1. The Digestive System & Body Metabolism Chapter 14 Part C

2. Accessory Digestive Organs
Teeth
Salivary glands
Pancreas
Liver
Gallbladder

3. Teeth The role is to masticate (chew) food
Humans have two sets of teeth
Deciduous (baby or milk) teeth
Come in at 6 months
20 teeth are fully formed by age two
Permanent Teeth
Replace deciduous teeth beginning between the ages of 6 to 12
Full set by age 21
A full set is 32 teeth, but some people do not have wisdom teeth (third molars)
Wisdom teeth emerge at years

4. Classification of Teeth
Incisors – chisel-shaped for cutting
Canines – fanglike (eyeteeth) for tearing or piercing
Premolars – bicuspids for grinding
Molars – for grinding

5. Human Deciduous & Permanent Teeth
Figure 14.9

6. Regions of a Tooth Crown – exposed part
Outer enamel (calcium) – hardest substance in the body
Dentin – found deep to the enamel and forms the bulk of the tooth
Pulp cavity – contains connective tissue, blood vessels, and nerve fibers
Root canal – where the pulp cavity extends into the root
Figure 14.10

7. Regions of a Tooth Neck Root Gingiva = gums
Region in contact with the gum
Connects crown to root
Root
Cementum – covers outer surface and attaches the tooth to the periodontal membrane
Periodontal membrane attached to the bone
Root canal carrying blood vessels and nerves
Gingiva = gums
Figure 14.10

8. Regions of a Tooth
Figure 14.10

9. Meth drug user

10. Salivary Glands
Three pairs of salivary glands empty secretions through tiny ducts into the mouth
Parotid glands – located anterior to ears
Will become inflammed if infected with mumps
Mumps is highly contagious
Complications can affect reproductive organs, pancreas
Submandibular glands
Sublingual glands

12. Saliva Mixture of mucus and serous fluids Helps to form a food bolus
Easier to chew & swallow
Contains salivary amylase to begin starch digestion
Contains lysozyme & IgA (kills bacteria)
Dissolves chemicals so they can be tasted

13. Pancreas Soft, pink, triangular
Extends across the abdomen from the spleen to duodenum
Retroperitoneal – lies posterior to parietal peritoneum

14. Pancreas
Produces a wide spectrum of digestive enzymes that break down all categories of food
Enzymes are secreted into the duodenum
Alkaline fluid introduced with enzymes to neutralize acidic chyme
Endocrine products of pancreas – released into blood-help regulate absorption of sugar by cells
Insulin
Glucagon

16. Pancreas
Figure 14.6

17. 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

18. Liver Diseases Hepatitis – viral infection
Cirrhosis – Chronic disease in which liver tissue gradually replaced by scar tissue
Caused by diseases such as hepatitis and alcoholism

19. Location of Liver
Figure 14.5

20. Livers: Normal, fatty, cirrhosis

21. Bile Produced by cells in the liver Chemical Composition
Bile salts-help break large fat globules into smaller ones
Bile pigment (mostly bilirubin from the breakdown of hemoglobin)
Cholesterol
Phospholipids—emulsifies fats
Electrolytes

22. Gall Bladder Sac found in hollow fossa of liver
When no digestion is occurring, bile backs up the cystic duct for storage in the gallbladder
When digestion of fatty food is occurring, bile is introduced into the duodenum from the gallbladder
Gallstones are crystallized cholesterol which can cause blockages

23. Gallbladder
Figure 14.6

24. Liver with Gall Bladder

25. Gall Stones

26. Functions 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 and relaxation that squeezes food along the GI tract
Segmentation—moving materials back and forth to aid with mixing in the small intestine

27. Peristalsis
Figure 14.12

28. Brain Break!! Betcha Can’t… (only 1 in 10 can do this!!)
Roll your head in one direction and roll your tongue around your lips in the opposite direction…
Reach out with straight arms, cross wrist, grasp hands…Reach up…arch back…come back…cross legs…spell your full name backwards

29. Functions of the Digestive System
Mechanical Digestion
Physically fragmenting food into smaller pieces
Mixing of food in the mouth by the tongue
Churning of food in the stomach
Segmentation in the small intestine
Mechanical digestion prepares food for further degradation by enzymes

30. Functions of the Digestive System
Chemical Digestion
Enzymes break down food molecules into their building blocks
Hydrolysis – water added to break bonds
Each major food group uses different enzymes
Carbohydrates are broken to simple sugars
Monosaccharide = glucose, fructose & galactose
Disaccharides = sucrose, maltose & lactose
Proteins are broken to amino acids
Fats are broken to fatty acids and alcohols

31. Functions of the Digestive System
Figure (1 of 3)

32. Figure (3 of 3)

33. Functions of the Digestive System
Absorption
End products of digestion are absorbed in the blood or lymph
By active or passive transport
Food must enter mucosal cells and then into blood or lymph capillaries
Defecation
Elimination of indigestible substances from the GI tract in the form of feces

34. Functions of the Digestive System

35. Control of Digestive Activity
Mostly controlled by reflexes via the parasympathetic division of autonomic nervous system
Parasympathetic fibers of cranial nerves V & IX
Chemical and mechanical receptors are located in organ walls that trigger reflexes
Stimuli receptors respond to include:
Stretch of the organ
pH of the contents
Presence of breakdown products
Reflexes include:
Activation or inhibition of glandular secretions
Smooth muscle activity

36. Digestive Activities of the Mouth
Mechanical breakdown
Food is physically broken down by chewing
Chemical digestion
Food is mixed with saliva
Breaking of starch into maltose by salivary amylase

37. Activities of the Pharynx & Esophagus
These organs have no digestive function
Serve as passageways to the stomach
Deglutition =Swallowing—occurs in two phases:
Buccal Phase
Involves tongue, soft palate, pharynx & esophagus
Voluntary control
Occurs in the mouth
Food is formed into a bolus
The bolus is forced into the pharynx by the tongue

38. Deglutition -Swallowing
Pharyngeal-Esophageal phase
Due to parasympathetic division of autonomic nervous system (vagus nerve)
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
Gravity plays NO part
The cardioesophageal sphincter is opened when food presses against it
Video Clip: Swallowing

39. Deglutition (Swallowing)
Figure 14.14a–b

40. Deglutition (Swallowing)
Figure 14.14c–d

41. Chemical Digestion in the Stomach
Gastric juice is regulated by neural and hormonal factors
Presence of food or rising pH causes the release of the hormone gastrin
Gastrin causes stomach glands to produce
Protein-digesting enzymes
Mucus
HCl
HCl makes the stomach contents very acidic
Acidic pH is necessary to:
Activate pepsinogen to pepsin for protein digestion
Provides a hostile environment for microorganisms
Mucus protects stomach
2-3L of gastric juice are produced every day

42. Digestion & Absorption in the Stomach
Protein digestion enzymes:
Pepsin – an active protein digesting enzyme
Rennin – works on digesting milk protein
Produced by infants, not adults
The only absorption that occurs in the stomach is of alcohol and aspirin

43. Propulsion in the Stomach
Food must first be well mixed
Rippling peristalsis occurs in the lower stomach
The pylorus meters out chyme into the small intestine (30 ml at a time)
The stomach empties in 4–6 hours
Vomiting = emesis (reverse peristalsis)
Figure 14.15

44. Propulsion in the Stomach
Figure 14.15a–c

45. Digestion in the Small Intestine
Takes 3-6 hours
Enzymes from the brush border
Break double sugars into simple sugars
Complete some protein digestion
Pancreatic enzymes play the major digestive function
Help complete digestion of starch (pancreatic amylase)
Carry out about half of all protein digestion (trypsin, chymotripsin, carboxypeptidase
Digest fats using lipases from the pancreas
Digest nucleic acids using nucleases
Alkaline content neutralizes acidic chyme
Pancreatic juice – HCO3 (pH 8.0); alkaline content neutralizes acidic chyme

46. Regulation of Pancreatic Juice Secretion
Release of pancreatic juice into the duodenum is stimulated by
Vagus nerve
Local hormones
Secretin & Cholecystokinin
Secreted by mucosal cells of small intestine
Travel to pancreas, liver & gall bladder
Hormones travel the blood to stimulate the pancreas to release enzyme- and bicarbonate-rich product
Figure 14.16

47. Regulation of Pancreatic Juice Secretion
Hormones travel the blood to stimulate the pancreas to release enzyme- and bicarbonate-rich product
Secretin causes the liver to increase bile output
CCK causes the gallbladder to release stored bile
Bile is necessary for fat absorption and absorption of fat-soluble vitamins (K, D, A)

48. Regulation of Pancreatic Juice Secretion
Figure 14.16

49. Hormones & Hormonelike Products that Act in Digestion
Table 14.1 (1 of 2)

50. Hormones & Hormonelike Products that Act in Digestion
Table 14.1 (2 of 2)

51. Absorption in the Small Intestine
Water is absorbed along the length of the small intestine
End products of digestion
Most substances are absorbed by active transport through cell membranes
Lipids are absorbed by diffusion into capillaries & lacteals
Substances are transported to the liver by the hepatic portal vein or lymph

52. Propulsion in the Small Intestine
Peristalsis is the major means of moving food
Segmental movements:
Mix chyme with digestive juices
Aid in propelling food

53. Digestion & Absorption in the Large Intestine
Complete digestion takes approximately hours
No digestive enzymes are produced
Resident bacteria digest remaining nutrients
Produce some vitamin K and B
Release gases – methane & hydrogen sulfide (500ml/day)
Water and vitamins K and B are absorbed
2L of water are absorbed
Remaining materials are eliminated via feces
Feces contains:
Undigested food residues
Mucus
Bacteria & Water

54. Propulsion in the Large Intestine
Sluggish Peristalsis
Mass movements
Slow, powerful movements
Occur three to four times per day – during or just after eating
Presence of feces in the rectum causes a defecation reflex
Spinal (sacral) reflex
Internal anal sphincter is relaxed

55. Defecation occurs with relaxation of the voluntary (external) anal sphincter
Increased fiber causes increased colon contractions & softens stool
Diarrhea – food rushes through, no water absorption
Constipation – food remains too long, too much water is absorbed