Anatomy and Physiology of the Digestive System: From Mouth to Stomach

Anatomy of the Digestive System Mouth The oral cavity is the entrance to the digestive system and contains accessory organs that function in the initial process of digestion. Consists of: 1. Lips 2. Cheeks 3. Tongue 4. Salivary glands 5. Teeth In the mouth there are additional organs in the form of the tongue, teeth and salivary glands. The lips consist of striated muscles namely the orbicularis oris and the cheeks consist of the main muscle. Tongue The tongue is a muscular structure located at the bottom of the mouth. The base of the tongue is attached to thehyoid boneAndfremulumon the floor of the mouth. The papillae contain sensory receptors (special nerve endings) which function as taste buds. There are three types of papillae vizvalate papillaewhich usually number 8-12 and are arranged in an inverted V shape at the base of the tongue and are the largest in size;fungiform papillaeis located at the tip of the tongue and is more numerous than the valate papillae; Andfliform papillaeare the smallest and most abundant papillae on the surface of the anterior two-thirds of the tongue. The tongue has 3 functions, namely: mastication (chewing), deglutition (swallowing) and taste (talking). Taste is felt by the taste organs located on the surface of the tongue. Taste is relatively simple, consisting of sweet, sour, salty and bitter. Salivary Glands In the oral cavity there are several salivary glands that pour their secretions directly into the mouth in the oral cavity, namely: 1.Labial glands 2.Buccal Glandula. 3.Molar Glandula 4. Palatine Glandula. 5.Lingual Glandula. There are 3 pairs of salivary glands, namely:Parotid Glandula is the largest gland found in the mouth and has a duct called Stensen's, Sub Maxillary glandis the second largest gland with its ducts called Wharton's, and Sublingual gland namely the smallest gland which is a collection of glands with two ducts. Saliva composition. Saliva mainly consists of serous secretions, which is 98% and contains the enzyme amylase and various types of ions (sodium, chloride, bicarbonate and potassium), as well as mucus secretions which are thicker and less containing glycoproteins (mucin), ions and water. Salivary function: 1. Saliva dissolves food chemically for taste. 2. Saliva moistens and lubricates food so it can be swallowed. 3. Amylase in saliva breaks down starch into polysaccharides and maltose, a disaccharide. 4. Waste substances such as uric acid and urea, as well as various other substances such as drugs, viruses and metals, are excreted into saliva. 5. Anti-bacterial substances and antibodies in saliva function to clean the oral cavity and help maintain oral health and prevent tooth decay. Tooth Teeth are attached to the alveoli or cavities at the base of the teeth of the mandible and maxilla. Humans have 2 sets of teeth: primary teeth (deciduous, milk teeth) and secondary (permanent) teeth. 1. The primary teeth in the half dental arch (starting from the space between the two front teeth) consist of two incisors, one canine, two molars, for a total of 20 teeth. 2. Secondary teeth begin to appear at the age of five to six years. Half of the dental arch consists of two incisors, one canine, two premolars (bicuspids), and three molars (tricuspids), for a total of 32 pieces. The third molars are called “wisdom teeth”. Food is cut into small pieces by the front teeth (incisors) and chewed by the back teeth (molars, molars), into small pieces that are more easily digested. Saliva from the salivary glands will coat parts of the food with digestive enzymes and begin to digest them. Saliva also contains antibodies and enzymes (e.g. lysozyme), which break down proteins and attack bacteria directly. Swallowing process starts consciously and continues automatically. Throat ( pharynx) It is a connection between the oral cavity and the esophagus. Derived from Greek, namely Pharynk. Consists of 3 parts, namely: 1.Pars Nasalisthe part that is parallel to the nose. In this section there arePharyngeal tonsils which in small children are called tonsils. 2.Pars Oralisnamely the part parallel to the mouth, on the side there isPalatine tonsils plays an important role in preventing the entry of germs through the mouth. 3.Pars Laryngea, on the front there isEpiglottiswhich functions to close the larynx during swallowing. Swallow (Deglutition). divided into three phases: a. Phasebuccaloccurs consciously in the mouth b. Phasepharynxoccurs involuntarily when food enters the pharynx c.Phase esofagusoccurs unconsciously in the esophagus. Esophagus The esophagus is a muscular tube, about 9 to 10 inches (25 cm) long and 1 inch (2.54 cm) in diameter. The esophagus moves food from the pharynx to the stomach through peristalsis. The esophagus does not produce digestive enzymes Stomach It is a wide, J-shaped part of the digestive tract located in the region epigastric, umbilicall and hypochondriac left abdominal cavity.The stomach consists of parts cardia, fundus,organ body, and partspilorus. The stomach functions as a food store, contracting rhythmically to mix food with enzymes. The stomach lining consists of 4 layers, namely the cells lining the stomach produce 3 important substances: 1. Mucosa layer, this layer is folded called rugae. There are 3 glands found in this mucosa layer, namely: a. GlandulaGastricaewhich produces Pepsan and HCl b. GlandulaCardiacwhich produces mucus c. GlandulaPyloricaeproduces pepsin 2. Sub Mucosa Layer: consists of connective tissue. 3. The Muscular Layer (muscle) consists of 3 layers, namely: Longitudinal, Cercular and Oblique Stratum. 4. Serous layer, which is found in Curvatura Minor is called Omentum Minus and which is found in Curvatura Major is called Omentum Mayus There are 3 phases in gastric secretion, namely: 1. PhaseCephalic: produces 10% of gastric secretions gastric juice flow 2. PhaseGastric/Hormonal: begins when food reaches the pyloric antrum producing 2/3 of gastric secretions (2000 ml/day). 3. PhaseIntestinal: when some of the digested stomach contents reach the small intestine. Gastric Function: 1. Temporary storage 2. Production of chyme 3. Protein digestion through the secretion of trypsin and hydrochloric acid 4. Production of mucus produced from glands to protect the stomach 5. Production of intrinsic factor a. Intrinsic factor is a glycoprotein secreted by parietal cells b. Vitamin B12. 6.Nutrient absorption that takes place in the stomach is only small