M9

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    What are the major organs of the alimentary tract?

    The major digestive organs include the mouth (oral cavity), pharynx, oesophagus, stomach, small intestine (duodenum, jejunum, ileum), and large intestine (caecum, appendix, colon, rectum, anal canal, anus).

    Describe the structure and function of the oral cavity.

    The oral cavity is bounded by the lips anteriorly, fauces posteriorly, and includes the vestibule and oral cavity proper. It is lined with moist non-keratinised stratified squamous epithelium and is involved in the initial stages of digestion, including mastication and mixing food with saliva.

    What are the muscles of mastication and their functions?

    The muscles of mastication include the masseter, temporalis, and medial and lateral pterygoids. They control the movements of the mandible for chewing, including elevation, depression, protraction, retraction, and lateral movements.

    How do salivary glands contribute to digestion?

    Salivary glands, including the parotid, submandibular, and sublingual glands, secrete saliva which contains enzymes that begin the digestion of carbohydrates, lubricates food for easier swallowing, and helps maintain oral health.

    Where do pancreatic secretions enter the digestive tract?

    Pancreatic secretions enter the digestive tract via the hepatopancreatic ampulla into the duodenum.

    What regulates the flow of pancreatic secretions into the digestive tract?

    The flow of pancreatic secretions is controlled by the ampullar sphincter, which opens in response to hormonal signals, particularly cholecystokinin.

    Explain the process of mastication.

    Mastication is the process of chewing food using teeth and muscles of mastication. It is reflexively controlled by the medulla but can be consciously overridden.

    What are the phases of swallowing (deglutition)?

    Swallowing consists of three phases: the voluntary phase where the tongue pushes the bolus to the pharynx, the pharyngeal phase which is reflexive and involves the elevation of the soft palate and closure of the airway, and the esophageal phase where peristalsis moves the bolus to the stomach.

    Define haustral contractions and their role in digestion.

    Haustral contractions are slow, segmenting movements in the large intestine that mix and move contents, aiding in absorption and the formation of feces.

    What is the purpose of segmentation in the digestive process?

    Segmentation is a process that mixes intestinal contents, enhancing nutrient absorption by increasing contact with the intestinal wall.

    Name the three major salivary glands and their secretions.

    The three major salivary glands are the parotid (largest, serous secretion), submandibular (mixed, mostly serous), and sublingual (smallest, mostly mucous).

    Describe the structure and function of the liver.

    The liver has four lobes (left, right, caudate, quadrate) and functions to produce bile, process nutrients, and detoxify blood. Its histology includes lobules with portal triads and central veins.

    What structures are found at the porta hepatis?

    At the porta hepatis, the entering structures include the hepatic portal vein, hepatic artery, and hepatic nerve plexus, while exiting structures include lymphatic vessels and hepatic ducts.

    What comprises a portal triad in the liver?

    A portal triad consists of the hepatic portal vein, hepatic artery, and hepatic duct, found at the corners of liver lobules, with a central vein located in the middle.

    Describe the flow of blood through the liver.

    Blood flows from the portal vein and hepatic artery into the sinusoids, then to the central vein, and finally into the hepatic veins which drain into the inferior vena cava (IVC).

    How is bile produced and transported in the liver?

    Bile is produced by hepatocytes, flows into bile canaliculi, then into hepatic ducts, and finally into the common bile duct for transport to the duodenum.

    What is the role of the gallbladder in digestion?

    The gallbladder stores and concentrates bile, releasing it via the cystic duct into the common bile duct, stimulated by cholecystokinin and vagal stimulation.

    What is the structure and function of the exocrine pancreas?

    The exocrine pancreas is composed of acini (grape-like clusters) that form lobules and secrete digestive enzymes into ducts that lead to the duodenum.

    How do reflex and voluntary control interact in swallowing?

    In swallowing, the voluntary phase involves conscious control by the tongue, while the pharyngeal and esophageal phases are reflexive, coordinated by the medulla.

    What are mass movements in the large intestine?

    Mass movements are powerful contractions in the large intestine that propel contents toward the rectum, facilitating the elimination of waste.

    What is the significance of the anal canal and anus in digestion?

    The anal canal and anus are the final parts of the digestive tract, responsible for the controlled expulsion of feces from the body, regulated by internal and external anal sphincters.