Download or ALIMENTARY SYSTEM

DIGESTIVE SYSTEM - III
(or ALIMENTARY SYSTEM)
Digestive Tract
(or Alimentary Canal)
林谷峻
生物及解剖學科
Small Intestine
Duodenum
- 25 cm
Jejunum
- 2.5 m (2/5)
Ilium - 3.5 m (3/5)
Duodenum and Pancreas
Duodenum (呈C型，分為四段)
first part
(superior part)
second part
(descending
part)
Pancreas
fourth part
(ascending part)
third part
(horizontal part)
Development of Duodenum
a) 十二指腸由前腸末端與中腸前端共同發育而來，其交接處在總膽管開口處。於第
四週開始，生長甚速，向腹面形成C字型環。當胃旋轉時亦隨著轉向右側。於第5，6
週，暫時閉鎖，胚體期末了才又打通。
b) 血液由腹腔動脈及上
腸繫膜動脈供應。
c) 十二指腸處有肝臟與
胰臟
4 wks
5 wks
5 wks
6 wks
Liver
Hepatic diverticulum
1. Hepatic cords
(primordium of liver)
2. Biliary apparatus
- hepatic ducts
- gallbladder – cystic
duct
- common bile duct
Pancreas
Dorsal and ventral buds fuse
head, body, and tail
d) 先天畸形
i. 十二指腸狹窄(duodenal stenosis)：由於再打通不全或由環狀胰
(annular pancreas）之壓力所引起。胃內物(含膽汁)常吐出。
ii.十二指腸閉鎖(duodenal atresia)：不常見，部份伴隨Down syndrome
Vacuolization
Normal
Double bubble
Stenosis
Atresia
Development of the midgut
中腸(midgut)之衍生物包括：
a) 總膽管入口後之十二指腸及全部的小腸。
b) 盲腸(cecum)，闌尾(vermiform appendix)，昇結腸(ascending colon)，橫結腸
(transverse colon) 的近端1/2至2/3部份。以上部位皆由上腸繫膜動脈(superior
mesenteric artery) 供應。
Midgut loop
1. 中腸發育迅速，向腹側方击出，形成U字型之中腸環(midgut loop)。約在第六週時，
因 腹 腔 為 肝 臟 、 腎 臟 所 佔 而 擠 入 臍 帶 內 ， 稱 為 生 理 學 上 的 臍 疝 氣 (physiological
umbilical herniation) 。 於 第 十 週 收 回 ， 稱 為 中 腸 疝 氣 的 復 原 (reduction of the
midgut hernia)，其可能的機轉為腹腔變大，而肝腎所佔的空間變小。
Physiological hernia in a fetus (about 58 days)
2. 中腸環於卵黃莖(管)(yolk stalk or vitelline duct)處分為頭肢(cranial limb)
及尾肢(caudal limb)。頭肢衍化為十二指腸(duodenum)，空腸(jejunum)，迴腸
(ileum)；除十二指腸前端外，以腸繫膜連接於後腹壁。尾肢形成盲腸憩室(cecal
diverticulum)，升結腸及橫結腸近側部份。闌尾位置變異頗多。除闌尾外，皆位於後
腹腔。
3. 當中腸在臍帶中時，曾依逆時針方向作90o旋轉，等回到腹腔後又作180o旋
轉，使闌尾由上方轉向下方，結果共作270o旋轉。
中腸的旋轉
90°
90°
90°
4. 中腸的先天畸形 (Anomalies of Midgut)：
a) 先天性臍疝氣(congenital omphalocele)：胚胎第10週時，小腸未回到
腹腔中，而由羊膜腔內胚層細胞覆蓋而引起，嚴重者，為腹部臟器外翻
(eventration of the abdominal viscera)。
b) 臍帶疝氣(umbilical hernia)：小腸回到腹腔後，因臍帶癒合不全，击出
而造成。其击出物為皮膚及皮下組織所覆蓋。
10
c) 中腸旋轉不正常(abnormalities of midgut rotation)：
中腸的不旋轉(nonrotation of the midgut)：常見，
有時稱左結腸(left-side colon)，無症狀，但有時發
生腸扭結(volvulus)。
Normal
Nonrotation 不旋轉
Mixed rotation
and volvulus
混合旋轉及扭結
Reversed
rotation
反向旋轉
Subhepatic
cecum
and appendix
Internal hernia內部疝氣
Midgut
volvulus
11
d) 邁克耳氏憩室(Meckel diverticulum)：又稱迴腸憩室(ileal
diverticulum) 是消化道最常見的先天畸形之一，發生率約為
2~4%。為 yolk stalk 遺留而發生3~6公分的指形隱窩。有時會發
炎，其症狀如闌尾炎
12
Plicae circulares
(小腸的共同特徵)
13
Histology of small intestine
A. Mucosa – plicae circulares 環狀皺襞，villi 絨毛
1. Simple columnar epithelium
a. Enterocytes (intestinal absorptive cells) 腸(吸收性)細胞
– striated border, junctional complex, lateral plication 側摺襞
b. Goblet cells – mucinogen granules 黏液素原顆粒, secret mucus
c. Paneth cells 班氏細胞 – secret lysozyme 溶菌酶, phagocytotic activity
d. Enteroendocrine cells
– secret CCK (cholecystokinin), secretin, and GIP (gastric inhibitory peptide)
e. Intermediate cells 中間細胞
f. M cells (microfold cells) – microfold, nearly squamous, endocytotic vesicle
2. Intestinal villi – lacteal 乳糜管in lamina propria
3. Intestinal glands (crypts of Lieberkühn)
4. Lamina propria – GALT, Peyer’s patches 培氏斑 (in ileum)
5. Muscularis mucosa - inner circular, outer longitudinal layer
B. Submucosa – plicae circulares
- Brunner’s (or duodenal) glands (in duodenum)
C. Muscularis externa
– inner circular, outer longitudinal layer
– Auerbach’s plexus
– muscular contraction: segmentation 分節運動, peristalsis 蠕動
D. Serosa or adventitia (in duodenum)
Plicae circulares – form by mucosa and submucosa
Plicae circulares and villi
Duodenum
Jejunum
Ileum
Brunner’s gland
Peyer’s patch
leaf-like villi
finger-like villi
short leaf-like villi
Special histological structures of small intestine
to increase absorptive surface
A. Lengthening and
convolution of the gut
B. Plicae circulares
C. Villi
D. Microvilli 
striated border
E. Glycocalyx
A. Mucosa - Villi and intestinal glands
Intestinal villi
Villus
Intestinal glands
Intestinal glands
- crypts of Lieberkühn
Villus
Intestinal glands
- crypts of
Lieberkühn
Microvilli of the
striated border
Cells of intestinal glands
Enterocyte or
gastric inhibitory peptide (GIP)
and motilin
a. Enterocytes (intestinal absorptive cells) 腸(吸收性)細胞
– striated border, junctional complex, lateral plication 側摺襞
– digests and absorbs nutrients
Diagram of
immunoglobulin A (IgA)
secretion and transport
dIgA: dimeric IgA antibody
pIgR: Polymeric immunoglobulin
SC: secretory component
sIgA: secretory IgA
22
b. Goblet cells 杯狀細胞
– mucinogen granules 黏液素原顆粒, produce mucus
c. Paneth cells 斑氏細胞
 have secretory granules which contain lysozyme 溶菌酶,
phagocytotic activity
Figure 12.107
Part of a transverse section of the ileum,
showing Paneth cells containing
orange-stained zymogen granules at the
base of an intestinal gland.
'Undifferentiated' epithelial cells are
also visible. Mallory's azan stain.
d. Enteroendocrine cells
– secret CCK (cholecystokinin), secretin, and GIP (gastric
inhibitory peptide)
e. Intermediate cells 中間細胞
– have characteristics of both immature absorptive cells and
goblet cells
f. M cells (microfold cells) M細胞(微褶細胞)
– microfold, endocytotic vesicles, an antigen-transporting cell, CD4+ T cells
Lymphocytes
(microfold)
M cells
overlie
Peyer’s
patches
and other
large
lymphatic
nodules
Lacteal in the lamina propria
of the villus
Figure 12.103
A three-dimensional reconstruction of the
architecture of the intestinal villi and subjacent wall
(the principal layers of the latter are indicated):
arteries and arterioles (red), veins and venules (blue),
central lacteals and other lymphatic channels
(orange), aggregations of lymphocytes (yellow),
neural elements (green), non-striated muscle fibres
(magenta), fibroblasts (white). Note the orifices of
the intestinal crypts (of Lieberkühn). Types of cells
in the epithelium include absorptive cells, goblet
cells and entero-endocrine cells. Arrows indicate the
direction of cell migration. The various layers are
not drawn to scale.
Peyer’s patch within
Lamina propria
of the ileum
B. Submucosa
 submucosal (or Brunner’s or duodenal) glands in the duodenum
- cells have both zymogen- and mucus-secreting
- neutral and alkaline glycoproteins and bicarbonate ions
Mucosa
Submucosa
Brunner’s glands
C. Muscularis externa
 inner thick circular, outer thin longitudinal layer
– Auerbach’s plexus
– muscular contraction - peristalsis 蠕動& segmentation 分節運動
Peristalsis
Segmentation
D. Serosa or adventitia (in part of duodenum)
差異
plicae circulares
空腸
Peyer’s patch
迴腸
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Large intestine
Position: form ileum to anal
(from abdomen cavity to pelvic cavity)
Cecum (盲腸)
Appendix (闌尾)
accending colon (升結腸)
transverse colon (橫結腸)
descending colon (降結腸)
sigmoid colon (乙狀結腸)
rectum and anal canal(直腸及肛管)
(pelvis and perineum)
Successive stages in the development of the cecum and appendix
6 wks
8 wks
At birth
12 wks
Adult
34
Development of the hindgut
後腸(hindgut)之衍生物包括：
a) 橫結腸遠端1/2部份，降結腸(descending colon)，乙狀結腸(sigmoid colon)，
直腸(rectum)，肛管上側部份(superior portion of anal canal)
b) 膀胱及大部分尿道上皮以上血液由下腸繫膜動脈(inferior mesenteric artery)
供應。
1. 後腸由中腸延伸到泄殖腔膜(cloacal membrane)，後腸末端膨大部份即泄
殖腔(cloaca)。此腔後被間葉細胞形成的泌尿直腸中隔(urorectal septum)
所分，形成背面的直腸肛管(anorectal canal)之上部及腹面之泌尿生殖竇
(urogenital sinus)。第七週泌尿直腸中隔即到達最下方與泄殖腔膜癒合，此
區後形成會陰體(perineal body)，並將泄殖腔膜分為背部之肛膜(anal mem.)
及腹面之泌尿生殖膜(urogenital membrane)。其後圍在肛膜周圍之間質將
外面之外胚層頂起，即為原肛或稱肛門凹(anal pit)。第八週時，肛門破裂。
Allantois
Hindgut
Urogenital
membrane
Cloacal
membrane
Cloaca
Urorectal septum
Anal membrane
Cloaca into the rectum and urogenital sinus
by the urorectal septum
4 wks
6 wks
7 wks
2. 肛管的上面約2/3由後腸來的，下面1/3則由原肛發育而來。由原肛外胚層
形成的上皮和由後腸內胚層而來的上皮交接處為櫛狀線(pectinate line)，
此線為肛膜從前的位置。Anocutaneous line –“white line”
37
3. 後腸的先天畸形(Anomalies of Hindgut)：
a) 先天性巨結腸(congenital megacolon or Hirschsprung disease)：
結腸的一部份膨大，由於位於此膨大結腸之遠側結腸的腸肌叢(myenteric
plexus)中缺神經節細胞，無法蠕動，致此段結腸阻塞，引起前段結腸膨大。
b) 肛門閉鎖與直腸肛門異常(imperforate anus & related anorectal
anomalies) : 由於泌尿直腸中膈發育不全，無法將泌尿生殖部與肛門直腸部完
全分隔。
c) 具瘻管或不具瘻管的肛門不發育(anal agenesis, with or without a
fistula): 肛管末端閉塞成盲管或有異位開口(異位肛門，ectopic anus)及瘻
管。
d) 肛門狹窄(anal stenosis)： 肛門位置正常，但肛管變窄，可能由於泌尿生殖
中隔生長偏離所致。
e) 肛門之膜狀閉鎖(membranous
atresia of anus)：肛門位置正
常，但一層薄組織將肛管與外界
分隔開，乃肛門的膜於第8週時
不能穿孔所致。
♀
♂
Membranous anal atresia
(Imperforate anus)
♂
f) 具瘻管或不具瘻管的肛門直
腸不發育(anorectal agenesis,
with or without a fistula)
：直腸形成盲管或有瘻管通到膀
胱或尿道(男性)或陰道(女性)上。
g) 直腸閉鎖(rectal atresia)：
♂
♂
♀
Anal agenesis with
a perineal fistula
♀
Anorectal
agenesis
♀
Anorectal agenesis
♀
Cut off mesentery
Large intestine(5 subdivision)
Colon(4) and rectum
Transverse colon
Accending colon
cecum
appendix
Decending colon
Sigmoid colon
uterus
rectum
bladder
Transverse colon
Hepatic flexure
Ascending colon
Splenic flexure
Descending colo
Cecum
Sigmoid colon
appendix
Rectum
Anal canal
The cecum is the first part of the large intestine; it is continuous with the
ascending colon. The cecum is a blind intestinal pouch, approximately 7.5 cm in
both length and breadth.
(迴盲瓣)
Ileal papilla
Appendix (闌尾)
The appendix (vermiform appendix) is a blind intestinal diverticulum (6-10 cm
in length) that contains masses of lymphoid tissue. It has a short triangular
mesentery, the mesoappendix, which derives from the posterior side of the
mesentery of the terminal ileum.
大腸與小腸的表面差異
Teniae coli, haustra and appendices epiploicae
結腸袋(憩室)
haustra
(腸脂垂)
(結腸
帶)
LARGE INTESTINE
 cecum (- vermiform appendix), colon (ascending, transverse,
descending, and sigmoid colon), rectum, and anal canal
Teniae coli
結腸帶
Haustra coli
結腸袋
Iliocecal valves
Omental appendices 網膜附件
(or Epiploic appendages, appendices epiploicae 腸脂垂)
Histology of large intestine
Cecum and colon
A. Mucosa
 smooth tube -----no villi or plica
 intestinal glands (crypt of Lieberkühn) fill the mucosa
 absorptive cells absorb water, more goblet cells  mucus,
enteroendocrine cells, undifferentiated cells
 lamina propria – collagen table, no lymphatic vessel
B. Submucosa & mucosa contain lymphatic nodules
C. Muscularis externa
 internal circular layer is normal
 outer longitudinal muscle
 taeniae coli = shorter bands
 haustra (pouches) formed
D. Serosa or adventitia (in ascending and descending colon)
 epiploic appendages
* Appendix - large amounts of lymphatic t.; no taeniae coli; serosa
* Rectum - transverse rectal folds, no teniae coli, no serosa
Appendix
Colonic mucosa
Colon
Crypt of
Lieberkühn
Taeniae coli
Additional structural features in lamina propria
 collagen table 膠原板 – regulate water and electrolyte transport
 GALT extensively developed – microorganisms and noxious end products
 pericryptal fibroblast sheath 腺窩周圍纖維母細胞鞘 – macrophages-like
 absence of lymphatic vessels – the slow rate of metastasis
Collagen table
Rectum and anal canal
Anal canal - anal column, anal sinus
1. Mucosa
a. Epithelium
i. Colorectal zone: simple columnar
ii. Anal transitional zone: stratified
columnar, muscularis mucosae x
iii. Squamous zone: stratified squamous
b. Anal glands - extend into submucosa
2. Submucosa – rectal venous plexus靜脈叢
*Internal hemorrhoids 內痔
3. Muscularis externa – inner circular
 internal anal sphincter
* External anal sphincter:
striated muscle
Anal orifice - perianal skin
– circumanal glands
Anal canal
Blood supply of gut
Celiac A:
liver, spleen, stomach,
and proximal duodenum
Sup. Mesentery A:
small intestine and
proximal 2/3 transverse
colon
Inf. Mesentery A:
distal 1/3 transverse
colon and the rest of
colon
Blood supply:
Celiac a: liver, spleen and stomach
Sup. Mesentary a:small intestine and proximal 2/3
transverse colon
Inf. Mesentary a:distal 1/3 transverse colon and the
rest of colon
mesentery
(腸繫膜:
二層腹膜的褶疊)
Celiac trunk
Superior & inferior mesentery artery
Veins of stomach, duodenum, and spleen
Veins of
large intestine
60
Superior mesentery artery syndrome (上腸系膜動
脈症候群)
Innervation of GI tract: Vagus n
Innervation of guts: autonomic system
Parasympathetic(red):
Vagus n
Lumbosacral pluxes
Prevertebral sympathetic
chain(blue):
celiac ganglion
sup. mesentary ganglion
Inf. mesentary ganglion
Principles of innervation
The gut has intrinsic and extrinsic innervation. The intrinsic innervation of the gut arises from a plexus of
ganglion cells and interganglionic nerve fibres (Auerbach's) lying between the circular and longitudinal
muscle coats from the esophagus to the rectum. A second plexus (Meissner's) lies in the submucosa, with
connections between the two networks. The extrinsic innervation is derived from the sympathetic splanchnic
nerves and from from the parasympathetic vagus. Sensory neurons carrying sensations of constriction or
distention of the gut tube are located in spinal dorsal root ganglia and vagal ganglia.
Principles of innervation
The gut has intrinsic and extrinsic innervation. The intrinsic innervation of the gut arises from a plexus of ganglion cells
and interganglionic nerve fibres (Auerbach's) lying between the circular and longitudinal muscle coats from the
esophagus to the rectum. A second plexus (Meissner's) lies in the submucosa, with connections between the two
networks. The extrinsic innervation is derived from the sympathetic splanchnic nerves and from from the
parasympathetic vagus. Sensory neurons carrying sensations of constriction or distention of the gut tube are located in
spinal dorsal root ganglia and vagal ganglia.
Inflammatory Bowel Disease (IBD)
Inflammatory bowel disease (IBD) is a chronic relapsing idiopathic
inflammation of the gastrointestinal tract.
The two main forms of IBD – Crohn’s disease and ulcerative colitis – have
many similarities, but there are also several clinical and pathological differences.
Nat. Rev. Immunol. (2003) 3:521-533
66
Anastomoses between portal and system
1.左胃靜脈←→奇靜脈支
2.直腸上靜脈←→直腸中、下靜脈
3.臍旁靜脈←→前腹壁的表淺靜脈
4.升、降結腸，十二指腸，胰臟，肝臟的靜
脈支←→後腹壁走向的腎、腰與橫膈的靜脈
支
1
4
3
2
Morison’s pouch:
a space between liver, kidney and colon
Clinical importance: blood or extraperitoneum fluid
accumulated
Suprapubic view
Direct Inguinal Hernia
The direct inguinal hernia,
a type of inguinal hernia,
enters through a weak point
in the fascia of the
abdominal wall, and its sac
is noted to be medial to the
inferior epigastric vessels.
Direct inguinal hernias are
the same in men and women.
臍靜脈
臍動脈