1 The Anatomy of the Digestive System!!!! Our mouth tears and grinds our food into small pieces- “mechanical digestion” Salivary glands release “saliva” and a digestive enzyme called “amylase” Our tongue pushes the pulpy mass to the back of our throat and we swallow! The food goes into our esophagus leading to out stomach Our stomach squeezes, sloshes and mixes the food- adds 2 important chemicals- HCL and pepsin

2 These chemicals change food into a thick liquid called “chyme” Chyme leaves our stomach and goes into the small intestine. Chemicals break complex sugars into simple sugars, proteins into amino acids and emulsify fats Bile is produced by the liver & stored in the gallbladder Our pancreas is a gland that adds more chemicals ; proteins that turn into amino acids enter our circulatory system where they are transported to the liver for storage The last step is called “absorption”

3 It occurs when nutrients pass through the wall of the small intestine and enter the circulatory system Only wastes remain—they enter the large intestine where water is removed from the wastes and returned to the body This is called “reabsorption” After this, wastes collect in the last 4- 6 inches of the large intestine This is called the rectum –defecation occurs when wastes are removed!!!

4 Very little was known about digestion until 1833, when a remarkable combination of circumstances enabled Dr. William Beaumont, an army doctor, to watch food being digested inside a human stomach. 11 years earlier Alexis St Martin, a fur trapper, had been accidentally shot at close range. Dr Beaumont saved St Martins life, but the wound left a permanent hole in St Martins stomach. From mucous tissue Dr. Beaumont fashioned a covering for the hole, but he arranged it so that it could be opened and closed. Did you know?

5 He paid St Martin to let him look through the hole at frequent intervals. Dr Beaumont made careful notes as he watched different kinds of foods being digested, and in 1833 his accurate descriptions of a human stomach digesting food were published in a book called A Window in the Stomach.

6 The Digestive System and Body Metabolism  The organs of the digestive system can be divided into two categories:  Digestion  Breakdown of ingested food  Absorption of nutrients into the blood  Metabolism  Production of cellular energy (ATP)  Constructive and degradative cellular activities

7 Organs of the Digestive System  Two main groups  Alimentary canal – continuous coiled hollow tube (also called the gastrointestinal (GI) tract) is about 30 feet!!!!!!!  Mouth, pharynx, esophagus, stomach, small intestine, and large intestine  Accessory digestive organs  Pancreas, liver, gallbladder, salivary glands, teeth

8 Organs of the Digestive System Figure 14.1

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10 Mouth (Oral Cavity) Anatomy  Lips (labia) – protect the anterior opening  Cheeks – form the lateral walls  Hard palate – forms the anterior roof  Soft palate – forms the posterior roof  Uvula – fleshy projection of the soft palate Figure 14.2a

11 Mouth (Oral Cavity) Anatomy  Vestibule – space between lips externally and teeth and gums internally  Oral cavity – area contained by the teeth  Tongue – attached at hyoid and styloid processes of the skull, and by the lingual frenulum Figure 14.2a

12 Processes of the Mouth  Mixes masticated food (chewing) with saliva  Initiation of swallowing by the tongue  Allowing for the sense of taste

13 Salivary Glands  Saliva  Helps to form a food bolus!!!  Contains salivary amylase which is only able to digest starch – the 1 st nutrient to be chemically digested!!!!  Dissolves chemicals so they can be tasted!!!!!

14 Teeth  The role is to masticate (chew) food  Humans have two sets of teeth  Deciduous (baby or milk) teeth  20 teeth are fully formed by age two  Permanent teeth  Replace deciduous teeth beginning between the ages of 6 to 12  A full set is 32 teeth, but some people do not have wisdom teeth

15 Classification of Teeth Figure 14.9

16 Regions of a Tooth-What is gingivitis?  Crown – exposed part  Outer enamel  Dentin  Pulp cavity  Neck  Region in contact with the gum  Connects crown to root  Root  Periodontal membrane attached to the bone  Root canal carrying blood vessels and nerves Figure 14.10

17 Pharynx Anatomy  Nasopharynx – not part of the digestive system  Oropharynx – posterior to oral cavity  Laryngopharynx – continuous with esophagus Figure 14.2a

18 Pharynx Function  Serves as a passageway for air and food  Food is propelled to the esophagus by two muscle layers  Longitudinal inner layer  Circular outer layer  Food movement is by alternating contractions of the muscle layers (peristalsis)

19 Esophagus  Runs from pharynx to stomach through the diaphragm  Conducts food by peristalsis (slow rhythmic squeezing)  Passageway for food only (respiratory system branches off after the pharynx)  Has NO digestive function!!!!!

20 Layers of Alimentary Canal Organs Figure 14.3

21 Stomach Anatomy- 10” long; when full it can hold 1 gal or 4 liters of food!!!  Located on the left side of the abdominal cavity, almost hidden by the liver  Food enters at the cardioesophageal sphincter from the esophagus  Hydrochloric acid (HCL) activates pepsinogen to pepsin

22 Stomach  Regions of the stomach  Cardiac region – near the heart  Fundus- expanded part  Body- midportion  Phylorus – funnel-shaped terminal end  Food empties into the small intestine at the pyloric sphincter- the “gatekeeper” to the small intestine

23 Stomach Anatomy  Rugae – internal folds of the mucosa  External regions  Lesser curvature  Greater curvature  Layers of peritoneum attached to the stomach  Lesser omentum – attaches the liver to the lesser curvature  Greater omentum – attaches the greater curvature to the posterior body wall -Covers abdominal organs like a lacy apron!!!! -Contains fat to insulate, cushion, and protect abdominal organs

24 Stomach Functions  Acts as a storage tank for food  Site of food breakdown  Most digestive activity occurs in the pyloric region  Chemical breakdown of protein begins  Delivers chyme (processed food- similar to heavy cream!!!) to the small intestine

25 Stomach Anatomy Figure 14.4a

26 Small Intestine- is it “small” because of length in comparison to the large intestine??????  The body’s major digestive organ  Absorption of nutrients!!!!  Muscular tube extending from the pyloric sphincter to the ileocecal valve  Suspended from the posterior abdominal wall by the mesentery

27 Subdivisions of the Small Intestine  Duodenum  Attached to the stomach  Curves around the head of the pancreas  Jejunum  Attaches anteriorly to the duodenum  Ileum  Extends from jejunum to large intestine OH of small intestine #219

28 Chemical Digestion in the Small Intestine Figure 14.6

29 Villi of the Small Intestine  Fingerlike structures formed by the mucosa  Give the small intestine more surface area Figure 14.7a

30 Large Intestine Figure 14.8

31 Functions of the Large Intestine  Absorption of Vitamins B and K + water  Eliminates indigestible food from the body as feces  Does not participate in digestion of food  Goblet cells produce mucus to act as a lubricant

32 Structures of the Large Intestine  Cecum – saclike first part of the large intestine  Appendix  Accumulation of lymphatic tissue that sometimes becomes inflamed (appendicitis)  Hangs from the cecum

33 Structures of the Large Intestine  Colon  Ascending  Transverse  Descending  S-shaped sigmoidal  Rectum  Anus – external body opening

34 Pancreas  The pancreatic duct connects the pancreas at the duodenum  It quickly and efficiently neutralizes acidity to prevent damage to the mucosa lining!!!!!  Alkaline fluid is introduced with enzymes neutralizes acidic chyme  Endocrine products of pancreas-regulate blood sugar level in blood  Insulin-released when rising( eating 4 donuts)  Glucagons- released when low (skip a meal)

35 Liver  Largest gland in the body  Located on the right side of the body under the diaphragm  Consists of four lobes suspended from the diaphragm and abdominal wall by the falciform ligament  Connected to the gall bladder via the common hepatic duct  Detoxifies drugs and alcohol

36 Bile  Produced by cells in the liver-  buildup leads to pigments circulating in the body;tissues to turn yellow; “jaundice”.  Composition  Bile  salts,Cholesterol,Phospholipids,Electrolyte ***Bile is introduced into the duodenum for absorption of fats and fat soluble vitamins in the small intestine

37 Gall Bladder  Sac found in hollow fossa of liver  Stores bile from the liver by way of the cystic duct  Gallstones can cause blockages

38 Processes of the Digestive System  Ingestion – getting food into the mouth  Propulsion – moving foods from one region of the digestive system to another  Peristalsis – alternating waves of contraction  “Segmentation” – moving materials back and forth to aid in mixing

39 Processes of the Digestive System  Mechanical digestion  Mixing of food in the mouth by the tongue  Churning of food in the stomach  Segmentation in the small intestine  Chemical Digestion  Enzymes break down large food molecules into their building blocks  Each major food group uses different enzymes  Carbohydrates are broken to simple sugars (sucrose,lactose,maltose,starch)  Proteins are broken to amino acids  Fats are broken to fatty acids and alcohols

40 Processes of the Digestive System  Absorption  End products of digestion are absorbed in the blood or lymph  Defecation  Elimination of indigestible substances as feces

41 Processes of the Digestive System Figure 14.11

42 Deglutition (Swallowing)  Buccal phase  Voluntary-  Occurs in the mouth  The bolus is forced into the pharynx by the tongue  Pharyngeal-esophageal phase- larynx is NOT involved!  Involuntary transport of the bolus  All passageways except to the stomach are blocked  Tongue blocks off the mouth  Soft palate (uvula) blocks the nasopharynx  Epiglottis blocks the larynx  Peristalsis moves the bolus toward the stomach  The cardioesophageal sphincter is opened when food presses against it  Swallowing and peristalsis both assist in propulsion from 1 digestive organ to another!!!!!

43 Deglutition (Swallowing) Figure 14.13

44 Metabolism  Chemical reactions necessary to maintain life  Catabolism – substances are broken down to simpler substances  Anabolism – larger molecules are built from smaller ones  Energy is released during catabolism

45 Metabolic Functions of the Liver Figure 14.20

46 Metabolic Rate and Body Heat Production  Basic metabolic rate (BMR) – amount of heat produced by the body per unit of time at rest  Factors that influence BMR  Surface area – small body usually has higher BMR  Gender – males tend to have higher BMR  Age – children and adolescents have a higher BMR