Embryo Test 4 Notes

Front 1

Pharyngeal apparatus – ?

Back 1

Pharyngeal apparatus – not branchial in human

Front 2

Pharyngeal arches - ?

Back 2

Pharyngeal arches – bars of mesenchyme separated by clefts exteriorly and pouches internally

Front 3

Arch one – mandibular arch
a maxillary process;
b mandibular process;
c musculature –
d innervation –

Back 3

Arch one – mandibular arch, most complex split into 2 parts

a maxillary process;
b mandibular process;
c musculature –
d innervation –

Front 4

Arch one – mandibular arch

maxillary process;

Back 4

maxillary process; maxilla, zygomatic, part of temporal - petrous

Front 5

Arch one – mandibular arch

mandibular process -

Back 5

mandibular process; Meckel’s cartilage; mandible, incus, malleus

Front 6

Arch one – mandibular arch

musculature –

Back 6

musculature –
muscles of mastication; mylohyoid, anterior belly of digastric, tensor tympani, tensor palatine

Front 7

Arch one – mandibular arch

innervation –

Back 7

innervation –
motor – mandibular division of CN V; sensory – all three divisions of CN V

Front 8

Arch two – ?

skeletal element –

musculature –

innervation –

Back 8

Arch two – hyoid arch

Front 9

Arch two – hyoid arch

skeletal element –

Back 9

skeletal element –

stapes, styloid process of temporal bone, stylohyoid ligament, lesser horn and upper part of body of hyoid

Front 10

Arch two – hyoid arch

musculature –

Back 10

musculature –

stapedius, stylohyoid, posterior belly digastric, muscles of facial expression

Front 11

Arch two – hyoid arch

innervation –

Back 11

innervation – CN VII, facial

Front 12

Arch three

skeletal –
musculature –
innervation –

Back 12

Arch three

skeletal –
musculature –
innervation –

Front 13

Arch three

skeletal –

Back 13

skeletal – l

ower body and greater horn of the hyoid

Front 14

Arch three


musculature –

Back 14

musculature –

stylopharyngeus

Front 15

Arch three


innervation –

Back 15

innervation –

CN IX, glossopharyngeal

Front 16

Arch 4-6 ---

Back 16

Arch 4-6 --- 5 doesn’t form

Front 17

Arch 4-6 --- 5 doesn’t form

cartilages of larynx –

larynx - air only

Back 17

cartilages of larynx –

thyroid, cricoid, arytenoid, corniculate, cuneiform

Front 18

Arch 4-6 --- 5 doesn’t form

musculature –

pharynx - air & food

Back 18

musculature –

arch 4- cricothyroid, constrictors of pharynx;

arch 6 – intrinsic muscles of larynx
innervation – CN X, vagus

Front 19

Arch 4-6 --- 5 doesn’t form

arch 4 –

Back 19

arch 4 – superior laryngeal N. – constrictors

Front 20

Arch 4-6 --- 5 doesn’t form

arch 6 –

Back 20

arch 6 – recurrent laryngeal N. – intrinsic

Front 21

Pharyngeal pouches – ?
how many total?

which 2 pouches are together?

Back 21

Pharyngeal pouches – dilation of wall of endodermal tube

5 pouches

4 and 5 are together

Front 22

Pharyngeal pouches

Pouch 1

b/t arch 1 & 2, endoderm, ear structure development

Back 22

Pouch 1 – tubotympanic recess

contacts cleft 1

distal portion forms primitive tympanic (middle ear) cavity

proximal portion forms eustacian tube

Front 23

Pharyngeal pouches

Pouch 2

Back 23

Pouch 2

tonsillar crypts of palatine tonsil

Front 24

Pharyngeal pouches

Pouch 3 - wing

Back 24

Pouch 3

forms dorsal and ventral wing

dorsal wing – inferior parathyroid gland

ventral wing – thymus

Front 25

Pharyngeal pouches


pouch 4

Back 25

pouch 4

forms superior parathyroid gland

Front 26

Pharyngeal pouches

pouch 5

Back 26

pouch 5 forms ultimobranchial body (lose contact w/ surface) – incorporated into thyroid gland to form parafollicular cells (produce calcitonin hormone)

Front 27

Pharyngeal clefts – ?

how many are there?

Back 27

Pharyngeal clefts – visible outside

grooves on external surface between arches

4 pharyngeal clefts

Front 28

Pharyngeal clefts

First cleft - ear canal

Back 28

First cleft forms external acoustic meatus - cleft 1, like pouch 1

Front 29

Pharyngeal clefts

clefts 2-4

Back 29

Clefts 2-4

cut off from surface by rapid growth of arch 2

form temporary cervical sinus

Front 30

Tongue
3 parts

arch 2 is not part on tongue

Back 30

anterior 2/3; oral part(root is arch 3 & 4); arch 1

posterior 1/3; pharyngeal (root)

innervation of the tongue

Front 31

Tongue

anterior 2/3; oral part; arch 1

Back 31

anterior 2/3; oral part; arch 1

a. tuberculum impar; median tongue bud

b. lateral lingual swellings; distal tongue buds

c. median sulcus (superficial) and lingual septum (internal) mark fusion of lateral lingual swellings
also line of fusion

d. separated from root by transverse groove – the terminal sulcus

Front 32

Tongue

posterior 1/3; pharyngeal (root)

Back 32

posterior 1/3; pharyngeal (root)

a. caudal to foramen cecum (opening of thyroglossal duct)

b. copula (arch 2) – overgrown and disappears

c. hypobranchial eminence (arches 3 and 4) separated from oral part by terminal sulcus

Front 33

Tongue

innervation of the tongue

Back 33

innervation of the tongue

a. motor – CN XII (hypoglossal nerve); myoblasts derived from occipital myotomes

b. taste
1). anterior – CN VII; facial nerve; chorda tympani
2). posterior – CN IX; glossopharyngeal nerve

c. general sensory

1). anterior – mandibular division of CN V

2.) posterior – mostly CN IX; some CN X just above epiglottis

parahyroid gland - arch 3 & 4

Front 34

Thyroid

Back 34

Thyroid

Begins week 4; first endocrine gland to appear
Thickening in pharynx forms thyroid diverticulum

Connected to tongue via thyroglossal duct (back of tongue) opening the back of oral part of tongue

Two lobes connected by isthmus

Pyramidal lobe in 50% of people, superior to isthmus; persistent inferior end of thyroglossal duct

Thyroid hormones after week 11

Front 35

Formation of the face

7 steps

Back 35

Formation of the face

From mesenchyme derived from neural crest

Weeks 4-8

Stomodeum

Five primordia surrounding stomodeum

Nasal placodes and nasal pits – nostrils and nasal cavity

Primordial contributions to formation of face

Developmental changes and proportions

Front 36

Formation of the face

Stomodeum

Back 36

Formation of the face

Stomodeum

primitive mouth

anterior end of gut tube

buccopharyngeal membrane (prechordal plate)

Front 37

Formation of the face


Five primordia surrounding stomodeum

Back 37

Formation of the face

Five primordia surrounding stomodeum

frontonasal prominence – rostral (bridge of nose) boundary of stomodeum

paired maxillary prominences – lateral boundaries of stomodeum

paired mandibular prominences ( lower lip) – caudal boundary of stomodeum

Front 38

Formation of the face

Nasal placodes and nasal pits

Back 38

Formation of the face

Nasal placodes (will be the nostrils) and nasal pits – nostrils and nasal cavity

1. week five

2. ectodermal thickenings on ventrolateral part of frontonasal prominence

3. pits surrounded by medial and lateral nasal prominences

4. medial nasal prominences
pushed medially by developing maxillary prominences
fusion in midline forms intermaxillary segment
1. philtrum of upper lip
2. portion of maxilla with 4 incisor teeth
3. primary palate
4. tip of the nose

Front 39

Formation of the face

lateral nasal prominences

Back 39

lateral nasal prominences

separated from maxillary prominence by groove – nasolacrimal groove

will form nasolacrimal duct between eye and nasal cavity
(alae of nose)

Front 40

Primordial contributions to formation of face

1 Frontonasal prominence –
2 maxillary prominences –
3 mandibular prominences –

Back 40

Primordial contributions to formation of face

1 - Frontonasal prominence – forehead, bridge of nose,
a- medial and lateral nasal prominences medial nasal prominence – philtrum of upper lip, crest and tip of nose

b - lateral nasal prominence – alae of nose

2. maxillary prominences – cheeks, lateral part of upper lip

3. mandibular prominences – lower lip

Front 41

G. Developmental changes and proportions
1. early fetus
2. late fetal –
3. small face at birth

Back 41

G. Developmental changes and proportions

1. early fetus – flat nose, laterally placed eyes, mandibles underdeveloped
2. late fetal – eyes shift medially, forehead enlarges
3. small face at birth
a. jaws still small
b. unerupted teeth
c. small nasal cavities and maxillary sinus

Front 42

Oral cavity and nasal cavities
A. Intermaxillary segment

Back 42

Oral cavity and nasal cavities

A. Intermaxillary segment – from medial nasal prominence

1. Upper jaw – 4 incisors

2. Palatal – primary palate (week 6)

3. Rostral part of nasal septum joins portion from frontonasal prominence

Front 43

Oral cavity and nasal cavities

B. Secondary palate

Back 43

Oral cavity and nasal cavities

B. Secondary palate

1. Major part of definitive palate

2. Palatine shelves – lateral palatine processes; from maxillary prominence
a. week 6
b. lateral to tongue
c. week 7 ascend above tongue and fuse in midline
d. fuse anteriorly with primary palate
e. fuses superiorly with nasal septum

3. Incisive foramen – midline landmark separating primary and secondary palate

Front 44

Oral cavity and nasal cavities

C. Nasal cavities

Back 44

Oral cavity and nasal cavities

C. Nasal cavities

1. Nasal sacs within nasal pits separated from oral cavity by oronasal membrane

2. Rupture of oronasal membranes creates openings (primitive choanae) posterior to primary palate

3. Development of secondary palate shifts openings (definitive choanae) posteriorly

Front 45

Anomalies

A. Branchial fistulas -
B. First arch syndrome -
C. Third and fourth pouch syndrome
D. Ankyloglossia
F. Cleft lip and palate
E. Thyroglossal cyst/fistula

Back 45

Anomalies

A. Branchial fistulas - on the side
B. First arch syndrome - vulnerable to damage
C. Third and fourth pouch syndrome
D. Ankyloglossia - tongue-tie; extended frenulum- attachment of tongue on midline of floor mouth, speech, can't eat
F. Cleft lip and palate
E. Thyroglossal cyst/fistula - remnant of thyroglossal duct, near midline hyoid bone

Front 46

Anomalies
A. Branchial fistulas

Back 46

A. Branchial fistulas

B. First arch syndrome – failure of neural crest migration

1. Treacher Collins syndrome - lower half of the face, hard time eating
a. underdeveloped zygomatic bones
b. poorly developed mandible
c. lower eyelid defects
d. deformed external ear and sometimes middle and inner ear

2. Pierre Robin syndrome
a. hypoplasia of mandible
b. cleft palate - 2nd palate
c. eye and ear defects

Front 47

Anomalies

C. Third and fourth pouch syndrome

Back 47

C. Third and fourth pouch syndrome

1. DiGeorge sequence - pouch 3 & 4 pharyngeal pouch, glands do not developed correctly/ poorly
chromosome 22
a. hypoplasia of thymus and parathyroid glands

b. cardiac anomalies ( aortic arch anomalies, persistent truncus arteriosis
c. malformed mouth

immune system is uncompromise

Front 48

Anomalies

Third and fourth pouch syndrome

Back 48

Anomalies

Third and fourth pouch syndrome


1. DiGeorge sequence
a. hypoplasia of thymus and parathyroid glands
b. cardiac anomalies ( aortic arch anomalies, persistent truncus arteriosis
c. malformed mouth

Front 49

Eye
A. Optic vesicle

Back 49

Eye
A. Optic vesicle

1. Evaginates from forebrain in week 4

2. Induces surface ectoderm to form lens placode

3. Invaginates to form optic cup and choroid fissure

4. Posterior 4/5 optic cup (pars optica retinae) becomes retina
a. pigment layer
b. neural layer
c. intraretinal space

5. Anterior 1/5 optic cup (pars ceca retinae) becomes iris and ciliary body

6. Choroid fissure encloses hyaloid artery
a. artery becomes central artery of the retina
b. growing nerve fibers become optic nerve

Front 50

Lens placode

Back 50

Lens placode
1. Invaginates, loses contact with surface (week 5), forms lens vesicle
2. Formation of primary lens fibers from posterior wall fills lumen of vesicle

Front 51

C. Mesenchyme

Back 51

C. Mesenchyme
1. Choroid – vascular; continuous with pia mater of brain

2. Sclera – tough, fibrous; continuous with dura mater of brain

Front 52

E. Anomalies

Back 52

E. Anomalies
D. Cornea
1. Epithelial layer from surface ectoderm
2. Stromal layer continuous with sclera
3. Epithelial layer from mesenchyme

Front 53

E. Anomalies

Back 53

E. Anomalies
1. Coloboma iridis – choroid fissure fails to close in area where iris forms
2. Congenital cataracts – opaque lens; genetic, rebella infection
3. Microphthalmia – small eyeball; intrauterine cytomegalovirus or rubella infection; may by due to trisomy 13;

Front 54

VI. Ear
A. Inner ear

Back 54

VI. Ear
A. Inner ear

1. Otic placode – otic vesicle
a. week 4 placode – thickening of surface ectoderm
b. invaginates and forms otic vesicle

(1) dorsal portion – membranous labyrinth; utricle, semicircular ducts, endolymphatic duct
(2) ventral portion – saccule, cochlear duct; spiral organ of Corti in wall of cochlear duct for hearing

2. Mesenchyme surrounding vesicle
a. forms cartilagenous otic capsule
b. ossifies to form bony labyrinth of inner ear

Front 55

B. Middle ear

Back 55

B. Middle ear

1. Tubotympanic recess – pouch 1
a. tympanic cavity expands to surround ossicles
b. malleus and incus – arch 1
c. stapes – arch 2

Front 56

C. External ear

Back 56

C. External ear

1. External acoustic meatus – first pharyngeal cleft
a. meatal plug – proliferating epthelial cells fill space; disappear 7th month

2. Tympanic membrane – eardrum
a. ectodermal layer – cleft 1
b. endodermal layer – pouch 1
c. middle layer of connective tissue

3. Auricle – auricular hillocks
a. mesenchymal swellings – three from arch 1, three from arch 2
b. on each side of external acoustic meatus
c. shifted from neck to final location by development of mandible

Front 57

D. Anomalies
1. Congenital deafness

Back 57

D. Anomalies

1. Congenital deafness
a. may be due to abnormalities of inner or middle ear or both
b. rubella infection or genetic

2. auricular abnormalities – often associated with serious abnormalities such as trisomy 18 or trisomy 13

Front 58

Anomalies
Cleft lip and palate - 1st palate

Back 58

1. incisive foramen distinguishes b/t anterior n posterior clefts
2. may be unilateral or bilateral
3. anterior cleft
4. posterior clefts
5. combinations of anterior and posterior clefts

Front 59

Anomalies
Cleft lip and palate - 1primary palate

anterior clefts

Back 59

Anomalies
Cleft lip and palate - 1st palate

anterior clefts

a. cleft lip, cleft upper jaw, cleft b/t primary and secondary palate

b. partial or complete lack of fusion of maxillary prominence w/ medial nsal prominence

Front 60

Anomalies
Cleft lip and palate - 1st palate

posterior clefts

Back 60

Anomalies
Cleft lip and palate - 1st palate

posterior clefts

a. cleft secondary palate, cleft uvula

b. lack of fusion of palatine shelves - 2 palatine shelves don't fuse in midline

Front 61

Anomalies

Oblique facial cleft

Back 61

Anomalies

Oblique facial cleft

1. failure of maxillary prominence to fuse w/ lateral nasal prominnece

2. exposed nasolacrimal duct

Front 62

Anomalies

Median cleft lip

Back 62

Anomalies

Median cleft lip

1. failure of usion of medial nasal prominences

2. often accompanied by neural defects

Front 63

DIGESTIVE SYSTEM
I. Introduction

A. Primitive gut

Back 63

A. Primitive gut

1. tube of endoderm

2. formed during week four by lateral, cranial and caudal folding

Front 64

B. 4 Divisions

Back 64

1. pharynx -- from buccopharyngeal membrane to tracheobronchial diverticulum
2. foregut -- from pharynx to entrance of bile duct into duodenum
3. midgut -- from duodenum distal to entrance of the bile duct to proximal 2/3 of the transverse colon
4. hindgut -- distal 1/3 of the transverse colon to the cloacal membrane

Front 65

pharynx

Back 65

1. pharynx -- from buccopharyngeal membrane to tracheobronchial diverticulum

Front 66

Foregut

Back 66

2. foregut -- from pharynx to entrance of bile duct into duodenum(1st part)

Front 67

midgut

Back 67

3. midgut -- from duodenum distal to entrance of the bile duct to proximal 2/3 of the transverse colon

-rest of duodenum, all jejunum, cecum, ascending colon, 1st 2/3 of transver colon

Front 68

hingut

Back 68

4. hindgut -- distal 1/3 of the transverse colon to the cloacal membrane

Front 69

C. Germ layer sources

endoderm & splanchnic mesoderm

Back 69

C. Germ layer sources

1. endoderm -- epithelial lining and glands of mucosa; parenchyma of digestive glands

2. splanchnic mesoderm -- supporting structures including muscular walls and peritoneum

Front 70

D. Arterial supply
foregut, midgut, hindgut

Back 70

D. Arterial supply

1. foregut -- celiac artery
2. midgut -- superior mesenteric artery
3. hindgut -- inferior mesenteric artery

Front 71

II. Foregut -- contains?

Back 71

II. Foregut -- esophagus, stomach, duodenum, liver, gall bladder, and pancreas

Front 72

A. Esophagus

Back 72

A. Esophagus

1. esophagotracheal septum -- separates digestive and respiratory tubes
2. lengthens as heart and lungs descend
3. muscular coat from mesoderm
a) upper 2/3 striated
b) lower 1/3 smooth

Front 73

A. Esophagus

4. anomalies

Back 73

A. Esophagus
4. anomalies

a) atresia -- proximal portion ends in blind sac
b) esophagotracheal fistula -- distal portion connected to trachea
c) a and b result in polyhydramnios

Front 74

B. Stomach

Back 74

B. Stomach

1. dilation of foregut during week 4
2. rotations
a) longitudinal axis 90o clockwise; original dorsal side of tube now on left
b) anterior-posterior axis clockwise so original dorsal side now inferior and forms greater curvature

Front 75

B. Stomach

3. anomalies

Back 75

B. Stomach
3. anomalies

a) pyloric stenosis -- narrowing of pyloric lumen
(1) hypertrophy of muscle layer
(2) obstructs passage of food
(3) projectile vomiting after feeding

Front 76

C. Duodenum

Back 76

C. Duodenum

1. formed by foregut (proximal to entrance of the bile duct) and midgut

2. C-shape caused by rotation of stomach

3. lumen obliterated during second month and then recanalized

Front 77

D. Liver

Back 77

D. Liver

1. liver bud from proliferating endoderm during week three

2. penetrates septum transversum (mesodermal plate between pericardial cavity and stalk of yolk sac) and expands

3. connection to foregut forms bile duct

4. ventral outgrowth of bile duct forms gall bladder and cystic duct

5. hepatic sinusoids -- from vitelline veins

6. connective tissue, Kupffer cells, and hematopoietic cells from mesoderm

7. functions

a) hematopoiesis during most of uterine life
b) bile production beginning about week 12

Front 78

E. Mesenteries

Back 78

E. Mesenteries

1. dorsal mesogastrium

a) greater omentum

b) attached to greater curvature of stomach (originally dorsal)

2. ventral mesogastrium

a) derived from septum transversum

b) divided by developing liver into two parts

(1) lesser omentum -- between liver and stomach

(2) falciform ligament --between liver and ventral body wall

Front 79

A. Pancreas

Back 79

A. Pancreas

1. two buds of endoderm in region of the duodenum
2. by rotation of the duodenum the ventral bud comes to lie below and behind the dorsal bud
3. ventral bud
4. dorsal bud
5. islets of Langerhans appear during month three; insulin secretion during month five
6. anomalies

Front 80

A. Pancreas
1. two buds

Back 80

A. Pancreas
1. two buds of endoderm in region of the duodenum

a) dorsal bud in dorsal mesentery; attached to duodenum via duct of Santorini

b) ventral bud close to bile duct; attached to duodenum via duct of Wirsung

Front 81

A. Pancreas

3. ventral bud

Back 81

A. Pancreas

3. ventral bud
a) uncinate process
b) inferior part of head of the pancreas
c) proximal part of main pancreatic duct (of Wirsung)

Front 82

A. Pancreas
4. dorsal bud

Back 82

4. dorsal bud

a) major portion of gland
b) distal portion of main pancreatic duct (of Wirsung)
c) dorsal duct may persist as accessory pancreatic duct

Front 83

A. Pancreas

Back 83

A. Pancreas


6. anomalies

a) annular pancreas -- ventral pancreatic bud encircles duodenum and may constrict or obstruct it
b) accessory pancreatic tissue -- most commonly found in stomach or Meckel's diverticulum

Front 84

III. Midgut
A. Review

Back 84

III. Midgut
A. Review

1. communicates with yolk sac via vitelline duct

2. supplied by superior mesenteric artery

3. in adult extends from junction of bile duct with duodenum to distal 1/3 of transverse colon

Front 85

III. Midgut
B. Primary intestinal loop

Back 85

B. Primary intestinal loop -- from rapid elongation of gut tube
1. cephalic limb -- distal duodenum, jejunum, proximal part of ileum
2. caudal limb -- distal ileum, cecum, appendix, ascending colon, and proximal 2/3 of transverse colon

Front 86

III. Midgut

C. Physiological herniation and rotation

Back 86

C. Physiological herniation and rotation

1. during week six due to rapid growth especially of cephalic limb
2. midgut occupies extraembryonic coelom in umbilical cord
3. rotation 270o counterclockwise around axis of superior mesenteric artery accompanied by further elongation and coiling
4. retraction begins during week 10
a) jejunum first to reenter abdomen
b) cecal bud (gives rise to cecum and appendix) last to reenter abdomen

Front 87

III. Midgut
4. retraction begins during week 10

Back 87

4. retraction begins during week 10

a) jejunum first to reenter abdomen
b) cecal bud (gives rise to cecum and appendix) last to reenter abdomen

Front 88

I. Hindgut
A. Derivatives
B. Cloaca
C. Proctodeum -- anal pit

Back 88

I. Hindgut
A. Derivatives

1. distal 1/3 transverse colon
2. descending colon
3. sigmoid colon
4. rectum
5. proximal portion of anal canal
6. internal lining of bladder and urethra

Front 89

I. Hindgut

B. Cloaca --

Back 89

B. Cloaca -- endoderm lined cavity in contact with surface ectoderm at cloacal membrane
1. terminal portion of hindgut
2. divided by urorectal septum into primitive urogenital sinus and anorectal canal at ~week 7
3. cloacal membrane divided into urogenital membrane and anal membrane

Front 90

I. Hindgut

C. Proctodeum -- anal pit

Back 90

C. Proctodeum -- anal pit

1. ectodermal depression
2. separated from anorectal canal by anal membrane
3. when membrane ruptures, completes canal to surface
a) pectinate line
b) upper part of anal canal lined by endoderm (hindgut) of columnar epithelium
c) lower part lined by ectoderm (proctodeum) of stratified squamous epithelium

Front 91

I. Anomalies of midgut and hindgut


A. Meckel's diverticulum
B. Vitelline duct
1. cyst -- ends close but middle portion is intact
C. Omphalocele
D. Gastroschisis
E. Abnormal rotations
F. Atresia and stenosis
G. Rectal atresia
H. Congenital megacolon (Hirschsprung's disease)

Back 91

A. Meckel's diverticulum
B. Vitelline duct
1. cyst -- ends close but middle portion is intact
C. Omphalocele
D. Gastroschisis
E. Abnormal rotations
F. Atresia and stenosis
G. Rectal atresia
H. Congenital megacolon (Hirschsprung's disease)

Front 92

A. Meckel's diverticulum

Back 92

A. Meckel's diverticulum

1. persistent portion of vitelline duct
2. may contain heterotopic pancreatic tissue or gastric mucosa

Front 93

B. Vitelline duct

Back 93

B. Vitelline duct

1. fistula -- patent duct through entire length
2. cyst -- ends close but middle portion is intact

Front 94

C. Omphalocele

Back 94

C. Omphalocele

1. herniation of viscera in umbilical ring
2. caused by failure of retraction of intestinal loops from physiological herniation

Front 95

D. Gastroschisis

Back 95

D. Gastroschisis

1. defect in ventral body wall
2. herniation of abdominal contents into amniotic cavity
3. not covered by peritoneum or amnion

Front 96

E. Abnormal rotations

Back 96

E. Abnormal rotations

1. danger of vascular or loop obstruction
2. rotate only 90o -- colon and cecum retract first and lie on left side
3. reversed rotation 90o clockwise -- transverse colon passes behind duodenum

Front 97

F. Atresia and stenosis

Back 97

F. Atresia and stenosis

1. most common in duodenum and ileum
2. due to failure of recanalization or vascular failure

Front 98

G. Rectal atresia

Back 98

G. Rectal atresia

1. incomplete formation of hindgut
2. imperforate anus

Front 99

H. Congenital megacolon (Hirschsprung's disease)

Back 99

H. Congenital megacolon (Hirschsprung's disease)

1. usually associated with neural anomalies -- absence of parasympathetic ganglia
2. usually involves rectum and sigmoid colon