Chapter 24 - Digestive System Flashcards Preview

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Flashcards in Chapter 24 - Digestive System Deck (69):
1

(2) groups of organs compose digestive system

Gastrointestinal (GI) tract 

Accessory digestive organs

2

Gastrointestinal (GI) tract 

 

mouth, most of pharynx, esophagus, stomach, small intestine & large intestine

 

 

3

Accessory digestive organs

teeth, tongue, salivary glands, liver, gallbladder & pancreas

4

(6) functions of digestive system

ingestion 

secretion of water, acid, buffers & enzymes into lumen

mixing & propulsion 

digestion (mechanical & chemical) 

absorption

defecation

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(4) LAYERS of GI Tract

Mucosa

Submucosa

Muscularis

Serosa

 

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Mucosa - inner lining 

epithelium - protection, secretion & absorption

lamina propria - CT with blood & lymphatic vessels & MALT

muscularis mucosae - thin layer of folded smooth muscle 

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Submucosa

CT binding mucosa to muscularis

contains many blood & lymphatic vessels

submucosal plexus - network of neurons

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Muscularis

voluntary skeletal muscle in pharynx, mouth, upper 2/3 of esophagus & anal sphincter 

involuntary smooth muscle elsewhere 

arranged in inner circular fibers outer longitudinal fibers 

myenteric plexus between muscle layers

 

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Serosa

outermost covering of organs suspended in abdominopelvic cavity

also called visceral peritoneum

esophagus lacks serosa - has adventitia 

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Neural Innervation (2) 

Enteric Nervous system 

Autonomic nervous system

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enteric nervous sytem 

intrinsic set of nerves - "brain of gut"

neurons extending from esophagus to anus 

(2) plexuses

myenteric (GI tract motility) 

- submucosal (controlling secretions) 

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Autonomic Nervous system

extrinsic set of nerves

Parasympathetic stimulation - increases secretion & activity by stimulating ENS

Sympathetic stimulation - decreases secretion & activity by inhibiting ENS

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Peritoneum

divided into? (2) 

largest serous membrane of body

parietal - lines wall of cavity

visceral (aka serosa) - covers organs 

 

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(5) major peritoneal folds

greater omentum

falciform ligament

lesser omentum

mesentery 

mesocolon

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Oral Cavity 

formed by?

cheeks, hard & soft palates & tongue 

 

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Oral cavity proper

space from gums & teeth to fauces (opening between oral cavity & oropharynx) 

 

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(3) pairs of major salivary glands secrete most of saliva

parotid

submandibular

sublingual

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Salivation controlled by?

parasympathetic stimulation

sympathetic stimulation

ANS 

parasympathetic stimulation - promotes secretion

sympathetic stimulation - decreases salivation

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Teeth - (3) major regions 

crown 

root 

neck 

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Dentin of crown covered by ___

enamel

 

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2 sets of teeth 

deciduous (baby teeth) 

permanent teeth 

 

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Mechanical Digestion in mouth

chewing

tongue, teeth, saliva

forms bolus

 

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Chemical Digestion

salivary amylase - secreted by salivary glands acts on starches

inactived by stomach acid

lingual lipase - secreted by lingual glands of tongue acts on triglycerides 

activated in acidic environment of stomach

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Pharynx 

(3) parts 

food passes from mouth into pharynx

nasopharynx - respiration

oropharynx - digestive & respiratory

laryngopharynx - digestive & respiratory

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Esophagus 

secretes mucous, transports food - no enzymes produced, no absorption

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Esophagus 

1) mucosa

2) submucosa

3) muscularis 

4) adventitia

1) protection against wear & tear

2) ---

3) divided into third

superior - skeletal

middle - skeletal & smooth

inferior - smooth

2 sphincters 

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(2) sphincters in esophagus muscularis 

Upper esophageal sphincter (UES) - regulates movement into esophagus

Lower esophageal sphincter (LES) - regulates movement into stomach

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Swallowing involves (3) 

(3) stages

mouth, pharynx, esophagus

voluntary - bolus → oropharynx

pharyngeal - pharynx → esophagus

esophageal - esophagus → stomach 

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Stomach

(4) main regions

cardia

fundus

body 

pyloric part - pyloric antrum, pyloric canal, pylorus 

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Stomach mucosa

gastric glands open into gastric pits 

(3) types of exocrine gland cells 

- mucous neck cells, parietal cells, chief cells (pepsinogen & gastric lipase) 

G cell - endocrine cell - secretes gastrin

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Muscularis of Stomach

additional 3rd inner oblique layer

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Serosa

part of visceral peritoneum

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Mechanical Digestion 

mixing waves - creates chyme

 

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Chemical Digestion

- gastric juice 

parietal & chief cells

digestion of salivary amylase 

inactivated by acidic gastric juice - activates lingual lipase (digest triglycerides into FAs & diglycerides) 

Parietal cells- secrete HCl (kills microbes & denatures proteins) 

pepsin secreted by chief cells (digests proteins) 

gastric lipase splits triglycerides into FAs & monoglycerides

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Pancreas 

lies posterior to greater curvature of stomach 

pancreatic juice secreted into pancreatic duct & accessory duct to small intestine

 

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pancreatic duct joins __ ___ __ and enters ___ at ___ ___ 

common bile duct 

duodenum

hepatopancreatic ampulla

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Histology of Pancreas

99% of cells are acini

- exocrine 

- secrete pancreatic juice 

1% of cells are pancreatic islets (Islets of Langerhans) 

- endocrine

- secretes hormones glucagon, insulin, somatostatin, pancreatic polypeptide 

38

Liver 

composed of (3) 

heaviest gland of body

1) hepatocytes

2) bile canaliculi 

3) hepatic sinusoids

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1) hepatocytes

 

major functional cells of liver 

secrete bile

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2) bile canaliculi 

exits liver as?

ducts between hepatocytes that collect bile 

common hepatic duct → cystic duct from gallbladder → common bile duct

 

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Hepatic Sinusoids

highly permeable blood capillaries recieving oxygenated blood from hepatic artery & deoxygenated blood from hepatic portal vein

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Gallbladder 

contraction of smooth muscle fibers eject contents of gall bladder into ?

cystic duct 

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Functions of Gallbladder 

store & concentrate bile produced by liver until it is needed in small intestine

 

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Hepatic Blood Flow

liver recieves blood from:

hepatic artery carrying oxygenated blood

hepatic portal vein carries deoxygenated blood 

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Small Intestine

(3) regions

duodenum 

jejunum

ileum

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Mucosa of Small Intestine

absorptive cells

goblet cells 

intestinal glands

paneth cells

enteroendocrine cells 

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Submucosa of Small intestine

dudenal glands secrete alkaline mucus 

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Duodenum 

recieves stomach contents, pancreatic juice & bile 

neutralize stomach acid, emulsifies fats, pepsin inactivated by pH increase, pancreatic enzymes 

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Jejunum

most digestion & nutrient absorption occur here

 

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Ileum

has peyers patch - clusters of lymphatic nodules 

ends at ileocecal junction with large intestine

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Special structural features of small intestine

circular folds - permanent ridge of mucosa & submucosa

causes chyme to spiral 

Villi - contains arteriole, venule, capillary & lacteal 

Microvilli - projections of absorptive cells 

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Brush Border Enzymes

inserted into plasma membrane of absorptive cells

 

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Mechanical Digestion 

governed by?

segmentations

 

myenteric plexus

localized mixing contractions 

mix chyme & bring it in contact with mucosa for absorption

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Chemical Digestion

1) carbohydrates 

2) proteins

1) pancreatic amylase 

a-dextrinase, sucrase, lactase, maltase in brush border

2) trypsin, chymotrypsin, carboxypeptidase & elastase from pancreas 

aminopeptidase & dipeptidase in brush border

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Lipid Digestion

emulsification by __ __ increases surface area

triglyceride digestion 

bile salts

amphipathic - hydophobic & hydrophilic regions

 

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Nucleic Acids

 

ribonuclease & deoxyribonuclease in pancreatic juice

nucleosidases & phosphatases in brush border 

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Absorption of:

1) Monosaccharides

2) Amino acids

1) facilitated diffusion or active transport

2) active transport 

58

Large Intestine

(4) major regions

cecum

rectum

colon

anal canal

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Large Intestine 

ileocecal sphincter 

ileocecal sphincter - between small & large intestine 

 

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Colon divided into (4) 

ascending, transverse, descending & sigmoid 

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opening of anal canal (anus) guarded by ?

internal anal sphincter of smooth muscle & external anal sphincter of skeletal muscle

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Anatomy of large intestine 

Mucosa - mostly absorptive & goblet cells

no circular folds or villi

has microvilli

Submucosa

Muscularis - longitudinal muscle modified to form teniae coli

forms baustria - pouches

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Large Intestine begins as __ & __ in lower right corner

cecum & appendix

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Digestion of Large Intestine 

1) mechanical digestion

2) chemical digestion

1) haustral churning

peristalsis 

mass peristalsis

2) bacterial action, no enzymes

 

65

Anatomy of Anal Canal

anal columns

hemorrhoids

anal columns - longitudinal ridges seperated by mucus secreting anal sinuses

hemorrhoids - permanently distended veins

66

Defecation

stretching of rectum 

intrinsic defecation reflex via myenteric plexus → muscularis contracts & internal sphincter relaxs

 

parasympathetic defecation reflex via spinal cord 

stretching of rectum → sensory signals to spinal cord →splanchnic nerves return signals 

67

Defecation occurs only if ?

external anal sphincter is voluntarily relaxed 

68

abdominal contractions increase abdominal pressure as...

levator ani lifts anal canal upwards 

feces will fall away 

69