The Human BodyStructure & Function of Major Systems of the Human Body Zarin Rahman, AP Bio 2013
The Digestive System Just Guts!
Function • Turns food into energy needed to survive and packages residue for waste disposal. • Mechanical and chemical breakdown of food. • Food enters mouth (mastication) › travels down esophagus (deglutition) › enters the stomach and intestine (digestion) › waste is eliminated (defecation).
Major and Accessory Organs • Major organs of digestion: • Mouth • Esophagus • Stomach • Small intestine • Large intestine • Rectum • Anus • Accessory organs of digestion: • Gallbladder, pancreas, and liver.
Part One: Mastication • When food enters the mouth, digestion starts by mastication, a form of mechanical digestion, and the contact of saliva. • Saliva, secreted by salivary glands, contains salivary amylase, an enzyme that digests starch in food. • Food forms into bolus.
Part Two: Deglutition • Bolus is pushed into esophagus through the pharynx. • Using smooth muscle contractions known as peristalsis, the esophagus delivers food to stomach. • At junction of the esophagus/stomach,ring-like muscle (lower esophagealsphincter) closes passage between.As food approaches, the sphincter relaxes and allowsthe food to pass through to the stomach.
Part Three: Digestion • Stomach is a small, 'J'-shaped pouch with walls made of thick, distensible muscles. • Food enters the stomach through the cardiac orifice, further broken apart and thoroughly mixed with gastric acid, pepsin and other digestive enzymes to break down proteins. • Enzymes require optimum pH tocreate acidic conditions in whichthey work best.
Part Three: Digestion • Pepsin in the stomach denatures proteins, reducing polypeptide bonds and disrupting salt bridges, which causes a loss of 2˚, 3˚, or 4˚ protein structure. • Parietal cells of stomach also secrete a glycoprotein called intrinsic factor, which enables the absorption of vitamin B-12. • Mucus neck cells of stomach secrete mucus, which along with gastric juice lubricates and protects mucosal epithelium from excoriation by highly concentrated hydrochloric acid.
Part Three: Digestion • Small molecules (i.e. alcohol) are absorbed, passing through membrane of stomach and entering circulatory system directly. • Food in the stomach is in semi-liquid form, which upon completion is known as chyme. (approx. 2-4 hours after mastication & deglutition)
Part Three: Digestion • Peristaltic contractions begin, help break down food and move it onward. Chyme reaches the opening to the duodenum (pylorus) and retropulsion exerts additional force and further grinds down food into smaller particles. • Gastric emptying occurs, releasing of food from stomach into the duodenum. • After being processed in the stomach, food is passed to small intestine via pyloric sphincter. • Majority of digestion and absorption occurs after the milkychyme enters the duodenum.
Part Three: Digestion • Chyme mixed with 3 other liquids: • Bile: emulsifies fats to allow absorption, neutralizes chyme, used to excrete waste products such as bilin and bile acids. Bile is produced by the liver and then stored in the gallbladder where it will be released to the small intestine via the bile duct.
Part Three: Digestion • Pancreatic juice made by the pancreas, which secretes enzymes such as pancreatic amylase, pancreatic lipase, and trypsinogen (inactive form of protease). Helps digest proteins, carbohydrates, and fats.
Part Three: Digestion • Intestinal juice secreted by the intestinal glands in the small intestine. It contains enzymes such as enteropeptidase, erepsin (which further digests polypeptides into amino acids, completing protein digestion), trypsin, chymotrypsin, maltase, lactase and sucrase (all three of which process only sugars). • Small, finger-like structures (villi) and their epithelial cells covered with numerous microvilli improve absorption of nutrients by increasing surface area of intestine, enhancing speed of absorption. Blood containing absorbed nutrients is carried from small intestine via the hepatic portal vein to the liver for filtering, removal of toxins, and nutrient processing.
Part Three: Digestion • Whatever material is left goes into the large intestine. • Function: storage and fermentation of indigestible matter. • Four parts: ascending colon, descending colon, transverse colon, and sigmoid colon.
Part Three: Digestion • Less vigorous in absorption activity. • Digestion is retained to allow fermentation due to the action of bacteria, which breaks down some of the substances that remain after processing in the small intestine; some of the breakdown products are absorbed. In humans, these include most complex saccharides. • Large intestine absorbs water from the chyme and stores feces.
Part Four: Defecation • Waste product is stored in the rectum for a certain period and then waste is eliminated from the body through contraction and relaxation through the anus. • The exit of this waste material is regulated by the anal sphincter.
A Closer Look: Breakdown & Absorption • Proteins • Occurs in the stomach and duodenum in which 3 main enzymes, pepsin secreted by the stomach and trypsin and chymotrypsin secreted by the pancreas, break down food proteins into polypeptides that are then broken down by various exopeptidases and dipeptidases into amino acids.
A Closer Look: Breakdown & Absorption • Fats • Can begin in the mouth where lingual lipase breaks down some short chain lipids into diglycerides. Presence of fat in small intestine produces hormones that stimulate the release of pancreatic lipase from the pancreas and bile from the liver for breakdown of fats into fatty acids. Complete digestion of one molecule of fat (a triglyceride) results in 3 fatty acid molecules and one glycerol molecule.
A Closer Look: Breakdown & Absorption • Carbohydrates • Bonds between glucose molecules broken by salivary and pancreatic amylase, resulting in smaller chains of glucose. Results in simple sugars glucose and maltose that can be absorbed by the small intestine. • Lactase breaks down the disaccharide lactose to its component parts, glucose and galactose. Glucose and galactose can be absorbed by the small intestine. • Sucrase breaks down the disaccharide sucrose. Sucrose digestion yields the sugars fructose and glucose which are readily absorbed by the small intestine.
A Closer Look: Breakdown & Absorption • DNA & RNA • DNA and RNA are broken down into mononucleotides by the nucleases deoxyribonuclease and ribonuclease (DNase and RNase) from the pancreas.
Chemical vs. Mechanical Digestion CHEMICAL MECHANICAL • Catabolism • Glandular structures, dispersed throughout the body, are involved in breaking food into simple molecules that can be absorbed. • Use of enzymes. • Mastication • Food is crushed and liquefied by the teeth, tongue Break down of food into usable energy molecules. • Peristalsis • Waves of involuntary muscle contraction of the stomach and small intestine.
Disorders of the Digestive System • Celiac Disease • an autoimmune disorder of the small intestine that occurs in genetically predisposed people of all ages from middle infancy onward • caused by a reaction to gliadin, a prolamin (gluten protein) found in wheat, and similar proteins found in the crops of the tribe Triticeae (which includes other common grains such as barley and rye)
Disorders of the Digestive System • Celiac Disease: Signs & Symptoms • Pale, loose and greasy stool (steatorrhoea). • Weight loss or failure to gain weight (in young children). • Intermittent diarrhea • Abdominal pain • Bloating • Irritability or depression, anemia, stomach upset, joint pain, muscle cramps, skin rash, south sores, dental and bone disorders (such as osteoporosis), tingling in the legs and feet (neuropathy) may also occur.
Disorders of the Digestive System • Celiac Disease : Prevalence • Affects between 1 in 1,750 in the world, and 1 in 105 people in the United States. • Almost all people with celiac disease have either the variant HLA-DQ2 allele or (less commonly) the HLA-DQ8 allele. However, about 20–30% of people without celiac disease have also inherited either of these alleles. This suggests additional factors are needed for celiac disease to develop.
Disorders of the Digestive System • Celiac Disease: Treatment • Diet- To manage the disease and prevent complications, it's crucial to avoid all foods that contain gluten, including: barley, bulgur, durum, farina, graham flour, rye, semolina, spelt (a form of wheat), triticale, wheat • Supplements- Take vitamin and mineral supplements recommended by doctors or dietitian to help correct deficiencies: Calcium, folate, iron, vitamin B-12, vitamin, vitamin K
Disorders of the Digestive System • Crohn’s Disease • Type of inflammatory bowel disease that may affect any part of the gastrointestinal tract from mouth to anus, causing a wide variety of symptoms. • Causes inflammationof the lining of your digestive tract.
Disorders of the Digestive System • Crohn’s Disease: Signs & Symptoms • Diarrhea • Abdominal pain and cramping • Blood in stool • Ulcers • Reduced appetite and weight loss • Other symptoms include: fever, fatigue, arthritis, eye inflammation, mouth sores, skin disorders, inflammation of the liver or bile ducts, delayed growth or sexual development (in children)
Disorders of the Digestive System • Crohn’s Disease: Prevalence • Affects between 400,000 and 600,000 people in North America. • Prevalence estimates for Northern Europe have ranged from 27–48 per 100,000. • Crohn's disease tends to present initially in the teens and twenties, with another peak incidence in the fifties to seventies, although the disease can occur at any age.
Disorders of the Digestive System • Crohn’s Disease: Treatment • There is currently no cure for Crohn's disease, and there is no one treatment that works for everyone. • Treatment for Crohn's disease usually involves drug therapy or, in certain cases, surgery. • Anti-inflammatory drugs: Sulfasalazine, Mesalamine, Corticosteroids. • Immune system suppressors: Azathioprine, Mercaptopurine, Infliximab, Adalimumab, Certolizumabpegol, Methotrexate, Cyclosporine, Natalizumab. • Antibiotics: Metronidazole, Ciprofloxacin. • Other drugs: anti-diarrheals, laxatives, pain relievers, vitamin B-12 shots, supplements.
The Endocrine System Why was the endocrine student so upset?He failed a teste.
Function • System of glands, each of which secretes different types of hormones directly into the bloodstream to maintain homeostasis. • An information signal system like the nervous system. • Hormones regulate various human functions, including metabolism, growth and development, tissue function, sleep, and mood.
Homeostasis & the Endocrine System • What is homeostasis? • The human body’s ability to maintain balance or return systems to functioning within a normal range. Interactions within the body facilitate compensatory changes supportive of physical and psychological functioning. • The liver, the kidneys, and the brain (hypothalamus, the autonomic nervous system and the endocrine system) help maintain homeostasis.
Homeostasis & the Endocrine System • Role of endocrine system: • synthesizing and releasing hormones, chemical messengers. • major areas of control and integration include responses to stress and injury, growth and development, absorption of nutrients, energy metabolism, water and electrolyte balance, reproduction, birth, and lactation. • many endocrine glands are linked to neural control centers by homeostatic feedback mechanisms. The two types of feedback mechanisms are negative feedback and positive feedback. • most are negative feedback mechanisms
Negative Feedback Mechanisms • Negative feedback mechanisms act like a thermostat in the home. As the temperature rises (deviation from the idealnormal value), the thermostatdetects the change and triggersthe air-conditioning to turn on and cool the house. Once the temperature reaches its thermostat setting (ideal normal value), the air conditioning turns off.
Negative Feedback Mechanisms • Blood calcium level. • parathyroid glands secrete parathyroid hormone, which regulates the blood calcium • if calcium decreases, parathyroid glands sense the decrease and secrete more parathyroid hormone. Parathyroid hormone stimulates calcium release from bones and increases the calcium uptake into the bloodstream from the collecting tubules in the kidneys. • conversely, if blood calcium increases too much, the parathyroid glands reduce parathyroid hormone production. • both responses are examples of negative feedback because in both cases the effects are negative (opposite) to the stimulus.
Negative Feedback Mechanisms • Blood calcium level.
Insulin and Cell Signaling • Insulin is the major hormone controlling critical energy functions such as glucose and lipid metabolism. • insulin activates the insulin receptor tyrosine kinase (IR), which phosphorylates and recruits different substrate adaptors. • activated Akt induces glycogen synthesis, and cell survival. • insulin stimulates glucose uptake in muscle and adipocytes via translocation of GLUT4 vesicles to the plasma membrane.
Insulin and Cell Signaling • Complex insulin cell signalinginvolving allintermediates.
Insulin and Cell Signaling • Low glucose vs. Elevated glucose level and the action of insulin.
Type I Diabetes vs. Type II Diabetes TYPE I DIABETES TYPE II DIABETES Body can’t use its insulin. Body make no insulin. Can be due to genetic factors. Usually in children and teens. Also due to obesity. Feeling tired or ill, frequent urination, tiredness, unusual thirst, weight loss, blurred vision, frequent infections and slow wound healing, asymptomatic. Usually in adults and the elderly 5% -10% of total cases. 90%- 95%-of total cases.
Disorders of the Endocrine System • Acromegaly • syndrome that results when the anterior pituitary gland produces excess growth hormone (GH) after epiphyseal plate closure at puberty. • most commonly affects adults in middle age, and can result in severe disfigurement, complicating conditions, and premature death if unchecked. Because of its pathogenesis and slow progression, the disease is hard to diagnose in the early stages and is frequently missed for years until changes in external features, especially of the face, become noticeable. • acromegaly is often associated with gigantism.
Disorders of the Endocrine System • Acromegly: Signs and Symptoms • Enlarged hands and feet • Coarsened, enlarged facial features • Coarse, oily, thickened skin • Excessive sweating and body odor • Small outgrowths of skin tissue (skin tags) • Fatigue and muscle weakness • A deepened, husky voice due to enlarged vocal cords and sinuses • Severe snoring due to obstruction of the upper airway • Impaired vision • Headaches • Enlarged tongue • Pain and limited joint mobility • Menstrual cycle irregularities in women • Erectile dysfunction in men • Enlarged liver, heart, kidneys, spleen and other organs • Increased chest size (barrel chest)
Disorders of the Endocrine System • Acromegaly
Disorders of the Endocrine System • Acromegaly: Prevalence • approximately 4,676 cases per million population, and the incidence is 116.9 new cases per million per year.
Disorders of the Endocrine System • Acromegaly: Treatment • The goals of treatment are to reduce GH production to normal levels, to relieve the pressure that the growing pituitary tumor exerts on the surrounding brain areas, to preserve normal pituitary function, and to reverse or ameliorate the symptoms of acromegaly. Currently, treatment options include surgical removal of the tumor, drug therapy, and radiation therapy of the pituitary. André René Roussimoff, aka Andre the Giant, famous actor and wrestler, suffered from acromegaly. He was 7 feet 4 inches and 520 pounds when he died from heart compliations (due to acromegaly) at age 46.
Disorders of the Endocrine System • Acromegaly: Treatment • Drugs • Somatostatin analogues • The primary current medical treatment of acromegaly is to use somatostatin analogues – octreotide (Sandostatin) or lanreotide (Somatuline). These somatostatin analogues are synthetic forms of a brain hormone, somatostatin, which stops GH production. • Dopamine agonists • For those unresponsive to somatostatin analogues, treatment using one of the dopamine agonists, Bromocriptine (Parlodel) or Cabergoline.
Disorders of the Endocrine System • Acromegaly: Treatment • Surgery • Surgery is a rapid and effective treatment, of which there are two alternative methods. The first method, a procedure known as EndonasalTransphenoidal surgery, involves the surgeon reaching the pituitary through an incision in the nasal cavity wall. The wall is reached by passing through the nostrils with microsurgical instruments. The second method is Transsphenoidal surgery during which an incision is made into the gum beneath the upper lip.
Disorders of the Endocrine System • Acromegaly: Treatment • Radiation Therapy • Radiation therapy has been used both as a primary treatment and combined with surgery or drugs. It is usually reserved for patients who have tumor remaining after surgery. These patients often also receive medication to lower GH levels. his treatment lowers GH levels by about 50 percent over 2 to 5 years.