route through which Nutritive substances , vitamins , minerals and fluids enter in the body . The digestive system describes the Alimentary Canal , it’s accessory organs , glands and a variety of digestive processes that prepare food eaten in the diet for absorption. The activities of the Digestive System can be grouped under five main headings : 1) INGESTION 4) ABSORPTION 2) PROPULSION 5) ELIMINATION. 3) DIGESTION
- 4. FUNCTIONS OF GI SYSTEM 1) SECRETION OF DIGESTIVE JUICES 2) DIGESTION OF FOODS 3) ABSORPTION 4) MOVEMENTS OF FOODS 5) PROTECTION 6) ELIMINATION OF WASTE PRODUCTS.
- 5. PARTS OF GI SYSTEM The digestive system is composed of A. ALIMENTARY CANAL B. DIGESTIVE GLANDS ∆ ALIMENTARY CANAL: •It is also known as the GASTROINTESTINAL TRACT (GIT) . •It is essentially a long tube through which food passes. •It commences at the mouth and terminates at the anus. •In adults, it is around 5 meters in length. •PARTS OF GIT: - Mouth. - Stomach - Pharynx. - Small Intestine - Oesophagus. - Large Intestine.
- 6. MOUTH • Mouth is the beginning part of the Gastrointestinal System. • Mouth contains two parts : a) Vestibule b) Oral Cavity a) Vestibule: It is the cavity bounded by lips and cheeks , gums & teeth. b) Oral Cavity: > It is the cavity ( also known as Buccal Cavity ) bounded Laterally by maxillary bone & Teeth Superiorly by Palate Inferiorly by Tongue & soft tissues of floor of the mouth Posteriorly it is continuous with Oropharynx. > The oral cavity is lined with mucous membranes, consisting of stratified squamous epithelium containing small mucus secreting glands.
- 7. >PALATE: The palate forms the roof of the mouth and is divided into the ANTERIOR HARD PALATE and the POSTERIOR SOFT PALATE. ~ The hard palate is formed by the Maxilla and the Palatine bones . ~ The soft palate extends posteriorly and forms the UVULA. ~ During swallowing, uvula enclose the Nasopharynx to prevent the entry of food into the nasal cavity . >TONGUE: The tongue is composed of voluntary muscle. ~ It is a freely movable organ attached to HYOID BONE (posteriorly) and It is attached to the floor of the oral cavity by LINGUAL FRENULUM . ~ On the surface of the tongue , many small projections are present. These are called as PAPILLAE . ~ Tastes on the tongue : •Front – Sweet •Backside – Bitter •Besides – Sour •Middle - Salt
- 8. > TEETH: Human teeth are embedded in the sockets of the mandible & maxilla ( Jaw). ~ Human teeth are # Thecodont- Teeth are embedded in the socket of jaw bone. # Diphyodont- Human teeth are diphyodont with respect to tweenty teeth. # Heterodont- Four different type of adult teeth: Incisors (I), Canine (C), Premolar (PM), Molar (M). ~ Milk Teeth / Deciduous Teeth: 20 in number : 2102/2102 ; it is the dentition of the child teeth upto 6 years . Adult teeth / Permanent teeth : 32 in number : I/I, C/C, PM/PM, M/M = 2/2, 1/1, 2/2, 3/3 . * The third molar ( wisdom teeth ) are the last to erupt . * Monophyodont teeth of human – Premolar teeth. ~ Origin of teeth is Ectomesodermal . Enamel ( Ectodermal)- secreted from Ameloblast Cells. Dentine (Mesodermal)- secreted from Odontoblast Cells. * Enamel is the hardest part of the body ( Calcium Salts ). ~ The main function of the teeth are Chewing and Mastication of Food .
- 9. ~ Blood supply: Branches of Maxillary Arteries & Bunch of veins empty into the Internal Jugular veins. ~ Nerve supply: Branches of Trigeminal Nerves.
- 10. PHARYNX • It is the common passage for food and air. • The pharynx is divided into three parts : i) The Nasopharynx is important for respiration . ii) The Oropharynx continuous with oesophagus . iii) The Laryngopharynx continuous with trachea . * Epiglottis is a thin , elastic , cartilaginous flap whuich prevent the entry of food into the glottis . • Tonsils – These are lymphoid organ present in both side of the Uvula . ~ They are 4 in number and form a ring like structure known as the waldeyer’s ring . Pharyngeal, Tubeal, Palatine & Lingual tonsil . ~ Tonsils helps in 'First Line of Defence’ by secreting IgA . ~ Tonsillitis ~ Tonsillectomy
- 11. • Blood Supply: ~ Arterial Supply : Several branches of the Facial Arteries . ~ Venous Drainage : The facial veins & the Internal Jugular veins . • Nerve Supply: The pharynx is controlled by the ANS. ~ Parasympathetic supply is mainly by the Glossopharyngeal & Vagus nerves . ~ Sympathetic supply is from the Cervical Ganglia .
- 12. OESOPHAGUS • It is a thin , long tube which extends posteriorly passing through the neck , thorax , and diaphragm and it leads to the stomach . • It is about 25cm long and about 2cm in diameter. • It lies in the median plane in the thorax in front of the vertibral column and behind the trachea and the heart. • It passes between muscles fibres of the diaphragm behind the central tendon at the level of the 10th Thoracic Vertibra. • It’s opening into the the stomach is regulated by Cardiac Sphincter / Gastro-oeso phageal Sphincter. • During transport of food – Peristalsis ( Successive waves of muscular contraction ). • During vomitting – Reverse Peristalsis .
- 13. STOMACH • THE STOMACH IS A J-SHAPED BAG-LIKE DIALATED PORTION OF THE ALIMENTARY CANAL. • IT IS LOCATED IN THE UPPER LEFT PORTION ( EPIGASTRIC , UMBILICAL & LEFT HYPOCHON- DRIAC REGION ) OF THE ABDOMINAL CAVITY. • ORGANS ASSOCOATED WITH THE STOMACH: >ANTERIORLY- Left lobe of liver & anterior abdominal wall. >POSTERIORLY- Abdominal aorta, Pancreas, Spleen, left kidney & adrenal gland. >SUPERIORLY- Diaphragm, Oesophagus & left lobe of liver. >INFERIORLY- Transverse colon and small intestine. >TO THE LEFT- Diaphragm and Spleen. >TO THE RIGHT- Liver and Duodenum.
- 14. • PARTS OF STOMACH: The stomach is divided into four regions – i) Cardiac region: Oesophagus open into cardiac region and it is guarded by cardiac sphincter . ii) Fundic region: Secretory cells are present at this region . iii) Body/ corpus region : It is the largest section of our stomach . This region contracts and begins to mix food . iv) Pyloric region : Last part of stomach which opens into the first part of small intestine ( duodenum ) . Sphincter between pyloric portion and duodenum is known as Pyloric Sphincter . Gastric Rugae : Some irregular folds or Rugae on the innerline of stomach .
- 15. SMALL INTESTINE Small intestine is distinguishable into three regions – 1. DUODENUM : Smallest part of small intestine ( 25 – 30 cm ) . C shaped . No villi are present . Brunner’s glands releases mucus . Maximum digestion takes place here . Fe absorption take place here . 2. JEJUNUM : A long coiled middle portion ( 2 – 3 m ) . Fold of kerkring or plicae circularis => circular folds on mucosal layer . Villi present here => site of absorption . 3. ILEUM : Highly coiled and largest part of small intestine ( 3 – 4 m ) . LYMPHOID organ – Payer’s patch (secondary lymphoid organ) :- defence . Ileum opens into large intestine and guarded by Ileo-caecal valve . Villi : These are small finger like foldings ; site of absorption .
- 16. LARGE INTESTINE It consists four parts – 1. CAECUM : A small blind sac which hosts some symbiotic bacteria ( micro-organisms ) . Eg : Escherichia coli - helps in Vitamin B12 synthesis . A narrow finger like tubular projection called Vermiformed Appendix ( vestigial organ ) arises from CAECUM . 2. COLON : Caecum opens into colon . Colon divided into four parts – Ascending colon , Transverse colon , Descending colon and Sygmoid/Pelvic colon . 3. RECTUM : Storage of caecum . 4. ANAL CANAL : Blood capillaries are present around anal canal . Swelling of piles – Haemorrhoids . Anal opening is Anus and controlled by voluntary anal sphincter .
- 17. COVERING OF ALIMENTARY CANAL The wall of alimentary canal from oesophagus to rectum possesses four layers: 1. SEROSA : Outermost layer . Made up of a thin mesothelium with some connective tissues . Nerves and blood vessels are present in it . 2. MUSCULARIS : Formed by smooth muscles . Usually arranged into Inner circular layer and outer longitudinal layer . 3. SUB-MUCOSA: Formed of loose connective tissues containing nerves, blood and lymph vessels . In duodenum , glands ( Brunner’s glands ) are also present in sub-mucosa layer . 4. MUCOSA : The innermost layer lining the lumen of the alimentary canal . In stomach : Rugae ; in small intestine : Villi . Cells lining the villi – produce numerous microscopic projections called Microvilli giving a Brush Border appearance . Lacteals : a network of capillaries and a large lymph vessel . Helps in Fat Absorption .