Human Anatomy sec.4 PDF

Human anatomy sec.4 D\ Menna Maher  Digestion: How the body breaks down food During digestion, the body breaks food down into smaller parts. This enables them to enter cells, providing energy and other benefits.  Around 30 feet (9 meters) long in...

Human anatomy sec.4 D\ Menna Maher  Digestion: How the body breaks down food During digestion, the body breaks food down into smaller parts. This enables them to enter cells, providing energy and other benefits.  Around 30 feet (9 meters) long in adults. - It consists of the following: the mouth, or oral cavity The human gastrointestinal the esophagus tract (GIT) = The alimentary the stomach canal the small intestine the large intestine, or colon the rectum  the teeth the tongue In addition, the following organs support digestion the salivary glands , for example, - by chewing the liver - adding enzymes and other secretions that enable the body to absorb nutrients: the pancreas the gallbladder Some terms to describe these functions include: Ingestion, which includes chewing and swallowing The secretion of substances that enable food and nutrients to move through the body effectively Digestion, the breakdown of food, for example, through chewing and secretions Defecation and urination , the removal of waste products through the rectum and the bladder  The mouth Once the food is inside of the mouth: saliva moistens it. the teeth and tongue break it down mechanically. an enzyme in the saliva, salivary amylase, breaks down starch into smaller molecules. Chewing and amylase digestion will convert the food into a small, round blob, or bolus.  The esophagus After swallowing, the bolus enters the esophagus, where gravity and muscle contractions help move it down to the stomach through a process called peristalsis. Peristalsis is the slow contraction of smooth muscles along and around the digestive system. As the bolus moves through the esophagus, these contractions push it toward the stomach. Lower esophageal sphincter When food reaches the end of your esophagus, a ringlike muscle—called the lower esophageal sphincter —relaxes and lets food pass into your stomach. This sphincter usually stays closed to keep what’s in your stomach from flowing back into your esophagus.  The stomach * In the stomach, the following processes occur: The stomach stores the food temporarily. Cells in the stomach secrete gastric juices (ex: hydrochloric acid), which maintains the pH of the stomach between 1.5–2.0. These processes turn the food into a thick paste (= chyme). *Hydrochloric acid is essential for: destroying microorganisms, such as bacteria breaking down proteins and plant fibers activating pepsin, an enzyme that helps digest proteins The acid, however, can harm the stomach lining , so some cells produce mucus to protect the lining from damage.  The small intestine The small intestine is around 20 ft (6 m) long and absorbs around 90% of the nutrients from food into the bloodstream. There are three sections: The duodenum: This receives chyme from the stomach The jejunum: Most of the chemical digestion and absorption occur here. The ileum: through which food passes to the large intestine.  The large intestine The large intestine is around 6 ft (2 m) long and consists of the: ascending colon transverse colon descending colon sigmoid colon  The large intestine Any unabsorbed food and nutrients now pass to the large intestine, or colon. The material is now feces. From the large intestine, the body absorbs water and electrolytes. Next, peristalsis moves the feces toward the rectum. The rectum As the digested food moves into the rectum, nerves in the wall of the rectum known as stretch receptors detect when the chamber is full and stimulate the desire to defecate.  https://youtu.be/9v6VBKH9px0?si=DhusjBU4b-tYify2