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LSB142 Anatomy and Physiology > Digestive System > Flashcards

Digestive System Flashcards

1
Q

Functions of the digestive system

A
  • Ingestion—taking in food
  • Digestion—breaking food into nutrient molecules
  • Absorption—movement of nutrients into the bloodstream
  • Defecation—excretes to rid the body of indigestible waste
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2
Q

2 main groups of organs in Digestive System

A

o Digestive tract (gastrointestinal, or GI, tract)
 Continuous, coiled, hollow tube
 These organs ingest, digest, absorb, defecate
 Begins with the mouth  ends with the anus
o Accessory digestive organs
 Include teeth, tongue, and several large digestive organs
 Assist digestion in various ways
 Connected to the GI tract by ducts
• Secrete chemicals which aid in chemical breakdown and absorption of food

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3
Q

Organs of the digestive tract

A 
o	Mouth 
o	Pharynx 
o	Oesophagus 
o	Stomach 
o	Small / Large intestine 
o	Anus
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4
Q

Accessory organs

A
  • Salivary glands
  • teeth
  • Pancreas
  • Liver
  • Gallbladder
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5
Q

Name the components of the mouth

A
  • Mouth (oral cavity)
    o Mucous membrane–lined cavity
  • Lips (labia)
  • Cheeks
  • Hard palate
  • Soft palate
  • Uvula
  • Vestibule
  • Oral cavity proper
  • Tongue
  • Tonsils
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6
Q

Functions of the mouth

A
  • Mastication (chewing) of food
  • Tongue mixes masticated food with saliva
    o Chemical breakdown of food
  • Tongue initiates swallowing
    o Propulsion by pushing food to the pharynx
  • Taste buds on the tongue allow for taste
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7
Q

Describe the pharynx

A
  • Serves as a passageway for foods, fluids, and air
  • Food passes from the mouth posteriorly into the:
    o Nasopharynx
     Connects nasal cavity to the oropharynx
    o Oropharynx
     Posterior to oral cavity
     Foods, liquids and air passes through
    o Laryngopharynx
     Below the oropharynx and continuous with the oesophagus
  • Food is propelled to the oesophagus by two skeletal muscle layers in the pharynx
    o Longitudinal outer layer
    o Circular inner layer
  • Alternating contractions of the muscle layers (peristalsis) propel the food through pharynx inferiorly
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8
Q

Anatomy of oesophagus

A

o About 10 inches long
o Runs from pharynx to stomach through the diaphragm
o Passes through opening in diaphragm

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9
Q

Physiology of oesophagus

A

o Conducts food by peristalsis (slow rhythmic squeezing) to the stomach
 When food reaches the top of the oesophagus following swallowing  a wave of peristalsis beings  pushes food into the stomach
o Passageway for food only (respiratory system branches off after the pharynx)

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10
Q

What are the 4 layers of tissue in digestive tract organs

A

o Mucosa
o Submucosa
o Muscularis externa
o Serosa

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11
Q

Describe the mucosa

A
  • Innermost, moist membrane consisting of:
    o Surface epithelium that is mostly simple columnar epithelium
     Except for oesophagus — stratified squamous epithelium
     Covered in mucous secreted by cells or glands
    o Small amount of connective tissue (lamina propria)
     Contains blood vessels, lymphatic vessels and mucous secreting vessels (some parts of the body)
    o Scanty smooth muscle layer (thin)
  • Lines the cavity (known as the lumen)
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12
Q

Describe the submucosa

A
  • Just beneath the mucosa
  • Soft, irregular dense connective tissue with blood vessels, nerve endings, mucosa-associated lymphoid tissue, and lymphatic vessels
    o Glands and tissues secrete substances that aid in secretion and absorption
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13
Q

Explain the Muscularis Externa

A
  • Surrounds submucosal layer
  • Propels food through Digestive Tract by peristalsis
  • Performs mechanical digestion
    o Churns food
  • Has two layers:
    o Inner circular layer
    o Outer longitudinal layer

o Layer of nerve fibers between the layers regulate the activity of each layer

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14
Q

Describe the serosa

A
  • Thin, serous membrane which helps to reduce friction
  • Outermost layer of the wall
  • Contains fluid-producing cells
  • Divided into:
    o Visceral peritoneum
     Innermost layer that is continuous with the outermost layer
    o Parietal peritoneum
     Outermost layer that lines the abdominopelvic cavity by way of the mesentery
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15
Q

Name the Digestive tract nerve plexuses

A

2 intrinsic nerve plexuses that are part of the autonomic nervous system
o Submucosal nerve plexus
o Myenteric nerve plexus
Regulate mobility and secretory activity of the GI tract organs

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16
Q

Name the stomach regions

A

o Cardial (cardia)
 Near the heart and surrounds the cardio oesophageal sphincter (allows food to enter from oesophagus)
o Fundus
 Expanded portion lateral to the cardiac region
o Body
 Midportion
 Greater curvature is the convex lateral surface
 Lesser curvature is the concave medial surface

o Pylorus
 Funnel-shaped terminal end
 Continuous with small intestine through the pyloric sphincter or pyloric valve

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17
Q

Anatomy of the stomach

A
  • C-shaped organ located on the left side of the abdominal cavity
  • Stomach can stretch and hold 4 L (1 gallon) of food when full
  • Varies from 15 – 25 cm in length
  • Diameter and volume depend on how much food it contains
    o Rugae
     Internal folds of the mucosa present when the stomach is empty
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18
Q

What is the stomach omentum

A
  • Lesser Omentum
    o Double layer of the peritoneum
    o Extends from liver to the lesser curvature of stomach
  • Greater Omentum
    o Another extension of the peritoneum
    o Covers the abdominal organs and attaches to posterior boy wall
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19
Q

Structure of the stomach mucosa and cells

A
  • Simple columnar epithelium composed almost entirely of mucous cells
  • Mucous cells produce bicarbonate-rich alkaline mucus
    o Clings to the stomach mucosa and protections from damage against acid
  • Chief cells
    o Produce inactive protein-digesting enzymes (pepsinogens)
  • Parietal cells
    o Produce hydrochloric acid that activates enzymes
     Conversion of pepsinogen and pepsin
    o Makes stomach contents acidic
  • Mucous neck cells
    o Produce thin acidic mucus (different from the mucus produced by mucous cells of the mucosa) with an unknown function
  • Enteroendocrine cells
    o Produce local hormones such as gastrin
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20
Q

Stomach functions

A
  • Temporary storage tank for food
  • Site of food breakdown
    o Three layers of muscle allow to move food along tract and breakdown
  • Chemical breakdown of protein begins
    o Most occurs within the pyloric region
  • Delivers chyme (thick) (processed food) to the small intestine via the pyloric sphincter
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21
Q

Describe the small intestine

A
  • The body’s major digestive organ
  • Longest portion of the digestive tract (2–4 m, or 7–13 feet, in a living person)
  • Site of nutrient absorption into the blood and all water absorption
  • Muscular tube extending from the pyloric sphincter to the ileocecal valve
  • Suspended from the posterior abdominal wall by the mesentery
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22
Q

Small intestine subdivisions

A
  • Duodenum (5%)
  • Jejunum (40%)
  • Ileum (60%)
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23
Q

Describe chemical digestion in the small intestine

A
  • Begins in the small intestine  can only process a small amount of food at a time  pyloric sphincter controls movement of chyme into small intestine  prevents small intestine from being overwhelmed
  • Enzymes produced by intestinal cells and pancreas are carried to the duodenum by pancreatic ducts
    o Chemical breakdown of food ends in the pancreatic ducts
24
Q

Small Intestine Structural Modifications

A
  • Increase surface area for food absorption
  • Decrease in number toward the end of the small intestine
    o Villi
     Finger like projections formed by the mucosa
    • House a capillary bed and lacteal
     Contains tubular indentations (intestinal crypts)
     Each contain a lymphatic capillary (lacteal) as well as blood capillaries
    o Microvilli
     Tiny projections of the plasma membrane (brush border enzymes)
    o Circular folds (plicae circulares)
     Deep folds of mucosa and submucosa
25
Q

Peyer’s patches

A
  • Collections of lymphatic tissue
  • Located in submucosa
  • Increase in number toward the end of the small intestine
  • More are needed there because remaining food residue contains much bacteria
    o Must be prevented from entering the blood stream
26
Q

Large Intestine positioning and features

A
  • Larger in diameter, but shorter in length at 1.5 m, than the small intestine
  • Extends from the ileocecal valve to the anus
     Presence of large colon ease bacteria
    • Responsible for B vitamin synthesis and Vitamin K
27
Q

Large intestine functions

A

propulsion and elimination of waste

- Absorption of water, electrolytes and some vitamins are additional but limited functions

28
Q

Subdivisions of large intestine

A 
o	Cecum
o	Appendix 
o	Colon 
o	Rectum
o	Anal canal
29
Q

Cecum

A
  • Saclike first part of the large intestine (first to receive food)
  • Connects to large intestine by the ileocecal valve
    o Usually, closed  opens in response to gastrin (released by the stomach)
    o Partially controlled by the nervous system
    o When open  digestive remnants of food travel from the ileum to the cecum
30
Q

Appendix

A

o Hangs from the cecum
o Accumulation of lymphoid tissue that sometimes becomes inflamed (appendicitis)
 Contains lymphocytes that help protect the body from infection organisms
• Does not protect against appendicitis

31
Q

Describe the colon

A

Ascending
o Travels up right side of abdomen and makes a turn at the right colic (hepatic) flexure

Transverse
o Travels across the abdominal cavity and turns at the left colic (splenic) flexure

Descending
o Travels down the left side

Sigmoid
o S-shaped region; enters the pelvis  exits at the rectum
- Sigmoid colon, rectum, and anal canal are located in the pelvis

32
Q

Describe the anal canal and anus

A
  • Anal canal ends at the anus
  • Anus
    o Opening of the large intestine
    o External anal sphincter
     Formed by skeletal muscle and is voluntary
    o Internal anal sphincter
     Formed by smooth muscle and is involuntary
    o These sphincters are normally closed due to constriction except during defecation
  • The large intestine delivers indigestible food residues to the body’s exterior
33
Q

Describe the salivary glands

A
  • Three pairs of salivary glands empty secretions into the mouth
  • Located within tissue surrounding the oral cavity
    o Parotid glands (largest)
     Found anterior to the ears
     Mumps affect these salivary glands
    o Submandibular glands
     Lie on the medial side of the mandible
    o Sublingual glands
     Both submandibular and sublingual glands empty saliva into the floor of the mouth through small ducts
34
Q

Describe the Saliva

A
  • Mixture of mucus and serous fluids
  • Composed mostly of water
  • Helps to moisten and bind food together into a mass called a bolus
  • Contains:
    o Salivary amylase
     Begins starch digestion
     Breaks down complex carbohydrates into shorter chains of sugar chains
    o Lysozymes and antibodies
     Inhibit bacteria
    o Lingual lipase
     Initiates the breakdown of fats
  • Dissolves chemicals so they can be tasted
35
Q

Describe the pancreas

A
  • Functions as an exocrine and endocrine gland
  • Soft, pink triangular gland
  • Found posterior to the parietal peritoneum
    o Mostly retroperitoneal
  • Secretes products into the blood and lumen
  • Extends across the abdomen from spleen to duodenum
  • Produces a wide spectrum of digestive enzymes that break down all categories of food
  • Secretes enzymes and pancreatic juice into the duodenum
    o Pancreatic juices contain digestive enzymes (proteases  break down proteins / amylases  breaks down starches / lipases  break down lipids)
  • Alkaline fluid introduced with enzymes neutralizes acidic chyme coming from stomach
  • Hormones produced by the pancreas
    o Insulin
    o Glucagon

o Involved in regulating blood glucose levels

36
Q

Describe features of the liver

A
  • 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
37
Q

Liver’s role to produce bile

A
  • Bile leaves the liver through the common hepatic duct and enters duodenum through the bile duct
    o Duodenum uses bile to breakdown lipids
  • Bile is yellow-green, watery solution containing:
    o Bile salts and bile pigments (mostly bilirubin from the breakdown of hemoglobin)
     Are emulsifying agents  greatly increases surface area of fats and assisting breakdown by lipase enzymes

o Makes about 1L/day at a constant rate  only needed following food intake
- Bile emulsifies (breaks down) fats

38
Q

Describe the gall bladder

A
  • Green sac found in a shallow fossa in the inferior surface of the liver
    o Releases bile after a meal that contains fat
     Controlled by several bile sphincters (bile sphincters, pancreatic sphincter and hepatopancreatic sphincter)
    o When no digestion is occurring, bile backs up the cystic duct for storage in the gallbladder
    o While in the gallbladder, bile is concentrated by the removal of water
    o When chyme containing fat enters the duodenum  gallbladder contracts  the gallbladder spurts out stored bile
     Common bile duct and hepatopancreatic duct sphincter relax to allow bile to flow to duodenum and emulsify the fat
39
Q

What is propulsion

A

 Movement of foods from one region of the digestive system to another

40
Q

What is Ingestion

A

 Placing of food into the mouth

41
Q

Explain food breakdown: mechanical breakdown

A

• 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

42
Q

Food breakdown: digestion

A

 Digestion occurs when enzymes chemically break down large molecules into their building blocks
 Each major food group uses different enzymes
• Carbohydrates are broken down to monosaccharides (simple sugars)
• Proteins are broken down to amino acids
• Fats are broken down to fatty acids and glycerol

43
Q

Absorption

A

 End products of digestion are absorbed in the blood or lymph
 Food must enter mucosal cells and then move into blood or lymph capillaries

44
Q

Defecation

A

 Elimination of indigestible substances from the GI tract in the form of feces

45
Q

Food breakdown

A

Presence of food or rising pH causes the release of the hormone gastrin
o Gastrin causes stomach glands to produce:
 Protein-digesting enzymes (pepsin), active protein digesting enzyme (renin)
 Mucus
 Hydrochloric acid
o Hydrochloric acid makes the stomach contents very acidic
o Acidic pH
 Activates pepsinogen to pepsin for protein digestion
 Provides a hostile environment for microorganisms
• Works on digesting milk protein in infants; not produced in adults
o Alcohol and aspirin are virtually the only items absorbed in the stomach

46
Q

Food propulsion

A
  • Peristalsis:
    o Waves of peristalsis occur from the fundus to the pylorus, forcing food past the pyloric sphincter
  • Grinding:
    o The pylorus meters out chyme into the small intestine (3 ml at a time)
  • Retropulsion:
    o Peristaltic waves close the pyloric sphincter, forcing contents back into the stomach; the stomach empties in 4–6 hours

• Segmentation
o Movement of materials back and forth to foster mixing in the small intestine

47
Q

Activities of the Small Intestine

A
  • Chyme breakdown and absorption
    o Intestinal enzymes from the brush border function to:
     Break double sugars into simple sugars
     Complete some protein digestion
    o Intestinal enzymes and pancreatic enzymes help to complete digestion of all food groups
    o Pancreatic enzymes play the major role in the digestion of fats, proteins, and carbohydrates
    o Alkaline content neutralizes acidic chyme and provides the proper environment for the pancreatic enzymes to operate
48
Q

Release of pancreatic juice from the pancreas into the duodenum is stimulated by

A

 Vagus nerves
 Local hormones that travel via the blood to influence the release of pancreatic juice (and bile)
• Secretin
• Cholecystokinin (CCK)
o Hormones (secretin and CCK) also target the liver and gallbladder to release bile
 Bile
• Acts as a fat emulsifier
• Needed for fat absorption and absorption of fat-soluble vitamins (K, D, E, and A)
o Water is absorbed along the length of the small intestine
o End products of digestion

49
Q

Activities of the large intestine - nutrient breakdown and absorption

A

o No digestive enzymes are produced
o Resident bacteria digest remaining nutrients
 Produce some vitamin K and some B vitamins
 Release gases
o Water, vitamins, ions, and remaining water are absorbed
o Remaining materials are eliminated via feces

50
Q

Activities of the large intestine - Propulsion of food residue and defacation

A

o Sluggish peristalsis begins when food residue arrives
o Haustral contractions are the movements occurring most frequently in the large intestine
o Mass movements are slow, powerful movements that occur three to four times per day
o Presence of feces in the rectum causes a defecation reflex
 Internal anal sphincter is relaxed
 Defecation occurs with relaxation of the voluntary (external) anal sphincter

51
Q

Disorders of the digestive system

A 
-	Gastroesophageal reflux
o	Movement of chyme from stomach into lower oesophagus 
-	Ulcers
o	Break in the protective lining of the stomach, duodenum or lower oesophagus 
-	Gastroenteritis
o	Inflammation of the stomach or intestine 
-	Inflammatory bowel disease 
o	Ulcerative colitis
o	Chrohn’s disease
-	Constipation and diarrhoea 
-	Hepatitis 
-	Pancreatitis
-	Gallstones
52
Q

Explain the lips

A 
Protect the anterior opening
o	Assist with injection by grabbing food and pulling into mouth
o	Under voluntary control 
o	Stops food or liquid from leaking out
o	Made of orbicularis oris
53
Q

Explain the Cheeks, hard palate, soft palate, uvula, oral cavity proper and vestibule

A

Cheeks
o Form the lateral walls of oral cavity

  • Hard palate
    o Forms the anterior roof of oral cavity
    o Made of maxilla and palatine bones
  • Soft palate
    o Forms the posterior roof oral cavity
    o Formed from a fold of mucous membrane
  • Uvula
    o Fleshy projection of the soft palate
    o Helps prevent food from entering nasal cavity when swallowing
  • Vestibule
    o Space between lips externally and teeth and gums internally
  • Oral cavity proper
    o Area contained by the teeth
54
Q

Explain the tonsils

A 
Part of the bodies defence system 
o	Palatine
	Located at posterior end of oral cavity 
o	Lingual
	Located at the base of the tongue
55
Q

Explain the tongue

A

Attached at hyoid bone and styloid processes of the skull, and by the lingual frenulum to the floor of the mouth
o Lingual Frenulum  anchors tongue to floor of mouth and limits posterior movements

LSB142 Anatomy and Physiology (15 decks)

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