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a&p > Digestive/Nutrition & Metabolism > Flashcards

Digestive/Nutrition & Metabolism Flashcards

0
Q

what is ingestion?

A

introduction of solids & liquids in the oral cavity

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1
Q

What are the 6 main functions of the digestive system?

A 
ingestion
motility
secretion
digestion
absorption
elimination
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2
Q

what is motility?

A

voluntary & involuntary muscle contractions for mixing & moving materials through GI tract

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3
Q

what is secretion in the digestive process?

A

process of producing & releasing fluid products like digestive enzymes, acid, and bile into GI tract
facilitates digestion

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4
Q

what is digestion?

A

the breakdown of ingested food into smaller structures that can be absorbed from GI tract.

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5
Q

what are the 2 types of digestion?

A

mechanical - physically breaking down materials by chewing & mixing without changing chemical structure
chemical - enzymes break chemical bonds - change larger molecules into smaller molecules that can be absorbed

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6
Q

what is absorption?

A

can be passive movement and active transport of digested molecules, electrolytes, vitamins & water from GI tract into blood or lymph

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7
Q

what is elimination?

A

expulsion of indigestible components

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8
Q

What are the 2 categories of organs in the digestive system?

A

those composing the GI tract (form a continuous tube - oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, anus)
accessory digestive organs - accessory digestive glands produce secretions (salivary glands, liver & pancreas), other organs (teeth, tongue, gallbladder - concentrates & stores secretions of the liver)

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9
Q

what is the GI tract tube composed of?

A 
tunics
from inner to outer
mucosa
submucosa
muscularis
adventitia (or serosa)
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10
Q

What are the layers of the mucosa?

A

epithelium
lamina propia
muscularis mucosae (thin layer)

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11
Q

what kind of epithelium lines the GI tract?

A

simple columnar for stomach, small intestine & large intestine (allows for secretion & absorption)
areas where abrasion may occur (esophagus) are lined by nonkeratinized stratified squamous epithelium

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12
Q

what is the lamina propia of the GI tract composed of?

A

areolar connective tissue
small blood vessels
nerves
lymphatic capillaries

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13
Q

what is the muscularis mucosae and what is its function?

A

thin layer of smooth muscle deep to lamina propia in mucosa tunic
causes slight movements in mucosa which
1) facilitate release of secretions from mucosa into the lumen
2) increase contact of materials w/in lumen w/mucosa - shakes stuff up

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14
Q

what is the submucosa composed of?

A

areolar and dense irregular CT
large blood vessels
lymph vessels
nerves

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15
Q

what is the submucosal nerve plexus?

A

fine branches of nerves that extend into mucosa along w/their associated ganglia
also called Meissner plexus
innervate smooth muscle and glands of mucosa and submucosa

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16
Q

what is in the areolar CT of lamina propia of mucosa and submucosa?

A

MALT mucosa-associated-lymphatic tissue

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17
Q

what are Peyer patches?

A

aggregates of lymphatic nodules in submucosa of last region of small intestine (in the ileum)

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18
Q

what is the function of MALT?

A

helps prevent ingested microbes from crossing GI tract wall & entering body

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19
Q

what composes the muscularis?

A

2 layers of smooth muscle
inner circular layer - oriented circumferentially around GI tract
outer longitudinal layer - oriented lengthwise
axons and ganglia between these 2 layers - called myenteric nerve plexus (or Auerbach plexus) - control smooth muscle contractions

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20
Q

what is the enteric nervous system?

A

submucosal nerve plexus and myenteric nerve plexus

sensory neurons in these plexuses detect changes in GI tract wall & chemical makeup of contents of lumen

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21
Q

what kind of neurons compose the enteric nervous system?

A

sensory and motor neurons of the autonomic nervous system

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22
Q

what is a sphincter?

A

closes off the lumen along the GI tract to control the movement of materials in the next section of tract
a greatly thickened area in the inner circular muscular layer

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23
Q

what is the function of the muscularis?

A

to mix & propel contents w/in GI tract

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24
Q

what do contractions of the circular layer and of the longitudinal layer of the muscularis do?

A

circular layer contractions constrict lumen of tube

longitudinal layer contractions shorten tube

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25
Q

what are the 2 primary modes of motility?

A

peristalsis

mixing

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26
Q

what is peristalsis?

A

alternating contraction sequence of inner circular and outer longitudinal muscle layers to propel ingested materials through GI tract

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27
Q

what is mixing?

A

back & forward (kneading) motion - occurs at any point in time w/in different regions - no directional movement.
purpose is to blend ingested materials with secretions w/in GI tract

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28
Q

what is the difference between an adventitia and a serosa?

A

adventitia - composed of areolar CT w/collagen & elastic fibers - found outside peritoneal cavity
serosa - same composition as adventitia AND completely covered by a visceral peritoneum - found w/in peritoneal cavity

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29
Q

How does the stomach differ from typical pattern of tunics?

A

it has 3 layers of smooth muscle in the muscularis

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30
Q

what serous membranes are associated with the abdominal cavity?

A 
parietal peritoneum (serous membrane that lines inside surface of body wall)
visceral peritoneum (serous membrane that reflects over & covers surface of internal organs)
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31
Q

what is the peritoneal cavity?

A

space between parietal peritoneum and visceral peritoneum.

potential space w/small volume of lubricating serous fluid that is secreted by both peritoneal layers

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32
Q

what is the function of serous fluid in the peritoneal cavity?

A

lubricates internal body wall & external organ surfaces
allows organs to move freely
reduces friction resulting from movement

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33
Q

what are intraperitoneal organs?

A

organs within abdomen that are completely surrounded by visceral peritoneum

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34
Q

what are the intraperitoneal organs?

A

stomach
most of small intestine
parts of large intestine

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35
Q

what are retroperitoneal organs?

A

organs where only the anterolateral portions are covered w/peritoneum - typically lie directly against posterior abdomen wall
most of duodenum (1st part of small intestine)
pancreas
ascending and descending colon (parts of large intestine)
rectum

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36
Q

What is mesentery?

A

double-layer of peritoneum that supports, suspends and stabilizes the intraperitoneal GI tract organs.

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37
Q

what is housed in between the folds of the mesentary?

A

blood vessels, lymph vessels, and nerves —> supply the digestive organs

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38
Q

what is the greater omentum?

A

the mesentery that extends inferiorly like an apron from inferolateral surface of stomach
also called fatty apron because it often accumulates lots of adipose tissue. ick

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39
Q

what is the lesser omentum?

A

the mesentery that connects the superomedial surface of the stomach & proximal end of duodenum to liver

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40
Q

what is the falciform ligament?

A

the mesentery that attaches the liver to the internal surface of the anterior abdominal wall

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41
Q

what is the mesentery proper?

A

sometimes referred to as the mesentery
fan-shaped fold of peritoneum that suspends most of the small intestine from the internal surface of the posterior abdominal wall

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42
Q

what is the mesocolon?

A

mesentery that attaches parts of the large intestine to the internal surface of the posterior abdominal wall.
has distinct sections named for portion of colon it suspends
(transverse mesocolon, sigmoid mesocolon…)

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43
Q

List the mesenteries

A 
greater omentum
lesser omentum
falciform ligament
mesentery proper
mesocolon
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44
Q

What are the 2 types of general receptors?

A

mechanoreceptors (detect either stretch or pressure)

chemoreceptors (detect specific chemicals)

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45
Q

where does sensory input from mechanoreceptors and chemoreceptors go?

A

CNS

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46
Q

which nerves convey autonomic motor output to digestive system mechanoreceptors and chemoreceptors?

A

3 cranial nerves
facial
glossopharyngeal
vagus

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47
Q

what are long reflexes?

A

coordinated secretory and smooth muscle contractions involved in digestive responses controlled by autonomic interactions of the central nervous system

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48
Q

what are short reflexes?

A

digestive reflexes that do not involve the CNS. occur only within neurons of enteric nervous system that are housed in GI tract wall.

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49
Q

what are the hormones that participate in the regulation of digestion?

A

gastrin (released from stomach)

secretin and cholecystokinin (released from small intestine)

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50
Q

what structures are considered part of the upper gastrointestinal tract?

A 
oral cavity
salivary glands
pharynx
esophagus
stomach
duadenum (1st part of the small intestine)
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51
Q

what is the function of the oral cavity in digestion?

A

mechanical digestion begins here. salivary glands excrete saliva to mix with food to form wet mass called bolus
saliva contains salivary amylase, a hydrolytic enzyme that initiates digestion of starch (amylose)

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52
Q

what is bolus?

A

wet mass of food plus saliva

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53
Q

what is the function of the pharynx in digestion?

A

where swallowing of the bolus occurs

upper part secretes mucus (as do salivary glands in saliva) to help w/swallowing

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54
Q

what is the function of the esophagus in digestion?

A

secretes mucus to lubricate passage of bolus. Bolus comes here from pharynx and then goes to stomach

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55
Q

what is the function of the stomach in digestion?

A

smooth muscle of stomach wall secrete gastric juice as they contract –> mixes with bolus. secretions are produced by epithelial cells of stomach mucosa. include HCl, digestive enzymes and mucin
forms acidic puree called chyme

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56
Q

what are the regions of the oral cavity?

A

vestibule (buccal cavity) - space b/t gums, lips & cheesk
oral cavity proper - central to the teeth and bound laterally by cheeks, anteriorly by teeth & lips & posteriorly by oropharynx

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57
Q

what are the muscles of the cheeks & what are their function?

A

buccinator muscles

compress cheeks against teeth to hold solid materials in place during mastication

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58
Q

what forms the lips?

A

orbicularis oris muscle

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59
Q

why are lips red?

A

lots of superficial blood vessels & less keratin in outer skin

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60
Q

what are gums?

A

gingivae

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61
Q

how are lips attached to the gums?

A

labial frenulum

thin mucosa fold in the midline of lips

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62
Q

what forms the roof of the oral cavity and what is its function?

A

the palate

separates the oral cavity from the nasal cavity

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63
Q

what is the hard palate?

A

anterior 2/3 of palate

formed by palatine processes of maxillae and horizontal plates of palatine bones

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64
Q

what are the ridges on the hard palate and what is their purpose?

A

transverse palatine folds - friction ridges

assist tongue in manipulating ingested materials prior to swallowing

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65
Q

what is the uvula?

A

extends inferiorly from posterior part of soft palate - conical projection

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66
Q

what prevents food from entering nasal region during swallowing?

A

soft palate and uvula elevate & close off posterior entrance into nasopharynx during swallowing

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67
Q

what are the openings between the oral cavity and the oropharynx?

A

fauces
bound by paired muscular folds
palatoglossal arch (anterior) and
palatopharyngeal arch (posterior)

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68
Q

what is housed in between the palatoglossal arch and the palatopharyngeal arch?

A

palatine tonsils

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69
Q

what is the tongue made out of?

A

skeletal muscle

extrinsic and intrinsic muscles

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70
Q

what are the bumps on the tongue?

A

papillae

involved in sense of taste

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71
Q

what else is on the tongue besides papillae?

A

lingual tonsils - round masses of lymphatic tissue on posteroinferior region

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72
Q

how is the tongue attached to the bottom of the oral cavity?

A

lingual frenulum

thin vertical mucous membrane

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73
Q

what is the histology of the oral cavity?

A

epithelial lining is stratified squamous epithelium - protects against abrasion during mechanical digestion
nonkeratinized except for lips, parts of the tongue & small part of hard palate

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74
Q

what are intrinsic salivary glands?

A

unicellular glands including buccal glands of cheek, lingual glands of tongue & labial glands of lips –> contribute to production of saliva –> secretions include lingual lipase enzyme

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75
Q

where is most saliva produced?

A

multicellular exocrine glands outside of oral cavity called extrinsic salivary glands

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76
Q

What are the pairs of multicellular salivary glands?

A

parotid
submandibular
sublingual

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77
Q

describe the parotid salivary glands

A

largest
located anterior & inferior to ear - partially overlaying masseter muscle
produce about 25-30% of saliva
conducted through parotid duct to oral cavity

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78
Q

how are the parotid glands attached to the oral cavity?

A

through parotid duct - extends from the gland, across the external surface of the masseter muscle, penetrate the buccinator muscle & opens into the vestibule of oral cavity near 2nd molar

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79
Q

describe the submandibular salivary glands

A

inferior to the floor of oral cavity & medial to body of mandible
produce most of saliva - 60-70%
connected to oral cavity through submandibular duct - opens from each gland through a papilla in the floor of the oral cavity on the lateral sides of the lingual frenulum

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80
Q

describe the sublingual salivary glands

A

inferior to tongue, medial and anterior to submandibular salivary glands, internal to oral cavity mucosa
connected by multiple tiny sublingual ducts that open onto inferior surface of oral cavity, posterior to submandibular duct papilla
contribute 3-5% total saliva

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81
Q

what is the histology of paired salivary glands?

A

they have mucous cells and serous cells
mucous cells secrete mucin (forms mucus with water)
serous cells secrete watery fluid containing electrolytes and salivary amylase
also have salivary ducts

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82
Q

what types of secretions do each of the salivary glands produce?

A

parotid - only serous secretions

submandibular and sublingual - both serous and mucus secretions

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83
Q

what is the production rate of saliva?

A

1 - 1.5 L/day

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84
Q

what are the components of saliva?

A

salivary amylase, lingual lipase (from intrinsic salivary glands), mucin, ions (Na+, K+, Cl-, HCO3-), lysozyme (antibacterial), immunoglobulin A (from plasma cells)

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85
Q

what is the pH range of saliva?

A

slightly acidic 6.4-6.8

99.5% water, the rest are solutes

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86
Q

What are the functions of saliva?

A

moistens food & helps it become bolus
initiates chemical breakdown of starch (salivary amylase)
food molecules dissolved in it so taste receptors can be stimulated
cleanses oral cavity structures
helps inhibit bacterial growth b/c it contains lysozyme & IgA

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87
Q

what regulates salivary secretion?

A

salivary nuclei within the brainstem
basic level is maintained by parasympathetic stimulation to make sure oral cavity is moist
input to salivary nuclei received from chemoreceptors or mechanoreceptors in upper GI tract when stimulated by substances in oral cavity (esp. acid), arrival of food in stomach lumen (esp. spicy or acid)
higher brain centers send input in response to though, smell or sight of food
stimulation of salivary nuclei —> increased parasympathetic output relayed along facial nerve to submandibular & sublingual salivary glands & along glossopharyngeal nerve to parotid salivary glands

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88
Q

how does sympathetic stimulation affect salivary secretions?

A

occurs during exercise, excitement or anxiety —> more viscous saliva by decreasing water content because sympathetic stimulation constricts capillaries of salivary glands & so decreases fluid added to saliva

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89
Q

what is mastication?

A

mechanical digestion in the oral cavity

chewing

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90
Q

what controls mastication?

A

coordinated by nuclei within medulla oblongata & pons: the mastication center

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91
Q

what is the primary function of chewing?

A

to reduce bulk of food into smaller particles

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92
Q

does chewing affect digestion & absorption?

A

not much

surface area of food is increased - so that does affect exposure to enzymes

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93
Q

what kinds of medications can be absorbed in the mouth?

A

small, nonpolar molecules that go under the tongue, pass through oral cavity epithelium by diffusion & absorb into blood

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94
Q

what is another word for teeth?

A

dentition

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95
Q

what are the parts of a tooth?

A

crown, neck, root

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96
Q

how are the teeth connected?

A

roots fit into dental alveoli (sockets) in alveolar processes of maxillae and mandible
bound by periodontal ligament to form gomphosis joint

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97
Q

what forms the primary mass of a tooth?

A

dentin - harder than bone

covered by enamel - hardest substance in the body, composed of calcium phosphate crystals

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98
Q

what is in the middle of a tooth?

A

pulp cavity full of pulp (connective tissue)

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99
Q

what is the apical foramen?

A

opening in root of tooth from pulp cavity where blood vessels & nerves connect with body.

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100
Q

what surrounds the root of teeth?

A

cementum

hard material

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101
Q

what are deciduous teeth?

A

baby teeth (milk teeth)

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102
Q

how many deciduous teeth are there & when do they arrive?

A

20 - usually start between 6 -30 months

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103
Q

how many permanent teeth are there?

A

32

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104
Q

name the teeth

A

from middle out
incisors (central and lateral) (slicing & cutting)
canines (puncturing & tearing)
premolars (1st & 2nd) - cusps crush and grind, 1-2 roots
molars (1st, 2nd & 3rd) 3+ roots - grinding & crushing

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105
Q

what are gums?

A

gingivae
composed of dense irregular CT
nonkeratinized stratified squamous epithelium covers alveolar processes of upper & lower jaws & surrounds neck of teeth

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106
Q

what forms the walls of the pharynx?

A

3 skeletal muscle pairs

superior, middle & inferior pharyngeal constrictors

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107
Q

what lines the walls of the pharynx?

A

oropharynx & laryngopharynx are lined with nonkeratinized stratified squamous epithelium - protection against abrasion

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108
Q

describe the esophagus

A

normally collapsed
10 inches long in adult
begins at level of cricoid cartilage of larynx
anterior to vertebral bodies until it goes through diaphragm through esphageal hiatus & connects to stomach

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109
Q

describe the sphincters of the esophagus

A

superior esophageal sphincter (pharyngoesophageal): circular skeletal muscle ring where esophagus & pharynx meet - closes during inhalation
inferior esophageal sphincter (esophageal gastric or cardiac sphincter): ring of circular smooth muscle - not strong enough to prevent backflow so diaphragm muscles contract to help

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110
Q

what lines the mucosa of the esophagus?

A

nonkeratinized stratified squamous epithelium

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111
Q

describe the submucosa of the esophagus

A

thick
lots of elastic fibers so it can stretch during swallowing
lots of mucous glands that provide thick mucus for epithelium (lubrication) - ducts project through mucosa & open into lumen

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112
Q

describe the muscularis of esophagus

A

has both skeletal & smooth muscles
2 layers in top third are skeletal (not smooth), because skeletal contracts more quickly than smooth so food can get down before next inhalation
middle third has both
bottom third has just smooth - beginning of continuous smooth muscle muscularis that goes through stomach, small & large intestines, to anus

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113
Q

what is the outer most layer of the esophagus?

A

adventitia

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114
Q

what is another name for swallowing?

A

deglutition

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115
Q

what are the 3 phases of swallowing?

A

voluntary
pharyngeal
esophageal

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116
Q

describe the voluntary phase of swallowing

A

controlled by cerebral cortex

bolus is pushed by tongue against hard palate & moves toward oropharynx

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117
Q

describe the pharyngeal phase of swallowing

A

involuntary
initiated by arrival of bolus at entryway to oropharynx
stimulates sensory receptors around fauces. nerve signals relayed to effectors to cause: entry of bolus into oropharynx, elevation of soft palate & uvula to block passageway b/t oropharynx & nasopharynx, elevation of larynx by hyoid muscles in neck to move epiglottis to cover laryngeal opening (so food doesn’t go into larynx & trachea), inhibition of respiratory center in medulla oblongata so that breath isn’t taken during swallowing

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118
Q

how long is the pharyngeal phase of swallowing?

A

about 1 second as pharyngeal constrictors contract from top to bottom, creating pressure difference & forcing food down into esophagus

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119
Q

describe the esophageal phase of swallowing

A

involuntary
bolus goes from esophagus into stomach - 5-8 seconds
presence of bolus in lumen of esophagus stimulates sequential peristaltic waves of muscular contraction
pressure difference moves bolus down

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120
Q

when do superior & inferior esophageal sphincters open & close?

A

closed at rest
relax when bolus is swallowed
after bolus passes inferior esophageal sphincter, nerve signals cause it to contract

121
Q

what kind of digestion occurs in the stomach?

A

mechanical and chemical

chemical digestion of protein & fat begin here

122
Q

how many liters of stuff enter stomach each day?

A

3-4 liters of food, drink & saliva

123
Q

how long does stuff stay in the stomach?

A

between 2-6 hours

fatty stuff takes longest to empty

124
Q

what kinds of things absorb in the stomach?

A

small nonpolar substances that come in contact with mucosa

alcohol & aspirin

125
Q

what are the regions of the stomach?

A

greater & lesser curvature
cardia (entryway into stomach lumen from esophagus)
cardiac orifice - internal opening where cardia meets esophagus
fundus - top of the stomach above esophageal opening
body - main part
pylorus - funnel shaped pouch at the end of the stomach
pyloric orifice - opening of pylorus into duodenum
pyloric sphincter - thick ring of circular smooth muscle around pyloric orifice

126
Q

what does the pyloric sphincter do?

A

regulates entry of material into small intestine

127
Q

what is the gross anatomy of the inside of the stomach

A

full of gastric folds or rugae

128
Q

what is the purpose of the gastric folds?

A

allow it to expand greatly when full of food

129
Q

what membranes are associated with the stomach?

A

greater and lesser omentum
greater omentum extends inferiorly from greater curvature of stomach forming fatty apron that covers anterior surface of abdominal organs
lesser omentum extends superiorly from the lesser curvature of stomach & duodenum to liver

130
Q

describe the histology of the stomach

A

thin mucosa 1.5mm at thickest - lined by simple columnar epithelium supported by lamina propia, indented by gastric pits
gastric glands extend deep into mucosa from base of each gastric pit - surrounded by muscularis mucosa that helps expel gastric gland secretions
muscularis had 3 smooth muscle layers (rather than 2 in rest of GI tract), inner oblique, middle circular, outer longitudinal. gets thicker as it goes from body to pyloris
serosa is outer layer - visceral peritoneum (stomach is intraperitoneal)

131
Q

what is the purpose of the 3 layers of muscularis in the stomach?

A

churning and blending of bolus to help mechanically digest food

132
Q

What are the types of secretory cells of the gastric epithelium?

A 
surface mucous cells
mucous neck cells
parietal cells
chief cells
G-cells
133
Q

describe surface mucous cells

A

line the stomach lumen & extend into gastric pits
secrete alkaline product that contains mucin onto gastric surface
mucin + water makes 1-3mm thick mucus layer - helps prevent ulceration of stomach lining w/high acidity of gastric fluid & gastric enzymes

134
Q

how much gastric juice is produced a day?

A

3L

135
Q

describe mucous neck cells

A

located immediately deep to the base of the gastric pit & interspersed among parietal cells
produce acidic mucin - helps maintain acidic conditions - lubricating properties to help protect lining from abrasion & mechanical injury

136
Q

describe parietal cells

A

also called oxyntic cells
add intrinsic factor - a glycoprotein - only essential function performed by stomach. required for absorption of B12 in ileum - B12 is necessary for erythrocyte production
adds HCl - forms from H+ and Cl- secreted across parietal cell’s surface - creates low pH in stomach

137
Q

what is the function of HCl in the stomach?

A

converts inactive enzyme pepsinogen into active pepsin & provides optimal pH for pepsin activity
kills most microorganisms
contributes to breakdown of plant cell walls & animal CT
denatures proteins - facilitating chemical digestion by enzymes

138
Q

describe chief cells

A

also called zymogenic cells or peptic cells
most numerous secretory cells w/in gastric glands
produce & secrete packets of zymogen granules primarily containing pepsinogen (inactive form of proteolytic enzyme pepsin) - has to be produced inactive form to prevent destruction of chief cell proteins
produce gastric lipase - small role in fat digestion (about 10-15% of fats)

139
Q

what happens to pepsinogen in the stomach?

A

activated by HCl and other active pepsin molecules

chemically digests denatured proteins into smaller peptide fragments (oligopeptides)

140
Q

describe G-cells

A

enteroendocrine cells
widely distributed in gastric glands
secrete gastrin hormone into blood

141
Q

what does gastrin do?

A

a hormone that stimulates stomach secretions and motility

142
Q

what is a peptic ulcer?

A

chronic, solitary erosion of a portion of the lining of either the stomach or the duodenum
gastric ulcers are in the stomach
duodenal ulcers are in the superior part of the duodenum

143
Q

what is the purpose of smooth muscle activity in the stomach?

A

mixing bolus with gastric juice to form chyme

emptying chyme from stomach into small intestine

144
Q

describe steps of gastric mixing & emptying

A
  1. contractions of smooth muscle mix bolus with gastric secretions to form chyme
  2. peristaltic wave results in pressure gradient that moves stomach contents toward pylorus sphincter
  3. pressure gradient increases force in pylorus against pyloric sphincter
  4. pyloric sphincter opens, small amount of chyme enters duodenum (3mL)
  5. pyloric sphincter closes & retropulsion occurs
145
Q

what is retropulsion?

A

when pyloric sphincter closes, stomach contents are squeezed back toward stomach body –> additional mixing of contents to further reduce size of food particles

146
Q

how are the digestive processes in the stomach regulated?

A

pacemaker cells in stomach wall spontaneously depolarize less than 4X/min. - establishes rhythm of muscular contraction
electrical signals spread via gap junctions
regulated by both nervous reflexes and hormones, which alter force but not rate of contractions (constant)
secretory of gastric glands is also altered
3 phases

147
Q

what are the 3 phases of digestion?

A

cephalic phase
gastric phase
intestinal phase

148
Q

describe the cephalic phase of digestion

A

involves the cephalic reflex initiated by thought, smell, sight or taste of food
nerve signals from higher regions of brain are sent to hypothalamus –> relays nerve signals to medulla oblongata —> increases vagal stimulation of stomach by increasing parasympathetic output along vagus nerve to stomach, —> increase in contractile force in gastric wall (increasing motility) & secretory activity of gastric glands (stomach growling)

149
Q

describe the gastric phase of digestion

A

happens when bolus reaches stomach
regulated by nervous system via gastric reflex and endocrine system by release of gastrin hormone
gastric reflex initiated as food enters stomach - baroreceptors in stomach wall detect stretch, chemoreceptors detect protein and increase in pH of gastric contents. nerve signals relayed to medulla oblongata resulting in same effect as cephalic reflex - increase in stomach motility & secretory activity

150
Q

during gastric phase, what hormone does the presence of food stimulate?

A

release of gastrin from enteroendocrine cells
gastrin enters blood & circulates back to stomach to stimulate contractile activity & increase HCl release from parietal cells
also stimulates contraction of pyloric sphincter to slow stomach emptying giving enough time for digestive activities w/in stomach

151
Q

describe the intestinal phase of the stomach

A

processes following chyme reaching small intestine
regulated by nervous system and endocrine system
involves intestinal reflex & release of 2 hormones: cholecystokinin (CCK) and secretin

152
Q

how are the intestinal reflex, gastric reflex & cephalic reflex related?

A

intestinal reflex opposes other 2 reflexes

153
Q

what is the function of the intestinal reflex?

A

protects small intestine from being overloaded with chyme
initiated w/entry of acidic chyme into duodenum –> initiates inhibitory nerve signals to medulla oblongata –> vagal stimulation to stomach is decreased —> decrease in motility & secretory activity of the stomach

154
Q

what do cholecystokinin & secretin do?

A

decrease stomach motility & secretory activity
inhibit release of gastrin
slows down emptying of stomach

155
Q

what comprises the lower GI tract?

A 
small intestine (duodenum, jejunum, ileum - duodenum is considered part of upper GI tract)
accessory organs
large intestine
156
Q

what is the purpose of accessory organs in the lower GI tract?

A

they secrete bile & pancreatic juice. Bile is produced by liver, stored concentrated & released by gallbladder. pancreatic juice has numerous digestive enzymes produced & released by pancreas.

157
Q

how much stuff enters the small intestine?

A

9-10 L of food, water & digestive system secretions / day

158
Q

how long does stuff spend in the small intestine?

A

at least 12 hours

159
Q

what is the function of the small intestine?

A

finishes chemical digestion process, absorbes most of the nutrients & a large percentage of water & electrolytes
absorbs vitamins

160
Q

how long is the small intestine?

A

6 meters on cadaver - shorter in living person due to muscle tone

161
Q

Describe the duodenum

A

duodenum - 1st segment, 10” long C-shape around pancreas & meets jejunum @ duodenojejunal flexure
most is retroperitoneal, proximal part is intraperitoneal & connected to liver by lesser omentum
receives accessory gland secretions from liver, gallbladder & pancreas

162
Q

what are the sections of the small intestine?

A

duodenum
jejunum
ileum

163
Q

describe the jejunum

A

middle region
7.5 feet - 2/5 of total length of small intestine
primary region for chemical digestion & nutrient absorption
intraperitoneal & suspended in abdomen by mesentery

164
Q

describe the ileum

A

last region of small intestine
10.8’ long
3/5 of small intestine
distal end terminates at ileocecal valve - sphincter that controls entry of material into large intestine
intraperitoneal & suspended in abdomen by mesentery
absorption of digested material continues in ileum

165
Q

describe the mucosal & submucosal tunics on the small intestines

A 
internal circular folds called plicae
increase surface area for nutrient absorption
speed bumps to slow down chyme
most numerous in duodenum & jejunum
least numerous in ileum
166
Q

describe the histology of the small intestine

A

length of muscularis mucosae is shorter than two layers internal to it —> makes villi - larger & more numerous in jejunum
epithelium is glove covering the lamina propria finger
villus has arteriole, capillary network (absorbs most nutrients), venule, lacteal (absorbs lipids & lipid-soluble vitamins too large to be absorbed by blood capillaries)
microvilli - extensions of plasma membrane on simple columnar epithelial cells lining small intestine - look fuzzy so called brush border

167
Q

what is in the brush border?

A

enzymes that complete chemical digestion - called brush border enzymes
also embedded w/in membrane are required proteins for transport of digestion products

168
Q

where are intestinal glands located and what is their purpose?

A

between intestinal villi - invaginations of mucosa
also called intestinal crypts
mucosal cells that secrete intestinal juice
extend to base of mucosa (slightly resemble gastric glands of stomach)

169
Q

what are the types of intestinal glands?

A

goblet cells - produce mucin that forms mucus with water - lubricates & protects intestinal lining - increase in number from duodenum to ileum because more lubrication needed as nutrients are absorbed & undigested stuff left behind
unicellular gland cells - synthesize enteropeptidase
enteroendocrine cells - release hormones like CCK and GIP

170
Q

what kind of gland is housed in the submucosa only in the proximal duodenum?

A

submucosal or duodenal gland (Brunner gland)

produces viscous, alkaline mucus that protects duodenum from acidic chyme

171
Q

what are the functions of smooth muscles in small intestine?

A

mixing chyme with accessory gland secretions
moving chyme continually against new areas of brush border
propelling contents through small intestine toward large intestine

172
Q

what are the two types of muscle processes in the small intestine?

A

segmentation & peristalsis
segmentation (more prevalent at entry of small intestine) mixes chyme with accessory gland secretion through back & forth motion
peristalsis propels material w/in lumen by alternating contraction of circular and longitudinal muscle layers in small regions - rhythm of contractions is more frequent in duodenum than ileum so net movement of intestinal contents is toward the large intestine

173
Q

what is the gastroileal reflex?

A

moves contents from ileum to cecum in response to food entering stomach
ileocecal sphincter usually is constricted, but activity in ileum during digestion makes it relax to allow small intestine contents to enter large intestine
contraction of sphincter closes passage to decrease backflow into ileum

174
Q

What are the accessory organs associated with the duodenum?

A

liver
gallbladder
pancreas

175
Q

what delivers secretions of accessory organs to duodenum?

A

biliary apparatus
network of thin ducts:
right & left hepatic duct drain left & right lobes of liver –> merge to form common hepatic duct –> merges with cystic duct (from the gallbladder) to form common bile duct that extends inferiorly to duodenum

176
Q

what is the hepatopancreatic ampulla?

A

swelling on posterior duodenal wall where common bile duct and main pancreatic duct merge & pierce duodenal wall

177
Q

what is the area called where common bile duct & main pancreatic duct merge & enter duodenum?

A

hepatopancreatic ampulla

178
Q

what does the hepatopancreatic sphincter do?

A

regulates movement of bile & pancreatic juice into duodenum

179
Q

what is the projection called within the duodenum where the bile & pancreatic juice enter through the ducts

A

major duodenal papilla

180
Q

what is an alternative way for small amounts of pancreatic juice to enter duodenom?

A

accessory pancreatic duct - penetrates duodenal wall & forms the minor duodenal papilla

181
Q

what is the liver’s main function in digestion?

A

production of bile

182
Q

what is the gross anatomy of the liver?

A

covered by CT capsule & layer of visceral peritoneum (except for small region on diaphragmatic surface called bare area)
4 partially separated lobes, supported by 2 ligaments right & left lobe (right is bigger - separated from left by falciform ligament, a peritoneal fold that holds liver to anterior abdomen wall)
caudate lobe & quadrate lobes are within the right lobe
caudate is adjacent to inferior vena cava
quadrate lobe is adjacent to gall bladder

183
Q

how is blood supplied to the liver?

A

dual supply - 1 oxygenated, 1 deoxygenated
hepatic artery is branch of celiac trunk that carries oxygenated blood to liver
hepatic portal vein is part of hepatic portal system - carries blood from capillary beds of GI tract, spleen & pancreas - brings 75% of blood volume to liver - rich in nutrients but poor in O2
blood mixes as it passes into & through hepatic lobules

184
Q

what are the structural & functional units of the liver?

A

hepatic lobules
formed by CT capsule that branches throughout the organ forming septa that partition it into thousands of small polyhedral lobules

185
Q

what are liver cells called?

A

hepatocytes

186
Q

what is a portal triad and where is it?

A

at periphery of liver lobule

composed of hepatic duct bile ductule and branches of hepatic portal vein & hepatic artery

187
Q

what is in the middle of each liver lobule?

A

central vein - drains blood flow from lobule

merge throughout liver to form hepatic veins that eventually empty into the inferior vena cava

188
Q

what are hepatic sinusoids?

A

thin-walled capillaries w/large gaps b/t cells - more permeable than other capillaries
venous blood of hepatic portal system & arterial blood mix w/in sinusoids & flow slowly toward central vein
nutrients absorbed from sinusoids into hepatocytes
sinusoids also lined with reticuloendothelial cells (Kupffer cells) - star-shaped - macrophages that eat harmful substances from blood

189
Q

what is between each cord of hepatocytes in the liver lobules?

A

bile canaliculus

channel that conducts bile that is produced by hepatocytes to hepatic duct in portal triad

190
Q

what is bile?

A

alkaline fluid that contains mostly water, bicarbonate ions, bile salts (formed from cholesterol), bile pigments, cholesterol, lecithin (a phospholipid) and mucin
produced by liver
.5-1 L/day

191
Q

what is the function of bile salts & lecithin?

A

function in mechanical digestion of lipids, making more efficient chemical digestion of triglycerides

192
Q

where is the gallbladder?

A

attached to inferior surface of liver

193
Q

what is the function of the gallbladder?

A

stores, concentrates & releases bile that liver produces

194
Q

what is the structure of the gallbladder?

A

3 tunics: inner mucosa, middle muscularis, external serosa

mucosa is folded to permit distension of wall as it fills with bile

195
Q

what connects the gallbladder to the common bile duct?

A

cystic duct

196
Q

what is at the neck of the gallbladder?

A

sphincter valve that controls flow of bile into & out of gallbladder
bile enters when hepatopancreatic sphincter closes & bile backs up through common bile duct & cystic duct into gallbladder.
can hold 40-60mL of concentrated bile

197
Q

what kinds of functions does the pancreas have?

A

endocrine & exocrine

198
Q

what are the endocrine functions of the pancreas?

A

producing & secreting hormones like insulin & glucagon

199
Q

what are exocrine cells of the pancreas called? and what do they do?

A

acinar cells

produce pancreatic juice to assist with digestive activities

200
Q

describe the gross anatomy of the pancreas

A

retroperitoneal
touches the spleen
has a wide head adjacent to curvature of duodenum
body projects toward left lateral abdominal wall
tail tapers as it approaches the spleen

201
Q

what is the histology of the pancreas?

A

modified simple cuboidal epithelial cells (acinar cells) arranged in saclike acini which are organized into large clusters - lobules

202
Q

what do acinar cells of the pancreas do?

A

produce & release hydrolytic enzymes
small ducts lead from each acinus to larger ducts—> to pancreatic ducts —> to duodenum
pancreatic ducts are lined by simple cuboidal epithelial cells & secrete alkaline HCO3- fluid

203
Q

what is pancreatic juice & what cells produce it?

A

acinar cells & cells that line the pancreatic ducts produce it
alkaline fluid most water, HCO3- & hydrolytic enzymes:
pancreatic amylase (digest starch)
pancreatic lipase (digest fats)
inactive proteases (trypsinogen, chymotrypsinogen, procarboxypeptidase) that digest protein when activated
nucleases (digest nucleic acids - DNA RNA)

204
Q

what activates the pancreas to release pancreatic juice?

A

vagal stimulation during cephalic & gastric phase

205
Q

what does CCK do?

A

cholecystokinin
hormone released from small intestine - mostly in response to fatty chyme
stimulates smooth muscle of gallbladder to contract –> releasing concentrated bile
stimulates pancreas to release pancreatic juice
relaxes smooth muscle w/in hepatopancreatic ampulla so bile & pancreatic juice can enter small intestine
inhibits stomach motility & release of gastric secretions

206
Q

what does secretin do?

A

released from small intestine in response to chyme acidity
causes release of alkaline solution that contains HCO3- form liver & ducts of pancreas - helps neutralize acidic chyme
inhibits gastric secretions & motility

207
Q

list the hormones that control digestion

A

gastrin
cholecystokinin
secretin

208
Q

what secrets the digestion hormones?

A

gastrin - G cells in stomach
CCK - enteroendocrine cells of small intestine
secretin - enteroendocrine cells of small intestine

209
Q

what is the stimulus for release of each of the digestion hormones?

A

gastrin - bolus in stomach - especially if it has proteins
CCK - chyme w/amino acids & fatty acids entering small intestine
secretin - acidic chyme entering small intestine

210
Q

what are the targets & effects of the digestion hormones?

A

gastrin: parietal cells: stimulates secretion of HCl - chief cells: stimulates secretion of pepsinogen - pyloric sphincter: stimulates contraction
CCK: stomach: inhibits motility & gastric secretion - gallbladder: stimulates release of bile - pancreas - stimulates release of pancreatic juice - hepatopancreatic sphincter: causes relaxation
secretin: stomach: inhibits gastric secretion & motility - pancreas: stimulates secretion of alkaline solution from pancreatic ducts - liver: stimulates secretion of alkaline solution

211
Q

how much material enters large intestine daily?

A

about 1 L

212
Q

what does the large intestine absorb?

A

water, electrolytes (mostly Na+ and Cl-)

only 100mL water that enters large intestine is lost in feces daily

213
Q

describe the anatomy of the large intestine

A

2.5” diameter, 5’ long
originates at ileocecal junction, terminates at anus
3 regions: cecum, colon and rectum

214
Q

what is the cecum

A

1st portion of the large intestine
right lower abdominal quadrant
extends inferiorly from ileocecal valve
vermiform appendix pokes down - lined w/lymphocyte-filled lymphatic nodules
cecum & appendix are intraperitoneal organs

215
Q

where does chyme enter the large intestine?

A

from the ileum into the ileocecal valve

216
Q

describe the colon

A

begins at level of ileocecal valve - forms the U-shape of large intestine
partitioned into 4 segments:
ascending colon - retroperitoneal b/c posterior wall adheres to posterior abdominal wall
transverse colon - intraperitoneal
descending colon - retroperitoneal
sigmoid colon - intraperitoneal

217
Q

what are the bends in the colon called?

A

right colic flexure (hepatic flexure) from ascending colon to transverse colon (as it approaches anterior surface of liver)
left colic flexure (splenic flexure) from transverse to descending as it approaches spleen in upper left quadrant of abdomen
sigmoid flexure where sigmoid originates - bend at bottom of descending

218
Q

describe the rectum

A

retroperitoneal
rectal valves - thick transverse folds hold poo in while passing gas
anal canal - last few centimeters of large intestine - lined by stratified squamous epithelium - terminates at anus - thing longitudinal ridges called anal columns in between are anal sinuses that release mucin during pressure from poo
at bottom are internal anal sphincter (involuntary smooth muscle) and external anal sphincter (voluntary skeletal muscle)

219
Q

what features are unique to the large intestine?

A 
teniae coli - thin, longitudinal bundles of smooth muscle that act like elastic in a waistband
haustra - many sacs - the teniae coli bunch the large intestine into these sacs
epiploic appendages (omental appendages) - fat lobules that hang off external surface of haustra. gross
220
Q

what is the histology of the large intestine?

A

lined by simple columnar epithelium w/many goblet cells
mucosa is smooth - no villi but does have intestinal glands (crypts) that extend inward toward muscularis mucosae
glands secrete mucin
lots of lymphatic nodules & lymphatic cells are in lamina propia
muscularis of cecum & colon has 2 layers of smooth muscle, but outer longitudinal don’t surround all the way - they form the teniae coli

221
Q

what are the normal bacterial flori of the large intestine called?

A

indigenous microbiota

222
Q

what do normal bacterial flori do in large intestine?

A

chemical breakdown of complex carbohydrates, proteins & lipids that are still in chyme
bacterial action produces CO2, H+, methane etc - partly accounting for smelly poo
also produce B vitamins, vitamin K which is absorbed from large intestine into blood (also absorbed in small intestine from food we eat)

223
Q

what types of movement happen in the large intestine?

A

peristaltic movements: weak & sluggish but resemble small intestine peristaltic movement
haustral churning: happens after relaxed haustrum fills with stuff - distention stimulates reflex contractions in muscularis - increase churning & move material to more distal haustra
mass movement: powerful peristaltic-like contractions involving teniae coli - propel fecal material toward rectum. contraction wave begins in middle of transverse colon - forcing stuff into descending colon, sigmoid colon, & rectum
usually happens 2-3 times a day

224
Q

what reflexes are associated with motility in large intestine?

A

gastrocolic reflex - initiated by stomach distension to cause mass movement
defecation reflex - filling of rectum initiates urge to poo - stimulus results in transmission of nerve signals from receptors to spinal cord, parasympathetic output increases to sigmoid colon & rectum & decreases to internal anal sphincter

225
Q

what does essential nutrients mean?

A

stuff we need to eat to survive

226
Q

what are the essential nutrients?

A 
carbohydrates
lipids
proteins
minerals
vitamins 
water
227
Q

how are carbohydrates classified?

A

monosaccharides (glucose, fructose, galactose)
disaccharides (sucrose, maltose, lactose)
polysaccharides (starch, cellulose)

228
Q

what does chemical digestion of carbohydrates consist of?

A

1) breakdown of starch into individual glucose molecules
2) breakdown of disaccharides into individual monosaccharides that compose them
oral cavity & small intestines main sites

229
Q

where does the digestion of starch begin?

A

oral cavity - catalyzed by salivary amylase –> breaks down chemical bonds between glucose molecules
salivary amylase is inactivated by low stomach pH - usually w/in 15-20 minutes after bolus enters stomach

230
Q

how are carbohydrates broken down in small intestine?

A

(no new enzymes for carbohydrate digestion enter stomach)
pancreatic amylase - synthesized & released by pancreas - digests starch into shorter strands of glucose
brushborder enzymes complete the breakdown of starch: dextrinase & glucoamylase and maltase
lactase (lactose to glucose & galactose), sucrase (sucrose to glucose & fructose)
glucose fructose & galactose are absorbed across small intestinal epithelial lining into blood –> hepatic portal vein to liver –> converted to glucose
cellulose is not digested - facilitates movemetn along GI tract

231
Q

what are proteins?

A

amino acid subunits linked by peptide bonds

232
Q

what does digestion do to proteins?

A

releases individual amino acids so body can use them to build its own proteins

233
Q

how do enzymes work on proteins?

A

either break peptide bonds between specific adjacent amino acids or release amino acids from either end of a protein
all are released as inactive enzymes so that they won’t destroy the proteins within the cells that produce them

234
Q

describe protein breakdown in the stomach

A

begins with pepsin - formed from pepsinogen that is released by chief cells
HCl (released from parietal cells) causes low stomach pH that activates pepsinogen to pepsin, denatures protein to make breakdown easier

235
Q

describe protein breakdown in small intestines

A

pepsin inhibited by high pH
pancreas releases inactive trypsinogen, chymotrypsinogen & procarboxypeptidase into small intestine
enzyme enteropeptidase (synthesized and released by small intestine) activates trypsinogen to trypsin. trypsin activates other trypsinogen & activates chymotrypsinogen to chymotrypsin & procarboxypeptidase to carboxypeptidase
trypsin & chymotrypsin break specific bonds, carboxypeptidase frees amino acid at end
brush border enzyme dipeptidase breaks final bond between dipeptide
aminopeptidase frees amino acids from amino end of protein
amino acids absorbd across small intestine epithelial lining & enter blood

236
Q

what are lipids?

A

not water-soluble
triglycerides (glycerol molecule & 3 fatty acids - enzymes need t break bonds between glycerol & fatty acids) & cholesterol (doesn’t have to be digested to be absorbed)

237
Q

describe lipid digestion in stomach

A

lingual lipase is component of saliva in oral cavity - not activated until it reaches stomach
in stomach lingual lipase & gastric lipase (produced by chief cells) digest some triglycerides 30% to diglyceride & fatty acid. don’t need bile salts

238
Q

describe lipid digestion in small intestine

A

pancreatic lipase (released in duodenum) digests triglyceride into monoglyceride & 2 free fatty acids
emulsification (action of bile salts) separates big lipid droplets so that lipase can digest - make micelles
last portion of ileum, bile salts are recovered by active transport & recycled to liver for reuse
new bile salts synthesized by hepatocytes

239
Q

describe bile salts

A

amphipathic molecules - polar head & nonpolar tail
nonpolar tails surround fat & make micelle
no brushborder enzymes required for breakdown of triglycerides

240
Q

describe lipid absorption

A

micelles transport lipids to simple columnar epithelial lining of small intestine
enter epithelial cells (ball salts remain)
inside epithelial cells, fatty acids are reattached to monoglyceride to re-form triglycerides
triglycerides, cholesterol & other lipid molecules wrapped with protein to form chylomicron - released by exocytosis –> enter lacteals (too big to enter blood capillaries)

241
Q

describe nucleic acid breakdown in small intestine

A

nucleases synthesized & released by pancreas start digestion of nucleic acid
brush border enzymes (phosphatase breaks phosphate bond and nucleosidase breaks bond b/t sugar & N base)
all components are absorbed across epithelium of small intestine to blood: phosphate, sugar, nitrogenous bases

242
Q

how much water is required daily by the body?

A

2-3L

243
Q

what are the nutrient biomolecules?

A

carbohydrates, lipids & proteins

nucleic acid not considered nutrients because they aren’t required in our diet for survival

244
Q

what are carbohydrates?

A

simple sugar monomers (monosaccharides), disaccharides, and polysaccharides

245
Q

what is the function of carbohydrates?

A

glucose –> broken down to generate energy for life processes
glycogen (polymer of glucose molecules) stored in liver & skeletal muscle tissue

246
Q

what is the function of lipids?

A

triglycerides store energy
phospholipids compose cell membranes
steroids are components of plasma membranes, serve as hormones & precursors for synthesis of bile salts
eicosanoids are local hormones

247
Q

what is the function of proteins?

A

structural & functional components of the body

248
Q

what is the function of vitamins?

A 
coenzymes in chemical reactions
participate in CT synthesis
part of visual pigment in eye
enhance Ca absorption
aid in bone formation
249
Q

what is the function of minerals?

A

required in bone formation, nerve & muscle formation

component of nucleic acids, ATP and part of hemoglobin

250
Q

what is the function of water?

A

support life - cohesion, adhesion, surface tension, high specific heat, high heat of vaporization

251
Q

what are proteins?

A

formed by 20 different amino acids & contain nitrogen in the amine group
nonessential amino acids can be made in the body
8 essential amino acids must come from food
can be categorized as complete (supply all essential amino acids) or incomplete (do not supply all essential amino acids)

252
Q

what are the fat soluble vitamins?

A

K - leafy green vegetables - clotting
A - liver, milk products, green vegetables - eyes
D - cod liver oil, dairy products, UV rays - Ca absorption
E - leafy greens, seeds, butter - cell membrane & fatty acid protection from oxidation

253
Q

how are fat soluble vitamins absorbed in body?

A

w/in lipid micelles - enter lacteals

excess is stored w/in body fat & can be toxic

254
Q

name the minerals required by humans

A

Major: CaClCo MgMnP KNaS
Minor: CrCuF IFe SeZn

255
Q

what is the function of iron?

A

present in hemoglobin w/in erythrocytes (binds O2) & w/in mitochondria in e- transport system (binds e-‘s)

256
Q

what is the function of calcium?

A

required for formation & maintenance of skeleton, blood clotting, exocytosis of neurotransmitters

257
Q

what is the function of sodium & potassium?

A

maintain resting membrane potential in excitable cells

required to generate Action Potential

258
Q

what is the function of iodine?

A

needed to produce thyroid hormone

259
Q

what is the function of zinc?

A

roles in protein synthesis & wound healing

260
Q

how do we get minerals?

A

from food

261
Q

what is the difference between major minerals & minor minerals

A

major minerals - we need more than 100mg/day

minor (trace) - we need less

262
Q

what are sources of carbohydrates?

A

starch (potatoes breads rice grains)
lactose (milk)
sucrose (sugar, maple syrup, fruits)
disaccharides (maltose in cereal), monosaccharides (fructose & glucose), high fructose corn syrup

263
Q

what is our source of lipids?

A

fats & oils
cholesterol (component of all animal-based products b/c it is wi/in plasma membrane of animal cells) - also synthesized by liver

264
Q

what is our source of protein

A

meat, dairy, beans nuts

also supply nitrogen - needed for N- bases of DNA & RNA

265
Q

what is nitrogen balance?

A

equilibrium b/t dietary intake & loss in urine & feces
positive N balance when we absorb more N than excrete (when growing, pregnant or recovering from injury)
negative N balance - more N excreted than absorbed (malnutrition or blood loss)

266
Q

what affects how much of each nutrient you need?

A

age, sex, body mass, level of physical activity, health, pregnancy

267
Q

how is my plate divided?

A

half is fruits & vegetables
half is proteins & grains
milk is a cup on the side

268
Q

what is the absorptive state?

A

time you are eating, digesting & absorbing nutrients
lasts about 4 hours after meal
concentrations of glucose, triglycerides & amino acids are increasing in blood as they are absorbed from GI tract

269
Q

what is the ideal blood glucose level?

A

70-110mg/dL

270
Q

what hormone is released during absorptive state?

A

insulin

271
Q

what does insulin do to regulate blood nutrient levels?

A

stimulates liver cells & muscle cells to form glycogen from glucose (glycogenesis)
causes adipose connective tissue to increase uptake of triglycerides from blood, stimulates lipogenesis & inhibits lipolysis
stimulates most cells to increase amino acid uptake –> accelerated rate in protein synthesis
decrease in all energy-releasing molecules in blood, increase in storage of glycogen & triglycerides & formation of protein w/in body tissues

272
Q

what is the postabsorptive state?

A

time between meals when body relies on stores of nutrients b/c no absorption of nutrients is happening

273
Q

what is the major regulating hormone during the postabsorptive state?

A

glucagon

274
Q

what effects does glucagon have?

A

stimulates liver cells to catabolize glycogen to glucose - increase glycogenolysis and gluconeogenesis (formation of glucose from noncarbohydrate sources)
causes adipose CT to break down triglycerides to glycerol & fatty acids by stimulating lipolysis
glucose released from liver, fatty acids released from fat storage
glucagon has no effect on body proteins because there is no storage of amino acids or proteins in cells

275
Q

what is the functional unit of the liver?

A

liver lobule
microscopic
composed of cords of hepatocytes that radiate out from a central vein
sinusoids are located between cords (capillaries)
oxygenated blood from hepatic artery & deoxygenated (nutrient-rich) blood from hepatic portal vein travel through liver sinusoids toward central vein
bile canaliculi are b/t each cord of hepatocyte & get bile synthesized by hepatocyte - bile drains eventually to small intestine

276
Q

describe cholesterol synthesis

A

fatty acids go from blood to sinusoid to hepatocyte
broken down into 2 C units to form acetyl CoA through beta oxidation process
Acetyl CoA molecules are used to synthesize cholesterol in enzymatic pathway using enzyme called HMG-CoA reductase
basal level of cholesterol production adjusts according to intake

277
Q

what happens to cholesterol after it is synthesized?

A

1) released into blood as component of very-low-density lipoproteins (VLDLs) OR
2) synthesized into bile salts & released as part of bile into small intestine -10% bile salts go out w/poo - way of eliminating excess cholesterol & lowering blood cholesterol levels

278
Q

how are lipids transported in blood?

A

lipids are hydrophobic, so they are wrapped in water-soluble protein –> lipoprotein - contain triglycerides, cholesterol & phospholipids inside protein wrapper

279
Q

what is a chylomicron?

A

triglycerides & some cholesterol wrapped in protein - formed in epithelial cells lining small intestine so that they can be absorbed into a lacteal & transported w/in lymph until it enters venous blood at junction of jugular & subclavian vein

280
Q

what are the 3 categories of lipoproteins formed in the liver?

A

1) very-low-density lipoproteins (VLDL) - contain the most lipid
2) low-density lipoproteins (LDL) somewhat less lipid
3) high-density lipoproteins - least amount of lipid
all 3 transport lipids between liver & peripheral tissues

281
Q

which lipoproteins transport lipids from liver to peripheral tissues?

A

VLDLs - mostly deliver lipids to adipose CT - after delivery become LDL
LDLs - have high amounts of cholesterol - deliver cholesterol to cells. bind to LDL receptors & are engulfed into cell where cholesterol is used in plasma membrane or by certain tissues

282
Q

which lipoproteins transport lipids from tissues to liver?

A

HDLs
proteins are formed in liver & released into blood w/out additional lipid
circulate in blood & fill w/lipids from peripheral tissues & inner lining of arterial walls. transport lipids to liver
excess cholesterol is converted to bile salts w/in liver
HDL’s also make cholesterol available to steroid-producing tissues (like LDL’s) but HDLs are not engulfed by cell when cholesterol is removed.

283
Q

which are the good cholesterols?

A

HDLs because they remove cholesterol from arterial walls, LDLs deposit it there

284
Q

what are the main categories of liver function?

A 
carbohydrate metabolism
protein metabolism
lipid metabolism
transport of lipids
storage & drug detoxification
285
Q

how does the liver function in carbohydrate metabolism?

A

1) monosaccharides absorbed from small intestine into blood, enter hepatocytes, converted to glucose
2) noncarbohydrates converted to glucose by gluconeogenesis
3) glucose molecules are bonded together to form glycogen by glycogenesis
4) glucose molecules are released from glycogen by glycogenolysis

286
Q

how does the liver function in protein metabolism?

A

1) deamination (amine group removed from amino acids) NH2 converted to urea & enters blood where eliminated by kidney. remaining components oxidized in cellular respiration to generate ATP from liver
2) amino acids used to form proteins, including plasma proteins
3) transamination: amino acids converted from one form to another

287
Q

how does the liver function with lipid metabolism?

A

1) fatty acids joined with glycerol to form triglycerides (lipogenesis)
2) fatty acids released from triglycerides (lipolysis)
3) fatty acids broken down into acetyl CoA (beta oxidation)
4) acetyl CoA changed to ketone bodies (water-soluble molecules) - released into blood, transported to other cells - can be oxidized in cell respiration pathways
5) acetyl CoA used in cholesterol synthesis - cholesterol released into blood w/in VLDL & some used to form bile salts

288
Q

how does the liver function with lipid transport?

A

transports both triglycerides & cholesterol w/in VLDLs and LDLs from liver to peripheral tissues
empty HDLs pick up lipids from peripheral tissues & blood & return as full HDLs to liver

289
Q

what are other functions of the liver?

A

absorption of bilirubin (derived from heme group of hemoglobin) and eliminated as component of bile
storage site for vitamins (ADB) and minerals (Fe,Zn,Cu,Mg,Mn)
detoxification of drugs
hormone breakdown

290
Q

what are the four stages of cellular respiration?

A

glycolysis
intermediate stage
citric acid cycle
electron transport system

291
Q

describe glycolysis

A 
anaerobic
cytoplasm of cell
glucose oxidized to 2 pyruvate molecules
2 ATP molecules formed
2 NAD+ molecules turn into 2 NADH molecules
292
Q

describe the intermediate stage

A

multienzyme step
pyruvate converted to acetyl CoA
molecule of CO2 is formed by decarboxylation
1 molecule of NADH is produced

293
Q

describe the citric acid cycle

A

acetyl CoA binds to oxaloacetic acid to form citric acid
2 C released as part of CO2 by decarboxylation
1 ATP, 1FADH2, and 3 NADH molecules are produced per turn
intermediate stage & citric acid cycle happen TWICE because there are 2 pyruvate molecules formed from oxidation of each glucose molecule entering glycolysis

294
Q

describe the electron transport system

A

transfer of H and an e- from coenzymes NADH and FADH2. ATP formation occurs through oxidative phophorylation.

295
Q

how can amino acids be used in cellular respiration?

A

must be deaminated in liver first
then can enter pathway of glycolysis, intermediate stage, or at specific points in the citric acid cycle
amine group is converted to urea & peed out

296
Q

where does glycerol enter the pathway of cellular respiration?

A

glycolysis
it is converted to glucose through gluconeogenesis w/in liver
carbons of fatty acids are moved two at a time to form CoA which then enters citric acid cycle

297
Q

what is the basal metabolic rate?

A

amount of energy used when an individual is at rest & not eating

298
Q

what is total metabolic rate?

A

amount of energy used by the body, including energy needed for physical activity
BMR + metabolism associated w/physical activity

299
Q

In the pancreatic islet, what are the cells

A

Alpha cells - secrete glucagon

Beta cells - secrete insulin

a&p (5 decks)

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