Topic 20: The Digestive System

The human digestive organisation is formed of the digestive tract, a serial of tube-like organs through which the nutrient passes, every bit good every bit some accessory organs through which nutrient does non pass.  The digestive tract begins at the mouth too continues with the esophagus, stomach, minor intestine, large intestine, rectum too anus.  Accessory organs include the tongue, teeth, salivary glands, gallbladder, liver too pancreas.

MOUTH

Food inward the oral cavity is chewed yesteryear teeth, moistened yesteryear saliva too the formed into a bolus yesteryear the tongue.

Teeth are really of import for chewing the food, which increases the surface expanse on which the digestive enzymes tin act.

Teeth are flora embedding inward the jaw bones (maxilla too manidible) too the roots are held inward house yesteryear a layer of cementum.  The jaw bones are covered yesteryear a soft tissue called gums.  Above the gumline is the crown of the tooth.

Dental Health

Cavities (fogszuvasodás) are holes inward the enamel roofing the crown of the tooth.  The forcefulness of the enamel is subject on the torso having appropriate amounts of fluoride too also on genetics.  The pH of the saliva varies from somebody to somebody too if a person's saliva is below 5.5, that speeds upwards the demineralization of the enamel.  In general, cavity formation occurs when sugars inward the oral cavity (from the nutrient that nosotros eat) are consumed yesteryear bacteria that are also flora inward the oral cavity (usually on the teeth too gums).  The bacteria arrive at acids inward the procedure of digesting the carbohydrate too these acids laid out degrading the enamel surface of the tooth. This creates minor indentations on the enamel surface.  As this procedure continues, the indentations go holes too if non filled, the hole tin extend into the soft dentine inner layer of the tooth too hence into the pulp, causing pain, since the pulp contains nervus endings.  

Brushing teeth rubs bacteria too nutrient particles off the surface of teeth too from spaces betwixt the teeth.  Flossing moves bacteria too nutrient from the really narrow spaces betwixt teeth.  Rinsing the oral cavity with H2O (or mouthwash) later on brushing too flossing removes the bacteria from the mouth.  Regular dental check-ups are useful every bit the dentist tin select handgrip of cavities earlier they take hold go really large or painful too it is much easier to insert a minor filling.  Likewise, many dentists supply fluoride treatments, which help to remineralize too strengthen the enamel.

Dentition

Names of the dissimilar types of teeth

Humans take hold dissimilar kinds of teeth, which serve slightly dissimilar functions, although human teeth, inward general, exhibit less variation inward size than what is seen inward many other mammals.

Incisors (metszőfog) are designed for biting, canines (szemfog) are designed for violent too premolars (kisörlő) too molars (nagyörlő) are designed for chewing/mashing the food.  The 3rd prepare of molars are often referred to every bit wisdom teeth.  In modern humans, non everyone grows a 3rd prepare too many people who do honour that their jaw is also minor to accomodate them, hence they are oftentimes removed yesteryear the dentist.

Humans take hold ii sets of teeth inward their lifetime: babe or milk teeth too adult or permanent teeth.

The tongue, along with the difficult too soft palates on the roof of the mouth, play an of import role inward forming the chewed nutrient into a ball (bolus) for swallowing.  The natural language also makes eating to a greater extent than enjoyable since its surface is covered with papillae, which incorporate the tastebuds.  There are v types of tastebuds - sweet, sour, bitter, salty too umami.  When swallowing the uvula (nyelvcsap) prevents nutrient from moving upwards the nasal passages.

Saliva is produced yesteryear salivary glands that are flora lining the inner walls of the oral cavity too yesteryear multicellular glands flora nether the natural language (sublingual), nether the tonsils (submandibular) too upwards nigh the ears (parotid).

Salivary glands

Saliva contains salivary amylase, an enzyme that behavior out the firstly steps of chemic digestion correct inward the mouth.  It digests starches to glucose.


ESOPHAGUS

The esophagus is a long muscular underground attaching the oral cavity to the esophagus.  Movement downwardly the underground occurs with a special ringlike contraction called peristalsis.

At the bottom of the esophagus is a sphincter (ring-like muscle) that closes off the tum from the esophagus.  When the sphincter does non closed properly, the somebody tin sense reflux (also called heartburn), when the contents of the tum displace upwards into the esophagus.

STOMACH

The tum is a muscular sac inward which the nutrient is mixed yesteryear peristalsis with gastric juice, to create a sparse watery liquid called chyme.  Gastric juice contains water, mucus, HCl too pepsin.  Pepsin is an enyme that digests proteins.  It functions best at a depression pH, hence HCl is needed to help maintain a pH of 2 inward the stomach, to ensure that pepsin does its job.  Mucus (nyálka) is a necessary element of gastric juice, every bit the depression pH is harmful to the cells that draw the tum too mucus protects them.  Chyme is prevented from moving on to the minor intestine yesteryear the pyloric sphincter (ring-like muscle) too nutrient typically spends 2-4 hours inward the stomach.

The stomach

SMALL INTESTINE

The minor intestine is a long underground (about 6m) with a really minor diameter (2.5cm).  It plays a role inward both chemical digestion too nutrient absorption.  It is formed of three parts, the duodenum (patkóbél), the jejunum (éhbél) too the ileum (csípőbél) , too is closely associated with the accessory organs of the digestive system.

 Accessory Organs of the Digestive System

1.  Liver (máj):  It is a large, reddish-brown organ that produces bile (epe).  It also plays other roles exterior of the digestive system: iron, vitamin H5N1 too D too glycogen storage, breaks downwardly toxins, stores toxins that can’t live broken down)  

Bile – Made yesteryear liver, stored inward gallbladder.  It contains mineral salts which neutralize the acidity of the chyme every bit it enters the minor intestine from the highly acidic stomach.  It also contains bile acids which emulsify lipids.  This agency they movement the lipids to split upwards into really minor lipid globules, which provides to a greater extent than surface expanse for enzymes to react with.  This is a shape of mechanical digestion.  Bile is greenish inward colour,which is because it contains bile pigments which are the products of haemoglobin break-down (another business office of the liver)

Bile travels from the liver to the gallbladder through the hepatic ducts too hence from the gallbladder to the duodenum (small intestine) via the mutual bile duct.

2.  Gallbladder (epeholyag):  The gallbladder's role is to shop the bile until it is needed  in the minor intestine.  

3.  Pancreas (hasnyálmirigy):  The pancreas makes pancreatic juice which contains digestive enzymes, but also plays a  role exterior the digestive system, yesteryear producing  insulin too glucagon (hormones) which regulate blood sugar.

Pancreatic juice - It contains mineral salts to help maintain the pH of the minor intestine betwixt 7.5 too 8.  It also contains enzymes, including pancreatic amylase which digests starches, trypsin which digests proteins, lipases which digest lipids, too nucleases which digest nucleic acids. 

The minor intestine:  The duodenum is the initial horseshoe-shaped section, into which the bile too pancreatic juice enters via the mutual bile duct.  The jejunum is the central, highly folded portion too the ileum is the lastly segment that leads into the large intestine.

The minor intestine also produces some enymes which are flora inward the intestinal juice, which is secreted yesteryear glands on the wall of the minor intestine.  It contains H20, ions, mucus too the enzymes maltase (which digests the carbohydrate maltose), sucrase (which digests sucrose), lactase (which digests lactose), nucleotidase (which digests nucleotides) and   peptidases (which digest peptides).

Nutrient absorption is a really of import business office of the jejunum too the ileum.  In particular, this is where glucose, ions, amino acids, obese acids too glycerol, nucleic acids too vitamins are absorbed.  The construction of the within of the minor intestine is designed to ensure that at that topographic point is lots of surface expanse for absorption to take hold place. The walls of the minor intestine are covered with villi, which are finger-like projections of the intestinal wall.  Each villus is made upwards of hundreds of specialized epithelial cells which are covered with microvilli.   Within each villus is a network of capillaries to behavior the absorbed materials throughout the body.  Villi too microvilli increment the surface expanse of the minor intestine tremendously, hence that it is essentially the same every bit the surface expanse of a lawn tennis court!!  Chyme usually spends three to vi hours inward the minor intestines. 

Wall of the minor intestine

LARGE INTESTINE

The primary role of the large intestine is to absorb water, salts too minerals from the undigested chyme.  

The large intestine

The minor intestine joins with the large intestine correct nigh the caecum (vakbél), which is considered to live a rudimentary organ in humans.  It plays a role inward herbivores (where it is larger than inward humans too houses special microbes) inward cellulose digestion).  

The appendix (féregnyulvány) is a really minor extention of the caecum, which plays a role inward immune function.  If the appendix becomes infected, hence the somebody has appendicitis.  

The colon has four sections, based on their seat (ascending, transverse, descending too sigmoid).  Absorption of water, salts too minerals occurs inward the colon.  

It is also the abode to really of import bacterial flora.  Somewhere betwixt 300 too M dissimilar species of bacteria alive inward our guts, but fungi too protozoa are also flora there.  The human relationship betwixt humans too their gut bateria is mutualistic.  Humans supply the bacteria with nutrient too a rubber environs too the microorganisms behavior out useful functions, such every bit fermenting unused unloose energy substrates, preparation the immune system, preventing growth of harmful, pathogenic bacteria, regulating the evolution of the gut, producing vitamin B7 and vitamin K too producing hormones that immediately obese storage.  The numbers too types of microbes that are flora inward the gut vary with age, diet, illness, exposure to antibiotics, etc.  In for certain conditions, some species are idea to live capable of causing or preventing disease, affecting weight loss or gain, too fifty-fifty affecting the host's take chances of cancer.
After nigh 18-36 hours inward the large intestine, H2O has been fully reabsorbed too the remaining textile (a mixture of undigested chyme too microflora) is stored every bit faeces inward the rectum, until they are released through the anus.
Insufficient reabsorption of H2O causes diarrhea, spell also much reabsorption results inward constipation.  Diarrhea is oftentimes the outcome of an infection and, if it is non also serious, handling includes staying good hydrated too eating nutrient depression inward fibre.  Diarrhea is a mutual ailment inward developing countries where H2O is consumed without appropriate handling too people are exposed to many pathogens.  It is also a really mutual movement of expiry (due to dehydration) with children inward these countries.  Constipation is a to a greater extent than mutual ailment inward Western societies, where a depression fibre diet too piddling physical activity are mutual causes.  Increasing dietary fibre, H2O intake too doing physical practise tin help to alleviate the problem.

Conditions too Illnesses

Gastroesophageal reflux affliction (GERD)
- symptoms: persistent heartburn, bad breath, tooth erosion, nausea, hurting inward breast or upper abdomen, problem swallowing breathing

-treatment:  avoiding foods that trigger symptoms (eg. spicy food, carbonated drinks, etc), non eating large meals, non lying downwardly presently later on eating, over-the-counter antacids

Gallstones

-hard deposits that shape inward the gallbladder if the bile contains also much cholesterol or bilirubin, or non plenty bile salts.

-symptoms:  sharp hurting inward upper correct abdomen

-treatment:  medications to dissolve stones, surgery

Cirrhosis of the liver

-liver slow deteriorates too salubrious tissue is replaced yesteryear scar tissue.  Liver loses its function. It tin live caused yesteryear hepatitis C infection, obesity, diabetes or overconsumption of alcohol.

-symptoms:  jaundice (yellowing of skin), fatigue, weakness, loss of appetite, itching 

-treatment: lifestyle changes, liver replacement surgery

Celiac Disease

- a serious gluten allergy (gluten is a poly peptide flora inward wheat, barley, etc), which results inward the immune organisation destroying the villi of the minor intestine

- symptoms:  abdominal pain, bloating, diarrhea, constipation, weight loss, anemia, fatigue, os loss, depression, seizures

- treatment:  removing gluten from the diet

Crohn's Disease

- an autoimmune affliction that causes inflammation of the bowel at the ileum too commencement of the large intestine, obese wrapping around the intestine too a "cobblestoning" of the lining of the bowel wall.

- symptoms:  abdominal pain, diarrhea, rectal bleeding, weight loss, fever

- treatment:  depends on symptoms, includes diet, topical hurting relievers, immunosuppressants too surgery

Ulcerative colitis

- similar to Crohn's for symptoms too treatment, but inflammation is flora throughout the colon too non inward the ileum.  The lining of the colon wall is ulcerated.

Irritable bowel syndrome

- symptoms vary:  diarrhea, constipation, bloating

- causes:  irregular peristalsis, stress, anxiety, depression, binge eating, smoking

- treatment:  diet - avoiding trigger foods, increasing fibre too probiotics

Hemorroids

- inflammation of blood vessels at the halt of the digestive tract caused yesteryear chronic constipation, straining, lack of fibre inward diet

- symptoms:  pain, itchiness

- treatment: high-fibre diet, to a greater extent than H2O too exercise, creams too suppositories