Lecture 7 - Digestive System - First Year - AlMustafa University - PDF

AlMustafa University - School of Pharmacy - First year Human Biology lecture no. 7 – by Dr. Ali Yousif Al-Taei First Year - Biology lecture 7 – Pharmacy School – Dr. Ali Yousif Human body organ systems Eleven body organ systems work...

AlMustafa University - School of Pharmacy - First year Human Biology lecture no. 7 – by Dr. Ali Yousif Al-Taei First Year - Biology lecture 7 – Pharmacy School – Dr. Ali Yousif Human body organ systems Eleven body organ systems work together to maintain homeostasis and carry out life tasks; these are: 1. Digestive organ system 2. Endocrine organ system 3. Reproductive organ system 4. Integumentary organ system 5. Respiratory organ system 6. Urinary organ system 7. Cardiovascular organ system 8. Lymphatic organ system 9. Skeletal organ system 10. Muscular organ system 11. Nervous organ system Note 1: It is worth studying the biology of the first 8 organ systems in this first course of study, while studying the detailed anatomy of the skeletal, muscular, and nervous organ systems is more beneficial to be done in the second course of this year. Note 2: Homeostasis is a healthy status that is maintained by a proper functioning of cells, tissues, and organs allowing the human to regulate the stability and constancy needed for life. Homeostasis involves a constant adjustment of biochemical and physiological pathways. An example of homeostasis is the maintenance of a constant blood pressure in the human body through a series of fine adjustments in the normal range of function of the hormonal (endocrine), neuromuscular, and cardiovascular systems. 1  AlMustafa University - School of Pharmacy - First year Human Biology lecture no. 7 – by Dr. Ali Yousif Al-Taei First Year - Biology lecture 7 – Pharmacy School – Dr. Ali Yousif 2  AlMustafa University - School of Pharmacy - First year Human Biology lecture no. 7 – by Dr. Ali Yousif Al-Taei First Year - Biology lecture 7 – Pharmacy School – Dr. Ali Yousif 3  AlMustafa University - School of Pharmacy - First year Human Biology lecture no. 7 – by Dr. Ali Yousif Al-Taei First Year - Biology lecture 7 – Pharmacy School – Dr. Ali Yousif First organ system: Digestive system Overview: The digestive system is made up of a group of organs that all work together to perform the process of digestion by converting food into basic nutrients to feed/nourish the cells of the body. The full process of digestion requires ingestion, digestion, movement, absorption, and elimination steps. The entire digestive process takes between 24 and 33 hours. The digestive system works by breaking down food particles (mainly carbohydrates, fats and proteins) into simpler molecules that can be absorbed by the small intestine & carried to the liver by the blood for further processing. After processing by the liver, simple nutrition molecules are distributed to the whole body via the cardiovascular organ system. Digestive system is constituted by the gastrointestinal tract (GIT) portions in addition to the accessary organs that all carry out several processes to digest food. Two forms of digestion is available: mechanical and chemical. Mechanical digestion is done throughout chewing (churning), while chemical digestion involves adding enzymes such as the ones found in saliva or adding gastric acid produced by the stomach cells to the digested food. A- Gastrointestinal tract [GIT] (also called alimentary canal): The GIT is a long hollow tube with two ends. It runs from the mouth down through to the anus. The canal consists mainly of mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum and anus \ anorectal canal. B- Accessory organs: These are organs attached to the GIT that contribute to the food processing and assisting the alimentary canal to complete the process of food digestion. Accessory organs include the teeth, tongue, salivary glands, liver, gallbladder, and pancreas. 4  AlMustafa University - School of Pharmacy - First year Human Biology lecture no. 7 – by Dr. Ali Yousif Al-Taei First Year - Biology lecture 7 – Pharmacy School – Dr. Ali Yousif A- Portions (components) of the alimentary canal: 1- Mouth (also called the ‘oral cavity’ or the ‘buccal cavity’): The mouth is the first portion of the alimentary canal that receives food and produces saliva. It is mainly formed by the lips, cheeks, hard and soft palate, uvula, and the gum. 5  AlMustafa University - School of Pharmacy - First year Human Biology lecture no. 7 – by Dr. Ali Yousif Al-Taei First Year - Biology lecture 7 – Pharmacy School – Dr. Ali Yousif Parts of the oral cavity: - Lips (also called labia; singular; labium) – protect the anterior opening of the oral cavity. - Cheeks – form the lateral walls. - Hard palate ‫ – حنك صلب‬the bony front portion of the roof of mouth. - Soft palate ‫ – حنك رخو‬the muscular posterior portion of the roof of mouth. - Uvula ‫ – لهاة نازلة‬fleshy projection of the soft palate that has a function of blocking the internal nares (the inside openings of the nose) during swallowing. - Gum (also called gingiva; plural; gingivae) - mucosal tissue that lies over the mandible and maxilla inside the mouth and surrounds the teeth. Note: The vestibule is a apace between lips externally and teeth and gum enternally. The oral frenulum is a small piece of connective tissue that joins lips to gums (superior or inferior labial frenulum), or tongue to the floor of the mouth (lingual frenulum). 6  AlMustafa University - School of Pharmacy - First year Human Biology lecture no. 7 – by Dr. Ali Yousif Al-Taei First Year - Biology lecture 7 – Pharmacy School – Dr. Ali Yousif 2- Pharynx ‫البلعوم‬ The pharynx is a funnel-shaped tube that extends from the internal nares ‫ مناخر انفية‬to the esophagus and the larynx; i.e. the larynx ‫ حنجرة‬is anterior to the pharynx and the esophagus is posterior to the pharynx. Pharynx is a part of the throat ‫حلق‬. Uvula 7  AlMustafa University - School of Pharmacy - First year Human Biology lecture no. 7 – by Dr. Ali Yousif Al-Taei First Year - Biology lecture 7 – Pharmacy School – Dr. Ali Yousif Three portions of pharynx: - Nasopharynx – - Oropharynx – - Laryngopharynx – below the oropharynx and connected to the esophagus 3- Throat ‫الحلق‬ The throat is a respiratory space that includes the followings: - Pharynx ‫البلعوم‬. - Epiglottis ‫ لسان المزمار‬: a small flap that closes the opening of the respiratory system and particularly the trachea ‫ القصبة الهوائية‬when swallowing, preventing food from entering the airway and causing suffocation ‫االختناق‬. - Larynx (also called ‘voice box’) ‫ الحنجرة‬. 8  AlMustafa University - School of Pharmacy - First year Human Biology lecture no. 7 – by Dr. Ali Yousif Al-Taei First Year - Biology lecture 7 – Pharmacy School – Dr. Ali Yousif 4- Esophagus Is a muscular tube connecting the laryngopharynx (by the upper esophageal sphincter) with the stomach (by the lower esophageal sphincter). Esophagus conducts food by peristalsis (slow rhythmic squeezing). 9  AlMustafa University - School of Pharmacy - First year Human Biology lecture no. 7 – by Dr. Ali Yousif Al-Taei First Year - Biology lecture 7 – Pharmacy School – Dr. Ali Yousif The esophagus is posterior to the larynx and trachea in the neck region and upper thorax. It passes through the diaphragm ‫الحجاب الحاجز التنفسي‬, and connects with the stomach. 5- Stomach The stomach is a J shaped expanded bag, located on the left side of the abdomen. By other means, it is located in the left upper quadrant of the abdominal cavity. It is anterior to the spleen. There are 4 regions of the stomach; cardiac region, fundus region, body region (the largest region), and the pylorus region. Note: Gastric (digested food) contents are expelled into the proximal duodenum via relaxing the pyloric sphincter. 10  AlMustafa University - School of Pharmacy - First year Human Biology lecture no. 7 – by Dr. Ali Yousif Al-Taei First Year - Biology lecture 7 – Pharmacy School – Dr. Ali Yousif 6- Small intestine (also called ‘small bowel’ or ‘gut’) It’s the major digestive organ of the body with average length of 6 meters and 2.5 cm diameter. It’s a muscular tube extending from the pyloric sphincter at the end of the stomach till the ileocecal valve. The chemical digestion of food is completed in the small intestine with the help of enzymes secreted by the liver and pancreas and absorption of digested food into the blood or lymph occurs by the villus. The villi (plural: Villus) is a little projection in the lining of the small intestine that functions in the absorption of ongoing digested food. The small intestine is compressed into numerous folds and occupies a large proportion of the abdominal cavity. It is composed of three portions; the duodenum, jejunum, and the ileum. The first portion of the gut is the duodenum which is a C-shaped section that curves around the head of the pancreas. The duodenum serves a mixing function as it combines digestive secretions from the pancreas and liver with the contents expelled from the stomach. The second part of the small intestine is the jejunum where the majority of digestion and absorption occurs. The final portion, the ileum, is the longest segment of the small bowel which empties the contents into the caecum at the ileocecal junction controlled by the ileocecal valve. 11  AlMustafa University - School of Pharmacy - First year Human Biology lecture no. 7 – by Dr. Ali Yousif Al-Taei First Year - Biology lecture 7 – Pharmacy School – Dr. Ali Yousif 12  AlMustafa University - School of Pharmacy - First year Human Biology lecture no. 7 – by Dr. Ali Yousif Al-Taei First Year - Biology lecture 7 – Pharmacy School – Dr. Ali Yousif 7- Large intestine (also called ‘large bowel’ or the ‘colon’) The large intestine is like a horse-shoe in shape and extends around the small intestine like a frame. It consists of the appendix (also called vermiform appendix ‫)الزائدة الدودية‬, the caecum, the ascending colon, the transverse colon, the descending colon, the sigmoid colon, and the rectum. It has a length of approximately 1.5 meter and a diamater of 7.5cm. Water, vitamins and salts are absorbed in the large intestine before defecation. No chemical digestion occurs there but only mechanical. 13  AlMustafa University - School of Pharmacy - First year Human Biology lecture no. 7 – by Dr. Ali Yousif Al-Taei First Year - Biology lecture 7 – Pharmacy School – Dr. Ali Yousif The caecum is the first portion of the large intestine and it is described as an expanded pouch that receives material from the ileum portion of the small intestine and starts to compress food products into faecal material. Undigested food content then travels along the colon. Food content passes through the ascending colon, the transverse colon in a horizontal extension, then the descending colon on the left side, before reaching the sigmoid colon. The rectum is the final 15 cm segment of the large intestine. It expands to hold faecal material before it passes through the anorectal canal (also called anal canal) to the anus ‫الفتحة الشرجية‬. 14  AlMustafa University - School of Pharmacy - First year Human Biology lecture no. 7 – by Dr. Ali Yousif Al-Taei First Year - Biology lecture 7 – Pharmacy School – Dr. Ali Yousif B- Components of the accessory organs: 1- Teeth In most of adult human, there is 32 permanent teeth. While children have 20 primary or deciduous teeth ‫ اسنان لبنية‬by the age of 2-3 years. Note: deciduous teeth are also called milk teeth. Type of teeth: 8 Incisors – for cutting ‫قواطع‬ 4 Canines – for tearing ‫انياب‬ 8 Pre-molars & 12 molars – for grinding ‫طواحن‬ 15  AlMustafa University - School of Pharmacy - First year Human Biology lecture no. 7 – by Dr. Ali Yousif Al-Taei First Year - Biology lecture 7 – Pharmacy School – Dr. Ali Yousif ‫لالطالع‬ 2- Tongue A fleshy muscular structure attached at the hyoid bone and the lingual frenulum at the base of the mouth. Tongue is the organ in the mouth that is responsible for the taste sense ‫حاسة‬ ‫الذوق‬. It manipulates food for mastication ‫ مضغ‬and swallowing. ‫لالطالع‬ 16  AlMustafa University - School of Pharmacy - First year Human Biology lecture no. 7 – by Dr. Ali Yousif Al-Taei First Year - Biology lecture 7 – Pharmacy School – Dr. Ali Yousif 3- Salivary glands Are exocrine glands that are present in the oral cavity to produce saliva and mucin. Salivary glands are of three types and found in pairs: the parotid glands ‫( الغدد النكفية‬located behind each ear), the submandibular glands (secrete almost 70% of the total saliva), and the sublingual glands (the smallest salivary glands). 4- Liver Liver is the largest glandular organ in the body that is responsible for the biochemical synthesis of large proteins; hormones; and bile ‫ الصفراء‬, carbohydrate metabolism, conversion and storage of nutrients such as glucose and glycogen necessary for digestion and growth. It is located on the right side of the body under the diaphragm. It is connected to the gall bladder via the common hepatic duct. 17  AlMustafa University - School of Pharmacy - First year Human Biology lecture no. 7 – by Dr. Ali Yousif Al-Taei First Year - Biology lecture 7 – Pharmacy School – Dr. Ali Yousif 5- Gallbladder ‫المرارة او كيس الصفراء‬ It is a sac found below the liver. It stores bile produced from the liver to expel it into the duodenum upon need. The bile is a fluid-like material that helps break down fats. Gallbladder secrets the bile into the duodenum throughout the common bile duct. 6- Pancreas The pancreas is a pinkish-grey organ of the digestive system and endocrine system. It is located across the back of abdomen behind the stomach. Ther pancreas secretes enzymes and hormones (mainly insulin) to help break down mainly carbohydrates and to a lower extent proteins and fats. It consists of three portions: head, body, and tail. 18  AlMustafa University - School of Pharmacy - First year Human Biology lecture no. 7 – by Dr. Ali Yousif Al-Taei First Year - Biology lecture 7 – Pharmacy School – Dr. Ali Yousif 19