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Nicky Digestion BMS192 > Digestion > Flashcards

Digestion Flashcards

1
Q

What structures make up the digestive system and what are their functions?

A
  • oral cavity, teeth, tongue
    Mechanical processing, moistening, mixing with salivary secretions
  • pharynx
    Muscular propulsion of materials into the esophagus
  • esophagus
    Transport of materials to the stomach
  • stomach
    Chemical breakdown of materials by acid and enzymes; mechanical processing through muscular contractions
  • small intestine and large intestine
    Enzymatic digestion and absorption of water, organic substrates, vitamins and ions
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2
Q

What are the accessory organs of the digestive system?

A
  • salivary glands
    Secretion of lubricating fluid containing enzymes that breakdown carbohydrates
  • liver
    Secretion of bile (important for lipid digestion), storage of nutrients, and many other vital functions
  • gallbladder
    Storage and concentration of bile
  • pancreas
    Exocrine cells secrete buffers and digestive enzymes; endocrine cell secrete hormones
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3
Q

What are the 4 layers of the digestive system tissue?

A
  • mucosa
  • sub mucosa
  • muscularis externa
  • serosa
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4
Q

What is the peritoneum?

A
  • blood vessels and nerves reach the small and large bowel through the mesenteries
  • enables folding of the lengths of bowel into the abdominal space whilst keeping these vessels and nerves untangled
  • provides serous fluid, minimising friction due to movement within the lumen
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5
Q

What is mechanical and chemical digestion?

A

MECHANICAL

  • through chewing and muscular action, the food is broken down in to smaller pieces until it has a fluid like consistency
  • as it leaves the stomach, what was food is now called chyme

CHEMICAL
The addition of enzymes to the food causes chemical bonds to be broken.
- proteins become their component amino acids
- starches and larger polysaccharide sugars become monosaccharides
- larger lipid molecules become smaller component molecules

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6
Q

How does food move through the GI tract?

A
  • swallowing into the esophagus - peristalsis
  • churning in the stomach
  • expulsion in to the small intestine ( small bowel) by peristalsis
  • mass movement in the large colon ( large bowel)
  • defecation from the anus
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7
Q

How is the function of and movement within the GI tract controlled?

A
  1. Local factors
    - primary stimulus for digestive activities
    Eg. PH of contents in the lumen, physical distortion of digestive tract wall, presence of chemicals
  2. Neural control mechanism
    SHORT REFLEXES
    - myenteric plexus neurone to local changes
    LONG REFLEXES
    - interneurones and motor neurones of CNS generally controlling movement from one digestive tract region to another
  3. Hormonal control mechanism
    - peptides produced by enteroendocrine cells within epithelium of digestive tract
    - at least 18 hormones that effect digestive and other systems
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8
Q

What role does the mouth and it’s structures play in digestion?

A

HARD PALATE
underlain with bone, hard surface to aid with mechanical digestion

SOFT PALATE
Skeletal muscle, rise to close off nasopharynx when we swallow

TONGUE
skeletal muscle and mucous membrane
Papillae- taste buds grip and repositions food, mixes food with saliva and form bolus.
Forms words

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9
Q

What are the main functions of saliva?

A
  • Salivary glands add enzymes to the food and moisten it
  • salivary amylase begins starch digestion
  • mucous moistens food
  • antibodies and proteins released for immune protection
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10
Q

How is food swallowed - BUCCAL PHASE

A
  • Compression of the bolus against the hard palate.
  • tongue retracts, forces bolus into oropharynx and assists in elevation of soft palate, sealing of nasopharynx
  • buccal phase is voluntary
  • once bolus enters oropharynx, reflex responses are initiated and bolus is moved toward the stomach
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11
Q

What is the overarching role of the digestive system?

A

BREAKS DOWN INGESTED FOOD FOR USE BY THE BODY

  • chemical breaking of bonds releases energy and helps to maintain body temperature
  • rebuilding the food molecules into those needed by the body requires energy.

EXCRETES WASTE PRODUCTS AND UNDIGESTIBLE FIBRE AS FAECES THROUGH THE PROCESS OF DEFAECATION

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12
Q

How is food swallowed - PHARYNGEAL PHASE

A

Begins with receptors on palatial arches and uvula are stimulated. Motor commands from swallowing centre in the medulla oblongata then direct a coordinated pattern of muscle contraction in pharyngeal muscles. Elevation of the larynx and folding of epiglottis results from contraction of the pharyngeal muscles, while palatial muscles elevate uvula and soft palate to block the entrance of the nasopharynx. Pharyngeal constrictions force bolus through pharynx, past the close epiglottis and in to the esophagus.

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13
Q

How is food swallowed? - OESOPHAGEAL PHASE

A

Begins as contraction of pharyngeal muscles forces the bolus though the entrance to oesophagus. Bolus is then pushed towards stomach by peristalsis. Approach of bolus triggers the opening on the lower oesophageal sphincter, and the bolus then continues to the stomach

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14
Q

What are the main functions of the oesophagus?

A
  • passes through the diaphragm and terminates at oesophageal sphincter

Digestive functions of the oesophagus
- muscles secreted and muscular contractions propel food into the stomach

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15
Q

What are the functions of the stomach?

A
  • mixing chamber and storage area for ingested food
  • rugby allow for increased volumes
  • pyloric sphincter regulates movement of chyme into the small intestine
  • site of mechanical and chemical digestion

MECHANICAL
mixing waves causes peristalsis

CHEMICAL
formation of hydrochloric acid

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16
Q

What are the main stomach secretions and role in digestion?

A

MUCOUS EPITHELIAL CELLS
- simple squamous epithelium that produces alkaline mucous to protect epithelial cells from acids and enzymes

PARIETAL CELLS

  • secrete intrinsic factor and HCI
  • intrinsic factor aids B12 absorption
  • HCI activates pepsinogen (keeps stomach at pH 2)

CHIEF CELLS

  • secrete pepsinogen
  • activates in acid to become pepsin
  • activates proteolytic (protein binding) enzyme

G CELLS

  • release gastric hormones in to blood in response to muscle stretch receptors and chemical receptors
  • produce a variety of hormones
17
Q

How is digestion controlled in the stomach?

A 
CEPHALIC PHASE
- you see, smell, taste
- signal from CNS to Autonomic NS
- vagus nerve stimulates mucous cells, chief cells, parietal cells and G cells
- results in mucous cells releasing mucous
   ~ chief cells = pepsinogen 
   ~ parietal cells = HCI
   ~ G cells = gastrin

GASTRIC PHASE

  • food arrives at stomach
  • causes distension, pH increases
  • distension and increased pH stimulates receptors that cause increased cell secretions and mixing wave
  • peptides and amino acids in chyme stimulates secretion of hormone gastrin.

INTESTINAL PHASE

  • chyme enters small intestine
  • in the stomach, contents are moving toward the small intestine, so there is no more distension and no more stimulation of stretch receptors
  • stretch receptors and chemoreceptors of duodenum stimulated. This triggers enterogastric reflexes
  • enterogastric reflexes inhibits gastrin production and gastric contractions and stimulates contractions of pyloric sphincter
18
Q

What is the main role of the liver?

A

Metabolism of:
~carbohydrates
~lipids
~proteins

  • processes drugs and hormones
  • excretes bilirubin
  • synthesis of bike salts and bile
  • storage of glycogen, vitamins and minerals
  • phagocytosis
  • activates vitamin D
19
Q

What is the main role of the gall bladder?

A

Secretes bile to emulsify lipid droplets

20
Q

What is the main role of the pancreas?

A
  • pancreatic islets (of langerhans)
  • glucagon: increases rate of glycogen to glucose conversion
  • insulin: fir glucose storage
  • somatostatin: slows down digestion by inhibiting digestion and absorption
21
Q

What is the structure of the small intestine?

A
  • main role is digestion and absorption
  • 6m in length
  • divided into sections
    ~ duodenum
    ~ jejunum
    ~ ileum
  • connected to large intestine by ileocaecal sphincter
22
Q

How is the small intestine adapted for digestion and absorption?

A
  • brush border enzymes
  • accepts bike and pancreatic secretions
  • large surface area
  • good blood supply and lymphatic capillaries
23
Q

What is the structure of the large intestine?

A

Colon

  • ascending
  • transverse
  • descending
  • sigmoid

CAECUM

  • pouch
  • attached appendix

RECTUM

ANAL CANAL

  • anal columns
  • anus
  • internal and external sphincter
24
Q

What are the major roles of the large intestine?

A
  • production and storage of faeces
  • water reabsorption to produce semi-dried chyme
  • absorption of bacterial products and vitamins
25
Q

What is faeces?

A

Semi- dried chyme, inorganic salts, mucous, bacteria, undigested components and wastes from liver

26
Q

What are the major roles of bacteria in the large intestine?

A
  • ferment carbohydrates
  • excessive gases produced as flatus or flatulence
  • breakdown proteins
  • decompose bilirubin
  • produce some vitamins (k, B5, biotin)
27
Q

How is water added into and removed from GI tract?

A
  • added through oral intake
  • reabsorption in small intestine
  • lost through defacation
28
Q

Where within the GI tract does most digestion take place?

A

MOUTH
- amylase starts carbohydrate digestion

STOMACH
- hydrochloric acid and pepsin break down large proteins

SMALL INTESTINE
- pancreatic enzymes released to duodenum and the small intestine itself continue to break down carbohydrates and proteins and also help break down lipids

29
Q

Where in the GI track does most absorption take place?

A

Majority in the small intestine

30
Q

Where are the salivary glands?

A
  • sublingual
  • submandibular
  • parotid
31
Q

What are the roles of the salivary gland secretions?

A

SALIVARY AMYLASE
- commences breakdown of starches

SALIVARY LIPASE
- activated in stomach to assist in lipid breakdown

DEFENSINS
- proteolytic enzymes that kill bacteria in food

MUCOUS

32
Q

Where is the liver?

A

Sits on the right side of the stomach

33
Q

Where is the gall bladder? What is the function of bile?

A
  • under the liver in the upper right section of abdominal cavity
  • releases bile via the cystic duct, into the small intestine to help breakdown food
34
Q

Where is the pancreas?

A

Located posterior to stomach

35
Q

What are the roles of exocrine pancreatic secretions?

A

PANCREATIC JUICES

  • 1200 - 1500ml per day
  • pH 7.1-8.2
  • water
  • salts
  • sodium bicarbonate (neutralises stomach acid in chyme)
  • enzymes(pancreatic amylase, lipase, trypsinogen)
36
Q

What are the 6 main types of nutrients?

A 
Water
Carbohydrates
Lipids
Proteins
Minerals
Vitamins
37
Q

Metabolism

A

All chemical reactions in the body

38
Q

Enzymes

A
  • catalyse chemical reactions

- may require coenzyme

39
Q

What are amino acids?

A

The building blocks for protein

Nicky Digestion BMS192 (1 decks)

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