Human Anatomy : Digestive System

7/21/2019 Human Anatomy : Digestive System

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General Structure and

Functionsof the Digestive System Organs of the Digestive System to:

ngest the food! "rans#ort the food! Digest the food into smaller usa$le

com#onents!

A$sor$ the necessary nutrients intothe $loodstream!

%&#el the 'aste #roducts from the$ody!



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Functionsof the Digestive System )om#osed of t'o se#arate

categories of organs: digestive organs accessory digestive organs!

Digestive organs collectively ma*e

u# the: gastrointestinal +G, tract! Also called:

the digestive tract alimentary canal!



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Functionsof the Digestive System Accessory digestive organs:

do not form the G tu$e can develo# as outgro'ths are connected to the G tract +some $y ducts,

Assist the G tract in the digestion of food! nclude:

"eeth "ongue Salivary glands iver Gall$ladder

ancreas


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Digestive System

Functions ngestion Digestion: $rea* do'n of large #articles of food

mechanical digestion chemical digestion

ro#ulsion #eristalsis segmentation

Secretion: digestive en4ymes hormones

A$sor#tion: from e&ternal environment into internal environment across mucosa

%limination of 'astes +defecation,



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Oral )avity +mouth, %ntrance to the G tract! nitial site of digestion:

mechanical digestion +via mastication, chemical digestion +via en4ymes in saliva,!

5ounded anteriorly $y the teeth and li#s 5ounded #osteriorly $y the oro#haryn&! Su#erior $oundary is formed $y the hard

and soft #alates! Floor or inferior surface of the oral cavity

the tongue the mylohyoid muscle covered 'ith mucosa!



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Oral )avity +mouth, "'o regions of the oral cavity

7esti$ule is the s#ace $et'een the chee*s or li#s andthe gums!

Oral cavity #ro#er! "he lateral 'alls are formed $y the chee*s!

)ontain $uccinator muscles i#s +la$ia,!

Or$icularis oris muscle

8eratini4ed strati9ed suamous %" Gingivae or gums!

Dense regular )" ;on*eratini4ed %"

a$ial frenulum!



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alate Hard #alate

Anterior t'o-thirds of the #alate hard and $ony

Soft #alate osterior one-third soft and muscular #rimarily com#osed of s*eletal muscle! %&tending inferiorly from the #osterior #art of

the soft #alate is the uvula! =hen s'allo'ing the soft #alate and the

uvula elevate to close o> the o#ening of

the naso#haryn&!



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alate Fauces re#resent the o#ening $et'een

the oral cavity and the oro#haryn&!

Fauces are $ounded $y #aired muscularfolds: glosso#alatine arch +anterior fold, #haryngo#alatine arch +#osterior fold,

alatine tonsils are housed $et'een thearches!



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"ongue An accessory digestive organ Formed from:

s*eletal muscle covered 'ith lightly *eratini4ed strati9ed

suamous e#ithelium!

?ani#ulates and mi&es ingested materialsduring che'ing

Forms the $olus! a glo$ular mass of #artially digested material

erforms im#ortant functions in s'allo'ing!



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"ongue nferior surface of the tongue

attaches to the @oor of the oral cavity

5y the lingual frenulum! ;umerous small #roections +#a#illae,

cover the su#erior +dorsal, surface!

osterior surface contains lingualtonsils!

S*eletal muscles move the tongue!



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Salivary Glands )ollectively #roduce and secrete

saliva!

a @uid that assists in the initialactivities of digestion

7olume of saliva secreted dailyranges $et'een 1!. and 1! ! ?ost is #roduced during mealtime Smaller amounts are #roduced

continuously to ensure that the oral

cavity remains moist!



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Salivary Glands )om#onents of saliva

=ater: ma*es u# //C

Amylase: 9rst ste# of chemical digestion yso4yme: antimicro$ial

Functions ?oisten food

Food molecules into solution: taste Form $olus: for s'allo'ing )leanse oral cavity!



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Salivary Glands "hree #airs of large multicellular

salivary glands: #arotid glands

su$mandi$ular glands

su$lingual glands



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"he arotid Glands argest salivary glands!

located anterior and inferior to the

ear #artially overlying the masseter

muscle!

roduce a$out 20(.C of saliva conducted through the #arotid duct to

the oral cavity!



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"he Su$mandi$ular Glands nferior to the $ody of the

mandi$le!

roduce most of the saliva +a$out6.03.C,!

ducts o#ens through a #a#illa in

the @oor of the mouth lateral to the the lingual frenulum!



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"he Su$lingual Glands nferior to the tongue

internal to the oral cavity mucosa!

%ach gland has multi#le tiny su$lingualducts o#en onto the inferior surface of the oral

cavity

#osterior to the su$mandi$ular duct #a#illa!

)ontri$ute only a$out (0C of the totalsaliva!



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"eeth )ollectively *no'n as the dentition! es#onsi$le for mastication

9rst #art of the mechanical digestion!

A tooth has: e&#osed cro'n constricted nec* one or more roots

oots of the teeth 9t into dental alveoli are soc*ets 'ithin the alveolar #rocesses on $oth the ma&illae and the mandi$le!

)ollectively the roots the dental alveoli andthe #eriodontal ligament that $inds the roots tothe alveolar #rocesses form a gom#hosis oint!



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"eeth "'o sets of teeth 2. deciduous teeth also called Emil* teeth eru#t

$et'een 6 months and (. months after $irth!

"hese teeth are eventually lost and re#laced $y (2#ermanent teeth! "he more anteriorly #laced #ermanent teeth tend to

a##ear 9rst follo'ed $y the #osteriorly #laced teeth! "he last teeth to eru#t are the third molars often called

E'isdom teeth in the late teens or early 2.s! Often the a' lac*s s#ace to accommodate these 9nal

molars and they may either emerge only #artially orgro' at an angle and $ecome im#acted!

m#acted teeth cannot eru#t #ro#erly $ecause of theangle of their gro'th!



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haryn& evie'

haryngeal constrictors

nnervated $y the vagus nerves



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General arrangement of

a$dominal G organs eritoneum

arietal #eritoneum

7isceral #eritoneum eritoneal cavity

ntra#eritoneal organs

etro#eritoneal organs



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General arrangement of

a$dominal G organs ?esentaries

Dou$le layered folds of #eritoneum Greater omentum esser omentum ?esentery #ro#er

Sus#ends small intestine from #osterior 'all ofa$domen

?esocolon Sus#ends large intestine

eritoneal ligament eritoneum that attaches one organ to another



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General Histology of G

Organs from the eso#hagus through the large

intestine a tu$e com#osed of four concentric layers called

tunics!

From dee# to su#er9cial these tunics are: the mucosa

the su$mucosa su$mucosal nerve #le&us +?eissner #le&us,

the muscularis myenteric #le&us +Auer$ach #le&us,

the adventitia or serosa



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%so#hagus "u$ular #assage'ay

haryn& to stomach 5olus A$out 2 cm in adult %so#hageal hiatus: through dia#hragm

Histology ?ucosa: non*eritini4ed strati9ed suamous e#!

Su$mucosa: thic* elastic 9$ers mucous glands ?uscularis: inner circular outer longitudinal 5oth s*eletal and smooth

Adventitia



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%so#hagus Su#erior eso#hageal s#hincter:

S*eletal muscle

=here #haryn& and eso#hagus meet nferior eso#hageal s#hincter

Also cardiac s#hincter

)ircular smooth muscle Ori9ce $et'een eso#hagus and

stomach



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Stomach General

-sha#ed

Functions Digestion

)hemical

?echanical

esults in chyme imited a$sor#tion



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Stomach Gross anatomy

)ardia )ardiac ori9ce

Fundus 5ody ylorus

yloric s#hincter yloric ori9ce

Greater curvature Greater omentum

esser curvature esser omemtum

Gastric folds +rugae,



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Stomach Histology

?ucosa: sim#le columnar Gastric #its Gastric glands

?uscularis

( layers nner o$liue ?iddle circular

Outer longitudinal



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Small ntestine Finishes chemical digestion es#onsi$le for a$sor$ing most of the nutrients!

ngested nutrients s#end at least 12 hours in the small

intestine! thin-'alled tu$e

a$out 6 meters +2. feet, in length! coiled

%&tends from the #ylorus of the stomach to thececum of the large intestine occu#ies a signi9cant #ortion of the a$dominal cavity!



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Small ntestine "he duodenum 9rst segment of the small intestine! a##ro&imately 2 centimeters +1. inches, long originates at the #yloric s#hincter maor duodenal #a#illa

"he eunum middle region of the small intestine! a##ro&imately 2! meters +3! feet, ma*es u# a##ro&imately t'o-9fths of the small intestines

total length! #rimary region for chemical digestion and nutrient a$sor#tion

"he ileum is the last region of the small intestine! a$out (!6 meters +1.!B feet, in length forms a##ro&imately three-9fths of the small intestine! terminates at the ileocecal valve

s#hincter that controls the entry of materials into the large

intestine!



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arge ntestine a##ro&imate length of 1! meters + feet,

diameter of 6! centimeters +2! inches,!

A$sor$s most of the 'ater and electrolytes from the

remaining digested material! =atery material that 9rst enters the large intestine soon

solidi9es and $ecomes feces!

Stores fecal material until the $ody is ready to defecate!

A$sor$s a very small #ercentage of nutrients stillremaining in the digested material!

)om#osed of four segments: the cecum colon rectum anal canal



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Accessory Digestive

Organs The liver

com#osed of four incom#letely se#arated lo$es su##orted $y t'o ligaments

ight lo$e

eft lo$e

Falciform ligament

ound ligament )audate lo$e

Iuadrate lo$e



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Functions of "he iver roduce $ile!

a greenish @uid that $rea*s do'n fats into small dro#letsto assist in their chemical digestion

Deto&ify drugs meta$olites and #oisons! Store e&cess nutrients and vitamins and release them

'hen they are needed!

Synthesi4e $lood #lasma #roteins such as al$uminsglo$ulins and #roteins reuired for $lood clotting!

hagocyti4e de$ris in the $lood! Hel# $rea* do'n and recycle com#onents of aged

erythrocytes and damaged or 'orn-out formedelements!



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Accessory Digestive

Organs Gallbladder

concentrates $ile #roduced $y the liver and storesthis concentrate until it is needed for digestion

cystic duct connects the gall$ladder to the common$ile duct

can hold a##ro&imately <. to 6. milliliters ofconcentrated $ile



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Accessory Digestive

Organs Pancreas

mi&ed gland $ecause it e&hi$its $oth endocrine ande&ocrine functions

%ndocrine functions are #erformed $y the #ancreaticislets!

%&ocrine activity results in the secretion of digestiveen4ymes collectively called #ancreatic uice into theduodenum!



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Accessory Digestive

Organs "he $iliary a##aratus!

net'or* of thin ducts that carry $ile from the liver and gall$ladder to the duodenum

the left and right lo$es of the liver drain $ile into theleft and right he#atic ducts res#ectively

the left and right he#atic ducts merge to form asingle common he#atic duct

the cystic duct attaches to the common he#atic duct

and carries $ile to and from the gall$ladder



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Human Anatomy : Digestive System