SM01 Mini3 Flashcards
1
Q
primary cardiogenic field
A
horse-shoe shaped zone of heart precursor cells of splanchnic mesoderm (subdivision of lateral plate mesoderm) cranially & laterally to neural plate (if it were on the mesoderm, but it’s really on the ectoderm above)
W3
2
Q
heart tube
A
two endothelial lined tubes left & right that fuse lateral body folding
W3
3
Q
definitive heart tube
A
single heart tube after fusion of earlier endothelial tubes (through apoptosis of medial cells)
they do NOT fuse at the cranial or caudal extremes
created after lateral body folding, begins cranially and continues caudally
W3
4
Q
cranio-caudal folding effect on heart
A
repositions heart tube into presumptive thoracic cavity, caudal to brain & oral cavity
5
Q
primitive heart tube layers
A
- inner: endocardial layer
- middle: cardiac jelly
- outer: myocardial layer (muscle)
D22-25 (W4), presence of heart beat
6
Q
epicardium is derived from
A
mesodermal cell that migrate from near the developing liver
7
Q
cardiac jelly
A
extracellular matrix proteins
unknown function, but required, b/c if it doesn’t form, a spontaneous abortion will occur
middle layer of primitive heart tube
8
Q
vitelline veins
A
paired right & left veins that carry deoxygenated blood from the yolk sac to caudal end of primitive heart tube
9
Q
cardinal veins
A
paired right & left veins that carry deoxygenated blood from body of embryo to caudal end of primitive heart tube
10
Q
umbilical veins
A
paired left & right veins that carry oxygenated body from placenta to the caudal end of primitve heart tube
11
Q
primitive heart outflow tract
A
truncus arteriosus (which becomes the aorta & pulmonary thrunk) connects to right & left aortic archs (3 branches/side at this stage)
12
Q
transverse pericardial sinus
A
forms from the degeneration of dorsal mesocardium
postnatally: located posteriorly to aorta and pulmonary trunk & anterior to superior vena cava
13
Q
dorsal mesocardium
A
initial attachment of heart to posterior thoarcic wall during the development of pericardial cavity
14
Q
5 dilations of primitive heart tube cranial to caudal
A
- truncus arteriosus
- bulbus cordis
- primitive ventricle
- primitive artrium
- right & left horns of sinus venosus
blood flows caudally to cranially
15
Q
heart tube folding
A
D23 too long to be accomodated in available space
caudal primitive atrium shifts back then up & to the left, dorsocranially & left
cranial primitive ventricle moves ventrocaudally & to the right
D25-28 (end of W4)
blubus cordis & truncus arteriosus are medial & anterior in resulting structure
16
Q
dextrocardia
A
when heart is on right instead of left due to abnormal looping
w/situs inversus→ normal or asymptomatic life
in isolation→ accompanied by severe cardiac abnormalities, ex. single ventricle or ventricular septal defect
17
Q
formation of right atrium
A
trabeculated part: from right side of primitive atrium
sinus venarum (smooth portion): from right horn of sinus venosus
18
Q
sinus venarum
A
smooth part of right atrium on posterior wall near opening of superior vena cava
19
Q
left horn of sinus venosus derivatives
A
oblique vein of the left atrium & coronary sinus
20
Q
crista terminalis
A
internal ridge demarcating the juntion of smooth portion & trabeculated portion of atria
21
Q
formation of left atrium
A
trabeculated portion: left side of primitive atrium
smooth portion: from reincorporated pulmonary vein
single pulmonary vein develops out of posterior wall of left atria→ branches into four & connect to lungs→ proximal portions reincorporate into left atria forming smooth portion of left atria
22
Q
3 fetal shunt systems
A
open prenatally, close postnatally
- ductus venosus (to liver)
- foramen ovale (between atria)
- ductus arteriosus (to lungs)
23
Q
circulation through fetal system
A
placenta→ umbilical vein→ ductus venosus→ inferior vena cava→ right atria (also receives from superior vena cava)→ right ventricle & thru foramen ovale to left atria (also receives from pulmonary veins)→ left ventricle→ aortic arch & pulmonary trunk (to aortic arch via ductus arteriosus)→ descending aorta→ internal iliac arteries→ umbilical arteries→ placenta
24
Q
septum primum
A
thin membranous septum starts at superior medial wall of primitive atrium & grows toward the endocardial cushion
as it nears the endocardial cushion, apoptosis occurs in some superior central cells opening the ostium secudum to keep the shunt system in place
25
ostium primum
opening between growing septum primum & endocardial cushion
allow shunting of blood from right to left atria
26
ostium secundum
opening of septum primum in superior central portion
allow shunting of blood from right to left atria
27
endocardial cushions
form in atrioventricular region
dorsal & ventral fuse to partition AV region into left & right canals
28
septum secundum
thick muscular septum
grows cranial to caudally like septum secundum and just to its right
past ostium secundum, it grows outward a little bit to leave an opening creating the foramen ovales
29
foramen ovale
opening in caudal portion of septum secundum
prenatally: allows oxygenated blood to bypass lungs to left atrium
postnatally: higher pressure in left atrium prevents backflow of blood into right atrium & septum primum adheres to septum secundum
30
valve of foramen ovale
higher pressure in right atrium v. left atrium pushes septum primum into left atrium, acting as a primitive valve to foramen ovale shunt system
31
types of atrial septal defects
10% of congenital heart defects
females more frequent than males
1. probe patent foramen ovale
2. ostium secunudum defect
3. endocardial cushion defect w/ostium primum defect
4. sinus venosus defect
5. common atria
32
probe patent foramen ovale
failure of septum primum to adhere to septum secundum after birth
usually small & insignificant
increased risk of migraine
25% of all people
33
ostium secundum defects
1. reabsorption of septum primum in abnormal location
2. excessive reabsorption of septum primum
3. defect development of septum secundum
4. combination of excessive reabsorption of septum primum & large foramen ovale
34
endocardial cushion defect w/ostium primum defect
septum primum doesn't fuse w/endocardial cushions→ patent ostium primum
septum secundum never reaches EC either
associated w/mitral valve cleft
35
mitral valve cleft
slit-like or elongated hole usually involving anterior leaflet
36
sinus venosus defect
occurs in septum near superior vena cava
causes: incomplete absorption of sinus venosus into right atrium or abnormal development of septum secundum
consequences: pulmonary veins may be attached to right atrium instead of left
requires surgical repair
37
common atrium
aka cor tricolare biventriculare
three chambered heart= one atrium, two ventricles
very rare
failure to develop septum primum or septum secundum
associated w/heterotaxy (abnormal distribution of organs in the thorax & abdomen)
38
results of premature closure of foramen ovale
hypertrophy of right heart
under-development of left heart
death shortly after birth
39
derivatives of truncus arteriosus
proximal aorta & pulmonary trunk
40
derivatives of bulbus cordis
caudally: smooth right ventricle & smooth left ventricle
cranially: (aka conus cordis) proximal aorta & pulmonary trunk w/truncus arteriosus
41
derivatives of primitive ventricle
trabeculated portions of left & right ventricles
42
derivatives of primitive atria
trabeculated portions of left & right atria
43
derivatives of sinus venosus
right: smooth part of right atrium (sinus venarum)
left: coronary sinus & oblique vein of left atrium
44
interventricular spectum formation
not as complex as atrial→ don't need shunting→ complete before birth
muscular & membranous components that fuse
45
formation of muscular interventricular septum
grows from expanding myocardium of ventricles (end of W4) toward endothelial cushions
stops at W7 before fusion with endothelial cushions, creating interventricular foramen
46
interventricular foramen
opening of the ventricular septum formed W7 when the muscular interventricular septum does not fuse with the endothelial cushions
47
Membranous interventricular septum
forms from right endothelial cushions extension toward muscular interventricular septum & tissue from teh airticopulmonary septum growing down from the outflow tract
48
ventricular spectal defects
most close spontaneously during the first year of life
more frequent in females than males
membranous: most prevalent & often associated with aorticopulmonary septal defects
muscular: single or swiss chesse defects & can fill spontaneously
cor triloculare biatriatum/common ventricle
49
partitioning of outflow tract
neural crest cells migrate & invade truncal (on truncus arteriosus) & bulbar (on conus cordis-cranial remenant of bulbus cordis) ridges→ grow & twist in sprial fashion→ fuse to form aorticopulmonary septum
50
aorticopulmonary septum
derived from neural crest cells
partitions the outflow tract to form aorta (ventral &sac) & pulmonary trunk
51
aortic sac
derived from truncus arteriosus
formed by aorticopulmonary septum
gives rise to right & left horns→ brachiocephalic artery, ascending aorta & proximal segment of aortic arch
52
persistent truncus arteriosus
always seen w/ventricular septal defect
failure of truncus arteriosus to partition→ common outflow from both ventricles→ oartially deoxygenated blood circulates (cyanosis)→ death in first 2 years
53
transposition of great vessels
caused by aorticopulmonary partition not spiraling when formed→ pulmonary arteries connect to left ventricle & aorta connects to right ventricle→ oxygenated blood goes back to lungs & blood from body goes around again w/o getting oxygenated
3:1 males to females
risk factors: intrauterine rubella & other viral illnesses
cyanosis in 2/3 day postnatal
incompatible w/life unless shunt system still available
treatment: prostagladin to keep ductus arteriosus open
54
tetralogy of Fallot
displacement of septum due to four defects:
1. pulmonary stenosis (narrosing of blood vessel)
2. membranous interventricular septal defect
3. overriding aorta (displacement to the right)
4. right ventricular hypertrophy (from working harder to get blood through stenosed pulmonary artery)
less blood reaches lungs, poor oxygenation of body, cyanosis
can be corrected surgically
55
lung bud formation
aka repsiratory diverticulum
W4- appears D22 & grows ventrocaudally
outcropping of endoderm from foregut
surrounding splanchnic mesoderm will form the connective tissue & musculature of the lungs
separates from esophagus by tracheo-esophageal ridges
56
tracheo-esophageal ridge
separates esophagus dorsally & trachea and lung buds ventrally
57
tracheo-esophageal fistulas
TEF
more common in males
most associated with esophageal atresia
cause: incomplete division of foregut into esophageal & respiratory portions
can cause polyhydraminos
NOT usually isolated congenital abnormality
58
tracheo-esophageal fistula w/esophageal atresia
upper portion of esophagus ends & lower portion branches off of posterior trachea (fistula- abnormal or surgical passage)
rapid abdomen distention- air in stomach
aspiration of food (milk) into lungs or ejected
59
tracheo-esophageal fistula between trachea & esophagus
aka H-type
connecting tube from esophagus to posterior traches
4% of cases
food (milk) may be driven into lungs
60
VACTERL syndrome
**V**ertebrate defects
**A**nal atresia
**C**ardiac defects
**T**racheo-esophageal fistulas
**E**sophageal atresia
**R**enal abnormalities
**L**imb defects
61
VATER syndrome
**V**ertebrate defects
**A**nal atresia
**T**racheo-esophageal fistulas
**E**sophageal atresia
**R**enal abnormalities
62
W5 lung formation features
formation of left & right lung buds during partitioning by tracheo-esophageal ridge
main & secondary bronchi (3 on tight & 2 on left)
right is straighter (more vertical) & has larger lumen than left→ more foreign objects get lodged in it
63
formation of vasculature
W3
sets of paired vessels
arteries: aortic arches, dorsal aorta, vitelline & umbilical arteries
veins: cardinal, vitelline, & umbilical veins
64
when vascular connection is made between placenta & embryo
W4
65
where blood vessels begin
embryo & yolk sac
66
Aortic arches
five paired arteries (L+R): 1, 2, 3, 4, 6 (cranial to caudal)
5's only purpose is to kickstart the growth of 6 & degenerate
dorsally connect to dorsal aortae
67
descending aorta formation
fusion of right & left dorsal aorta at T4-L4
68
adult derivative of first aortic arch
mostly degenerates
remenants: maxillary arteries
69
adult derivatives of second aortic arch
most degenerates
dorsal end forms hyoid artery which later forms the stapedial arteries, which is a transient connect between external & internal carotid arteries
70
persistent stapedial artery
manifests as pulsatile mass in middle ear cavity
sometimes causes pulsatile tinnitus
71
adult derivatives of third aortic arch
right & left common carotid arteries
proximal portion of internal carotid branches
72
adult derivatives of fourth aortic arch
left: arch of aorta
right: proximal right subclavian artery
73
formation of right subclavian artery
proximally: fourth aortic arch
distally: 7th intersegmental artery
74
adult derivatives of sixth aortic arch
right: right pulmonary artery & grows toward lungs
left: forms ductus arteriosus (part of shunt system)→ closes after birth & becomes ligamentum arteriosum
75
recurrent laryngeal nerves
branch off of vagus nerves (runs anterior to arches & just medial to R subclavian & descendin aorta on L)
R: loops under & posterior to 4th aortic arch
L: loops under & posterior to 6th aortic arch (ductus arteriosus)
innervates larynx
76
coarctation of aorta
constriction or narrowing of aorta
subdivided by location: pre or postductal
77
postductal coarctations of aorta
restriction occurs below ductus arteriosus
w/ & w/o ductus arteriosus closure, most are closed
most common type of coarctation
collateral circulation thru: subclavian arteries→ internal thoracic→ anterior intercostal arteries→ posterior intercostal arteries (3rd-9th)→ thoracic aorta
dilated tortuous arteries: increased blood flow & palpable pulses (in posterior intercostal spaces)→ rib notching
blood pressure is lower in lower body & lower limbs & higher in upper limbs
78
preductal coarctation of aorta
restriction of aorta before the ductus arteriosus
w/ & w/o patent ductus arteriosus
patent ductus arteriosus allows blood flow to inferior body, but is deoxygenated
collateral circulation through subclavian arteries does NOT work, reason unknown
79
double aortic arch
persistent portion of right dorsal aorta cranial to T4
results in vascular ring that can constrict the esophagus & trachea or be asymptomatic
80
vitelline arteries
paired (R+L) vessels of yolk sac where they anastamose in a vascular plexus→ migrate into embryo as yolk sac regresses→ separate from descending aorta→ reattaches to descending aorta as 3 trunks
celiac, superior & inferior mesenteric arteries
81
celiac trunk
found at T12
supplies forgut structures (liver & spleen)
82
superior mesenteric trunk
found at L1
supplies mudgut structures
83
inferior mesenteric trunk
found at L3
supplies inferior mesenteric structures
84
umbilical arteries
carry deoxygenated blood & waste from fetus to placenta
initially connectes to dorsal aortae in sacrum→ loose connection (W5)→ connect to proximal segment of internal iliac arteries
thus proximal portion of umbilical arteries form distal segment of internal iliac arteries & superior vesicle arteries; distal degenerates
close a few minutes after birth do to smooth muscle contraction in vessel walls
perment fibrous closure in 2-3 months
85
vitelline veins
drain blood from yolk sac to heart
initially a pair that drain into sinus horns
cranial L: left hepatocardiac channel→ regresses w/left sinus horn, leaving the left hepatic vein caudally
cranial R: right hepatocardiac channel→ hepatic portion of inferior vena cava & right hepatic vein
central R+L: hepatic sinusoids & ductus venosus (venous plexus in liver)
caudal portions of both: form plexus around duodenum→ portal vein (connects hepatic sinusoids in liver & passes thru septum transversum) & splenic, superior mesenteric, and inferior mesenteric veins
86
umibilical veins
returns oxygenated blood from placenta to embryo
R: completely obliterated in 2nd month
L: known as definitive umbilical vein, drains into ductus venosus then inferior vena cava
after birth: intraabdominal portion becomes ligamentum teres hepatic or round ligament of the liver
87
common cardinal veins
drains blood from body to heart of embryo
receives drainage from anterior & posterior cardinal veins
88
ductus venosus
fetal shunt to bypass liver sinusoids prenatally
shunt connects hepatocardiac channel w/left umbilical vein
adult derivative: ligamentum venosum
89
left brachiocephalic vein formation
W8
develops form anastomoses of L+R anterior cardinal veins, when caudal left anterior cardinal vein degenerates
functions to shunt systemic blood from L to R
90
posterior cardinal veins
important for drainage of mesonephroi
majority degenerate
remaining portion forms Root of azygos vein (Right posterior cardinal vein) & common iliac veins
91
supracardinal veins
formed during late embryonic period to take over the role of posterior cardinal artery
disrupted in the region of the kidneys
92
subcardinal veins
formed during late embryonic period to take over the role of posterior cardinal artery
anastamose with supracardinal veins to for azygos & hemiazygos veins
93
pseudoglandular period
W5-17
formation of lung division thru terminal bronchioles, but not including respiratory bronchioles
repiration not yet possible
94
canalicular period
W16-25 (28)
terminal bronchioles give rise to repiratory bronchioles
alveolar ducts form
mesodermal tissue becomes highly vascularized
low chance of survival, but respiration is possible toward the end
95
terminal sac period
W24-birth
terminal sacs develop & surfactant produced
epithelium thins & capillaries come into contact forming blood-air barrier
96
alveolar period
birth to 8yrs-old
increasing number of alveoli & respiratory bronchioles
95% formed during this period
97
type I pneumocytes
differentiates from epithelium
cells across which gaseous exchange takes place
98
type II pnuemocytes
differentiates from epithelium
secretes surfactant, forms filmover internal wall of terminal sacs to decrease surface tension to facilitate inflation
99
atelectasis
partial or complete collapse of lung
100
Respiratory distress syndrome
prime cause: premature birth (W23-30)
signs: labored breathing, increased RR, mechanical ventilation needed, damage to alveolar lining (fluid & serum proteins leak into alveolus), & continued injury may lead to detachment of alveolar lining (causing hyaline membrane dz)
treat w/glucocorticoid to accelerate fetal lung development and surfactant production & artifical surfactant therapy
101
surfactant B deficiency
causes respiratory distress syndrome
autosomal recessive inheritance pattern
fatal dz
NO treatment
102
unilateral pulmonary agenesis
failure of one lung to develop
presentation: repiratory distress in 1st year, usually w/lower respiratory tract infection
60% have concurrent congenital abnormalities: cardiac lesions, diaphragmatic hernias, & skeletal anomalies (vetebral or costal)
higher frequency of anomallies seen with R lung agenesis
103
bilateral pulmonary agenesis
absence of lungs
extremely rare & always lethal
104
pulmonary hypoplasia
failure to obtain adequate size, but has all components
severity determines amt of compromise
may be associated w/congenital diaphragmatic hernia (abdominal organs in thorax via whole in diaphragm)
105
congenital cysts of lung
formed by dilation of terminal or larger bronchi
usually drain poorly causing frequent infections
106
diaphragm formation
divides thoracic & abdominal cavities
from: septum transversum, pleuroperitoneal membranes, dorsal mesentary of esophagus, & muscular ingrowth of somites at cervical levels C3-C5
107
septum transverseum
derived from mesoderm
begins to divide intraembryonic cavity into thoracic & abdominal cavities
pericardial canals: open channels left on either side from incomplete formation of septum trnasversum (the lungs grow in these)
108
congenital diaphragmatic hernia
1/2,000 births
when pleuroperitoneal folds fail to form properly, more often on L (called foramen of Bochdalek
results: small bowel enters thorax→ hinders pulmonary formation causing pulmonary hypoplasia
degree determines severity
can be surgically repaired
109
formation of IVC
Inferior vena cava
1. hepatic: derived from hepatocardiac channel (from right vitelline vein)
2. prerenal (suprarenal): derived from right subcardinal vein
3. renal: derived from supracardinal anastomoses of right subcardinal vein
4. postrenal (infrarenal): derived form right supracardinal vein
110
absence of inferior vena cava
failure of hepatic segment formation, et al form attachesd to azygos
blood will drain via azygos & hemizygos veins
usually associated w/heart malformations
111
double IVC
inferior portion of left supracardinal vein persists
left IVC typically ends at left renal vein, cross aorta, & joins R IVC
no complications
112
SVC formation
from an anastomoses of right common cardinal vein & right anterior cardinal vein
113
double SVC
cause: persistence of left anteriof cardinal vein & failure of left brachiocephalic to form
results: left SVC drains venous blood from left & drains into coronary sinus, which dilates to accommodate increased blood flow
no ill effects
114
left SVC in isolation
cause: failure of degeneration of left anterior cardinal vein→ anastomoses of left common cardinal vein & left anterior cardinal vein→ L SCV formation AND degeneration of right common cardinal & caudal portion of right anterior cardinal veins
no left brachiocephalic vein formed
results: blood drains to L SVC→ coronary sinus→ right atrium
115
left brachiocephalic formation
from anastomoses of left & right anterior cardinal veins
when caudal part of left anterior cardinal vein degenerates
116
changes in circulation after birth
* alveoli expand
* pulmonary vessels open & resistance reduces
* placental blood flow ceases
* above events initiate closure of shunts
* high oxygen saturated blood enters ductus arteriosus→ increase in localized O2 tension→ constriction of ductus arteriosus
* immediately after birth
* complete obliteration intima in 1-3 months
* foramen ovale closure due to pressure changes in atria
* fusion (permenant closure) takes about 1yr
117
patent ductus arteriosus
most common among preterm babies
can close spontaneously
treatment: in preterm, use of NSIDS or indomethacin to help close by blocking prostagladin E1 (which is keeping it open)→ will NOT work in full term babies or adults
118
formation of primitive gut tube
creeated by lateral folding in W3+4
all 3 layers in concentric tubes around lume
119
foregut
cranial portion of primitve gut tube
blood supply: celiac trunk @ T12
120
midgut
portion of primitive ut tube attached to the yolk sac
blood supply: superior mesenteric @ L1
121
hindgut
caudal portion of primitive gut tube
blood supply: inferior mesenteric @ L3
122
vitelline duct
opening/passageway from midgut to yolk sac
123
formation of vitelline duct
end of W4
constriction of midgut connection to yolk sac as craniocaudal folding takes place
incorporated into proximal umbilical cord
\*formed at the same time as allantois\*
124
ileal diverticulum
aka Meckel's diverticulum
persistence of vitelline duct postnatally
may become inflammed & mimic appendicitis
2% pop
2" length
w/in 2' of ileocecal valve
found under age of 2
males 2x over females
(other persistence of vitelline duct: enterocyst or vitelline fistula)
125
derivatives of foregut
pharynx, esophagus, stomach, superior 1/2 of duodenum
126
derivatives of midgut
inferior 1/2 of duodenum, jejunum, ileum, cecum, ascending colon, R 2/3 transverse colon
127
derivatives of hindgut
L 1/3 transverse colon, descending colon, sigmoid colon, rectum, & upper portion of anal canal
128
stomodeum
mouth opening created by the rupture of the buccopharyngeal (oropharyngeal) membrane
W4
129
cloacal membrane rupture
W7
creats opening for anus & urethra
130
layers of gut tube
lumen outward
1. mucosa (epithelium [**endodermic origin**], lamina propria, & muscularis mucosae)
2. submucosa
3. muscularis
4. serosa/adventitia
derived from splanchnic mesoderm
131
formation of esophagus
W3 w/formation of esphagotracheal septum
cranially: pharynx
caudally: esophagus
W4-7: elongation
histological changes: simple columnar→ stratified columnar→ multilayered ciliated→ straified squamous non-kartinated epithelium
132
short esophagus
cause: failure to elongate in proportion to neck & thorax development
result: congenital hiatal hernia (part of stomach displaced into thorax)
133
esophageal stenosis
caused: incomplete recanalization of lumen
134
Barret's Esophagus
CELLO (columnar epithelium lined lower oesophagus)
* congenital: cells did not complete histological evolution→ tendency toward GERD
* acquired: abnormal change in cells, possibly caused by chronic acid exposure or reflux esophagitis
* premalignant condition
* 1-5% develop cancer
135
formation of stomach
end of W4/beginning W5, fusiform dilation of foregut
attached to anterior & posterior walls via ventral & dorsal mesentery respectively
dorsal grows more to create greater curvature
L+R vagus nerve run on either side
makes 90º turn counter-clockwise: greater curvature is L, lesser curvature is R, R vagus n. becomes posterior vagus n., L vagus n. becomes anterior vagus n., & dorsal mesentery is L as greater omentum
anteropsterior axis rotation: pyloris up & cephalic portion down
136
histologenesis of stomach
rugae & gastic pits of epithelium form during late embryonic period
cell differentiation during early fetal period
HCl production just before birth
137
congenital pyloric stenosis
cause: incomplete recanalization of pyloric lumen during development
symptoms: projectile vomitting during 2nd week, formation of pyloric mass, infrequent stool, dehydration & loss of subcutaneous fat
male 4x more than female
1:200 live births
Tx: surgery
138
derivatives of embryonic ventral mesentery
lesser omentum (hepatoduodenal & hepatogastric ligaments), falciform ligament of liver, coronary ligament of liver, & triangular ligament of liver
139
derivatives of embryonic dorsal mesentery
greater omentum (gastrorenal, gastrosplenic, gastrocolic, & splenorenal ligaments), mesentery of small intestine, mesoappendix, transverse mesocolon, & sigmoid mesocolon
140
Formation of omental bursa
aka lesser peritoneal sac
space behind stomach formed when the dorsal mesogastrium is pulled to the L during longitudinal rotation
141
Greater Sac
peritoneal cavity opening on left & anterior of stomach & mesentery after longitudinal rotation
142
epiploic foramen of Winslow
opening if the lesser omentum (between stomach & liver) connection the greater & lesser sacs
143
formation of greater omentum
dorsal mesogastrium extends to forma double layer sac over small intestine & transverse colon
2 layers fuse to form greater omentum, hanging from greater curvature of the stomach to protect the small intestine & transverse colon
144
formation of the duodenum
derivative of foregut & midgut
duodenum & head of pancreas are pressed dorsally aginst body wall after stomach rotation (retroperitoneal)
dorsal mesoduodenum fuses w/peritoneum
145
lesser omentum is formed from
ventral mesogastrium
146
development of midgut
expands to U-shpaed midgut loop in W5
cranial limb→ distal duodenum, jejunum, & upper ileum
caudal limb→ rest of ileum & rest of midgut
rapid growth of liver→ forces physiological herniation of midgut into umbilical cord in W6 & rotates 90º counterclockwise around superior mesenteric artery→ W10 abd expansion allows return to abd cavity→ +180º counter-clockwise rotation during regression & \*\*viteline duct looses connection to intestines\*→ mesenteries of ascending & descending colon fixed to peritoneum of posterior wall (retroperitoneal)
147
histological development of small intestine
M2, epithelium proliferates to obliterate lumen→ recanalization as multi-layered epithelium→ rearrangement of tissue to yield villi & crypts w/stem cells (simple columnar epitelium)
cell types formed by end of 2nd trimester (M6)
148
omphalocoele
failure of intestinal loop to return to abd cavity following physiological herniation
seen by fetal US
variation in size
has shiny coverings
frequently associated w/: fetal liver herniation w/small abd size & pulmonary hypoplasia (small lungs)
other risks: other birth defects, intestinal malrotation, & urinary anomalies
tx: bag covering & slowly push intestines inside until abd defect can be sewn shut, takes time
149
gastrochisis
aka cleft stomach
no shiny covering, but otherwise looks similar to omphalocoele (but rarer)
no known cause
1: 3000 births
tx: bag covering & slowly push intestines inside until abd defect can be sewn shut, takes time
150
congenital umbilical hernia
more common in premature births
2x male over female
intestines return to abd cavity, but ventral abd wall doesn't close umbilical ring
protruding bowel still covered by skin
some resolve spontaneously by 2yrs-old
sx by 4yrs-old if symptomatic
151
non-rotation of midgut
results in small intestine on R & large intestine on L
usually asymptomatic
152
Mixed rotation of midgut
failure to complete last 90º rotation
results in cecum inferior to pylorus fixed to posterior abd wall by peritoneal bands
153
volvulus
twisting of intestines
impedes intestinal contents & compromises blood supply
154
cloaca
endodermal lined pouch at terminal end of hindgut
partitioned by urorectal septum into rectum, upper anal canal, & urogenital sinus
155
proctoderm
surface ectoderm
joined with cloaca to form cloacal membrane
156
cloacal membrane
joining of proctoderm & cloaca
partitioned to form anal membrane & urogenital membrane
157
perineal body
where urorectal septum fused with cloacal membrane
158
development of anal canal
upper: from hindgut
lower: from proctoderm
pectinate line marks the junction of upper & lower ana canals (site of former anal membrane)
159
intestinal stenosis
narrowed intestinal lumen from incomplete recanalization
causes considerable backup→ excessive GI distention & excessive vomitting
160
intestinal atresia
complete failure of recanalization
most commonly found in the duodenum
causes considerable backup→ excessive GI distention & excessive vomitting
161
duplication of intestines
rare congenital maleformation
dual wall formation
caused by abnormal recanalization
162
Meconium
dark green substance that is 1st bowel movement
if occurs before birth, fetal distress
if it doesn't occur, anal opening may not be patent
bile gives it a green coloring
163
Formation of liver
hepatic diverticulum (liver bud): ventral outgrowth @W3
cranial portion becomes liver
grows to extend into septum transversum
hepatic cords form & intermingle w/vitelline vv to give the hepatic sinusoids
hepatic cord differentiate into parenchyma & form lining of biliary ducts
connective tissue, haemopoietic tissue, & Kupffer cells derived from mesoderm of septum transversum
later grows to protrude into ventral mesentery→ mesentery modified into falciform ligament & lesser omentum
L+R lobe formation
164
formation of biliary appartus
caudal portion of hepatic divertivulum becomes bile duct
outgrowth from bile duct becomes gallbladder & cystic duct
cystic duct divides bile duct into hepatic duct & common bile duct
bile duct passes drosal to duodenum
165
falciform ligament
attaches liver to body wall
166
BARE area of liver
area of liver that makes contact with diaphragm
NO visceral peritoneum
167
coronary ligament
reflective fold of peritoneum around margins of bare area
168
L+R triangular ligaments
joining of anterior & posterior layers of coronary ligament to these on R+L
169
functions of developing liver
**haematopoiesis**
2nd biggest blood producer after yolk sac
begins W6
accounts for large size drung W7-9
peaks at end of T2 (M6) & declines before birth
**bile production**: begins W12 & stored in intestines
170
development of gallbladder
outgrowth from bile duct
endodermal derivatives: epithelial lining and mucosal glands of gallbaldder & epithelial lining of extrahepatic duct
mesodermal derivatives: lamina propria, muscularis externa, & adventitia of gallbladder
intense miotic activity that fills lumen then recanalized
\*duplication of gallbladder occurs & is asymptomatic
171
biliary atresia
* intrahepatic is very rare (1:100,000)
* extrahepatic 1:10,000
* atresia of hepatic or bile duct
* causes: incomplete recanalization or in utero infection
* symptoms: jaundice
* tx: sx or liver transplant
172
formation of pancreas
from foregut
small ventral & larger dorsal pancreatic buds
both are derivatives of endoderm
ventral bud is rotates dorsally with duodenum to be posterior to dorsal bud
fusion of buds W6
ventral forms uncinate process
dorsal bud becomes head, body & tail
connective tissue & blood vessels from surrounding mesoderm
fuses to dorsal body wall (retroperitoneal)
173
Duct of Wirsung
aka main pancreatic duct
formed from distal portion of dorsal pancreatic duct & ALL of ventral pancreatic duct
enters duodenum at ampulla of vater
174
Duct of Santorini
aka accessory pancreatic duct
formed from proximal portion of dorsal pancreatic duct
may be obliterated during development
175
Ampulla of Vater
aka major duodenal papilla
where main pancreatic & bile ducts enter duodenum
176
histogenesis of pancreas
* exocrine acini
* exocrine cells
* no secretory products during fetal life
* derived from endoderm of pancreatic bud
* Islets of Langerhan
* endocrine
* pale staining area
* unknown origin: endoderm or neural crest
* develop in M3
* alpha cells first: glucagon W15
* beta cells second: insulin M5
* then D cells (somatostatin)
* F cells last
177
ectopic pancreatic tissue
pancreatic tissue found elsewhere in the body
from distal esophagus to primary intestinal loop
most frequently found in duodenum or stomach mucosa
178
annular pancreas
cause: bifid pancreatic bud
encircles duodenum from both sides
partial or total constriction of duodenum
blockages can occur if pancreas becomes inflammed or malignant
179
histology
study of tissue of body & how they are organized to form organs
includes cells & extrcellular matrix
180
types of tissue
1. nervous
2. connective
3. epithelial
4. muscle
most organs are composed of all 4
181
how sample is studied via light microscope
1. fixed
2. embedded
3. sectioned
4. stained
5. observed
182
how sample is studied via electron microscope
1. fixed
2. embedded
3. sectioned
4. coasted with Osmium oxygenate (OsO4)
5. observed under beam of electrons
183
hematoxylin
dyes blue
binds to nucleic acids
thus we see nucleus and acidic regions of cytoplasm (RNA)
also binds cartilage matrix
often used with Eosin
184
Eosin
dyes pink, orange, or red
visualize: collagen fibers, basic regions of cytoplasm, & muscle
often used w/hematoxylin
185
PAS
periodic acid-Schiff
dyes magenta
visualize: glycogen & carbohydrate-rich molecules, i.e. glycocalyx
186
characteristics of epithelia
* flat continuous sheets of cells
* line body surfaces & cavities
* cover every exposed surface
* make up skin & all passageways that communicate w/ outside world: digestive, reproductive, urinary, & repiratory
* avascular: nutrients delivery via diffusion
* anchored by basal lamina
* little to no free intercellular space
* does have nerve supply
* structural/functional polarity
* continuously wear out & replaced via mitosis
* derived from all 3 germ layers
187
functions of epithelia
* protective barrier
* secretion: hormones, enzymes, mucus, etc
* absorption: from lumen
* transport: esp. across
* detection of sensation: ex. taste buds
188
endothelium
epithelium of blood vessels
single layer of mesodermal origin
189
connective tissue
supportive tissue distributed throughout body
very few cells & abundent intercellular substances
190
basal lamina
layer of extracellular matrix secreted by epithelial cells
lies at interface of epithelia & connective tissue
composition vareis between cell types
functions: anchor for overlying epithelium, influence cell polarity and organize proteins in adjacent plasma membrane, & acts as filter
also found surrounding, muscle, adipose, & Schwann cells
**two layers: lamina lucida & lamina densa**
**only seen on electron microscope**
191
reticular lamina
aka lamina reticularis
secreted by underlying connective tissue cells
connected to basal lamina via collagen type VII anchoring fibrils & reticular fibrils
192
basement membrane
fusion of basal lamina & reticular lamina
can be seen w/light microscope
193
lamina lucida
secreted by epithelia
part of basal lamina
contains membrane proteins (integrins) projecting from epithelial membrane w/laminin receptors
194
lamina densa
secreted by epithelia
part of basal lamina
meshwork of collagen type IV coated by perlacan, laminin, & entactin
195
Perlecan
protein w/negatively charged side chains
found in lamina densa of basal lamina
does NOT allow large negative particles to past through basal lamina (important in kidneys)
196
apical domain
face of epitelium toward the lumen
possible modifications: microvili w/associated glycocalyx, cilia, or stereocilia
197
lateral domain
sides of epithelia that connect to each other
198
basal domain
surface of epithelium in contact w/basal lamina
199
microvilli
finger-like projections
function to increase surface area for absorption, secretion, cellular adhesion, and/or mechanotransduction
actin microfilament core anchored by terminal web
#/cell directly correlates to cell's absorptive capacity
1-2microm long & 50-100nm diameter
200
terminal web
network of actin filaments just below plasma membrane
anchors microvilli actin via spectrin
septrin also binds web to cell membrane
201
brush border
distinctive border of vertical striations at apical surface of cell made of microvilli
seen in kidneys & intestines
called striated border in intestines
202
cilia
mictrotubules in 9+2 pattern w/basal bodies & associated motor proteins
beat in rhythmic waves
found in lungs, repiratory tract, & middle ear
lots of mitochondria near basal bodies
203
kartagener syndrome
aka immotile cilia syndrome
inherited
cilia function ineffectively due to **lack of dynein**
males are sterile (non-functional flagella)
mucus collects in airways & sinuses promoting infection
204
stereocilia
actin core, but much larger than microvilli (120microm long & 100-150nm diameter)
passive movement only: vibration in inner ear (mechanoreceptors) & fluid in genital system
in light microscope will recognize either by being told location or presence of sperm
205
squamous cell
wider than they are tall
flat
squame= scale
206
cuboidal cell
height & width are the same
207
columnar cell
cells are taller than they are wide
208
simple cell type
single layer
generally found where absorption & filtration occur
ex. kidney tubule (simple cuboidal)
209
stratified epithelium
more than one layer
found where body linings have to withstand mechanical or chemical insult
layers may be lost w/o exposeing subepithelial layers
ex. skin, vagina, & esophagus
**classified according to most superficial layer**
210
simple squamous epithelium
flat, plate-like w/plump nucleus
locations: blood and lymph vessel lining, certain body cavities, line alveoli of lungs, & parietal layer of Bowman's capsule in kidney
functions: sites for fluid, metabolite, or gas exchange-favored by thinness
211
mesothelium
layer of flat cells of mesodermal origin that lines embryonic body cavity
gives rise to squamous cells of peritoneum, pericardium, & pleura
212
simple cuboidal epithelium
nucleus is spherical & central
location: kidney tubules, covering of ovaries, & ducts of glands
functions: protection, secretions, & absorption
213
simple columnar epithelium
ovoid nucleus
locations: stomach, small intestine, gallbladder and other organs
function: protection, secretion, & adsorption
214
Goblet cells
present among columnar epithelial cells
dialated apical cytoplasm
contains ligh-stained mucus material
215
pseudostratified columnar epithelium
nuclei appear to lie in 2 or more layers, but all cells touch basal lamina
some cells do not touch surface
croweded cells w/various shapes
functions: protection, secretion, & absorption
**only 2 locations: trachea & epididymis**
216
stratified squamous epithelium
thoughest epithelium the body makes
ketatinized: contains keratin, waterproof, most apical layers are dead w/o nucleus or cytoplasm, ex. skin
non-kertinized: esophagus & vagina
217
keratin
tough, fibrous, insoluble protein that forms hair & nails
218
stratified cuboidal epithelium
very rare
in large secretory ducts of sweat & salivary glands
more robust than simple cuboidal
219
stratified columnar epithelium
rare
found in male urethra & in large ducts of some glands
220
transitional epithelium
aka urothelium
lines bladder, ureter, & upper urethra
protect against hypertonic & cytotoxic effects of urine
characterized by superficial layer of dome-like cells that flatten as bladder fills
neitehr squamous nor columnar
221
cutaneous membrane
cover entire body as skin
composed of many layers to protect from: invading pathogens, light, heat, & injury
222
mucous membrane
aka mucosa
lies in cavities that open directly to exterior environment: GI, repiratory, reproductive, & urinary tracts
function: prevent entry of pathogens & microbes
consists of: surface epithelium, supporting CT (lamina propria), basal lamina, & sometimes muscularis (smooth muscle)
secrete mucus to keep membrane moist (not required, but common characteristic)
223
serous membrane
aka serosa
line cavities of body that do NOT open directly to external environment
2 layers: parietal & visceral
secrete lubricating serous fluid to reduce friction w/movement
224
epithelia derived from ectoderm
epidermis & glands on skin
225
epithelia derived from mesoderm
endothelium of blood vessels & serous membranes lining body cavities
226
epithelia derived from endoderm
lining of airways and digestive systems & glands
227
anchoring junctions
zomula adherens
desmosomes/macula adherens
demi-desmosomes
228
occluding junctions
tight-junctions/zonula occludens
229
channel forming junctions
gap junctions
230
tight junctions
aka zonula occludens
separate & maintain apical domain from basolateral domain→ block diffusion of membrane proteins between domains
claudin & occluden proteins form strands to bind adjacent cells together, forming a belt all the way around
function: prevent ion passage between cells, efficiency increases w/# of strands
\*ONLY in epithelial cells\*
231
paracellular pathway
movement of a substance between cells
232
transcellular pathway
movement of substance through cells
233
what modifcaiton is found in basal domain of fluid & ion transporting cells?
lots of mitochondria (for active transport) & infoldings of basal membrane
234
zonula adherens
aka adherens junction
type of anchoring junction
function: joins actin bundle in one cell to another actin bundle in adjeacent cell via cadherin proteins extracellularly
forms adhesion belt around epitelial cells→ reinforces zonula occludens belt
235
desmosome
aka macula adherens
type of anchoring junction
joins intermediate filaments in one cell to those in adjacent cell via cadherin transmembrane proteins
found on lateral domains
functions: resist shearing forces
in epithelia & muscles tissue
major cell-to-cell junction, very strong
NO gap on EM
236
gap junction
aka communicating junctions
function: form channels to allow small, water soluble molecules to pass cell to cell & electrical charge from neuron to neuron→ allow many tissues to act in a coordinated manner
ex. cAMP, cGMP, \<5000MW
occur along LATERAL membranes in epithelia or between cells of any type
formed by abutting pairs of connexons (6 subunit, transmembrane protein)
"no gap" on EM
high [Ca2+] & low pH (sign of necrosis) close conenction to prevent death of one cell from killing those its connected to
237
hemidesmosome
function: anchors intermediate filaments in cell to basal membrane via integrin proteins binding lamini & type IV collage
occur in epithelia to give strong, stable adhesion to basal membrane
238
adhesion plaques
type of anchoring junction
function: joins actin bundle in one cell to extracellular matrix
239
Pemphigus
rare group of blistering autoimmune dz
autoantibodies attack desmosomes→ cells & tissue layers detach doem each other
most common type: pemphigus vulgaris
240
integrin
transmembrane protein found in hemidesmosomes
binds laminin & type IV collagen in basal lamina
241
exocrine gland
secretes product into lumen from apical domain
formed by down growth of epithelium during embryonic development
connecting stalks→ duct
ex. acinar cells secrete pancreatic enzymes
242
endocrine gland
product secrets across basal lamina & picked up by blood vessel in connective tissue
formed by down growth of epithelium during embryonic development
connecting stalks→ lost
ex. insulin from islets of Langerhans in pancreas
243
Goblet cell
only important unicellular gland
mass of secretory vescicles contianing mucinogen at apical region give them their goblet shape
located in epithelia of intestines & conduction portions of respiratory tract
244
mucinogens
large gylcoproteins that swell into mucin with hydration
main component of mucus
245
merocrine glands
cells secrete product by exocytosis
246
apocrine gland
secretes product by budding off portion of plasma membrane
ONLY seen in lactating mammary glands
247
holocrine gland
porduct is screted by entire cell disintegration
ex. sebaceous glands of skin & nose
248
serous gland
secretes proteins, often enzymes
249
mucous gland
secretes mucus
paler than serous on EM
250
functions of connective tissue
structural support
medium for exchange: waste, nutrients, & gases
defense & protection by phagocytic, immune, & mast cells
251
characteristics of loose CT
lots of cell & ground substance w/less fibers (collagen type I, elastin, & reticular fibers [aka collagen type III])
locations: beneath epithelia (as lamina propria), around glandular cells & small blood vessels
initial site of inflammation & allergic reaction
252
characteristics of dense CT
mostly fibers (collagen type I), less cells & ground substance
fibers in bundle arrangmentin various directions→ more strength to withstand stress
locations: dermis of skin & submucosa of intestines
253
ground substance
gel-like to viscous consistency
extracellular fluid found in connective tissue
where diffusion of waste, gases, & nutrients takes place
254
differentiating characteristic of dense regular CT & its locations
tendinocytes: collagen bundles & rows of fibroblasts are oriented in parallel fibers
locations: tendons, aponeuroses, & ligaments
255
epitendineum
connective tissue capsule around tendon
also contains small blood vessels & nerves
256
endotendineum
extension of connective tissue capsule around tendon to subdivide tendon into fascicles
257
elastic ligaments
contain more elastin fibers than collagen fibers
found in spinal column
258
aponeurosis
broad flat tendon
fibers arranged in multiple layers @ 90º angles from adjacent layer
arrangement also seen in cornea
259
fibroblast
connective tissue cell that produces: collagen, reticular, & elastic fibers
260
collagen fibers & their microscopic appearance
every third aa is Gly
characteristic aa= hydroxyproline & hydroxylysine
most abundant type
flexible w/high tensile strength
made of fibrils
light microscope: stain w/eosin, aniline blue, or light green dye
EM: see collagen fibrils that appear as bundle of thread (10-300nm each)
261
fibril
subunit of collagen
made by stackign together of tropocollagen units in overlapping arrangement that creates lacunar regions
lysine & hydroxylysine are cross-linked in adjacent tropocollagens
262
lacunar region
area where tropocollagen fibers do not completely overlap
high # of free radicals→ binds Os→ EM dark bands
263
tropocollagen
280nm long & 1.5nm wide
triple helix of 3 alpha polypeptide chains
string together and make overlapping strains to form fibrils
264
location of collagen type I
loose & dense connective tissue
bone
dentine
265
location of collagen type II
hyaline & elastic cartilage
266
location of collagen type III
aka reticular fibers
267
location of collagen type IV
basal lamina of epithelia
268
procollagen peptidase
membrane bound protein that cleaves nonhelical registration peptides on tropocollagen _extracellularly_
tropocollagen is soluble until this cleavage then becomes insoluble
269
reticular fibers
aka collagen type III
produced by fibroblasts
form fibrils & fibers, but NOT bundles
higher hexose content (6-12% v. 1%)→ stains w/periodic acid Schiff for light microscope
provides support for tissue & organs
locations: around nerves, small blood vessels, and muscle cells & in hemopoientic organs (red bone marros) & in lymphatic tissue (spleen & lymph node, NOT thymus) & in endocrine organs & in liver
270
Ehlers-Danlos syndrome
hyperelasticity of skin & hypermibility of joints
type IV: genetic defect for deficiency of lysyl hydroxylase enzyme→ no hydroxylysine production→abnormal reticular fibers→ ruptures in arteries & large intestines
271
elastic fibers
produced by fibroblasts, chondrocytes, & smooth muscle cells
composed of elastin core & sheath of fibrillin microbibrils
272
elastin
protein rich in Gly & Pro, poor in hydroxyproline, and no hydroxylysine
characteristic aa: desmosine & isodesmosine- both formed from rxn of 4 lysine residues
5x more extensible than rubber
273
fibrillin
organizing center for elastic fibers
forms first & elastin deposited on it
damaged by UV sun exposure→decreased skin elasticity→ wrinkles
274
lamellae
elastin sheet found in the aorta
275
Marfan Syndrome
cause: mutation of fibrillin gene→ lack of resistance in tissues with elastic fibers
changes in skeleton, eyes, & cardiovascular system (mitral valve prolapse & dilation of aorta)
weak periosteum of bones
detached lens & myopia (short-sighted) of eyes
276
functions of nervous system
* sensory input
* integration of data
* control of muscles & glands
* homeostasis
* mental activity
277
homeostasis
process that maintains stability of the body's internal environment in response to changes in external conditions
ex. regulation of temperature & pH
278
neuron
* structural & functional unit of nervous system
* functions:
* accepts, integrates, & sends impulses
* communicates w/other neurons
* excites tissue, ie muscle
* cannot divide/permanently in G0
* parts: soma, dendrites, & axon
279
grey matter
mostly cell bodies of CNS
found on inside of spinal cord & outside of brain
contains microglia in brain
280
whtie matter
white due to myelin of axons
found on the inside of the brain & outside of the spinal cord
281
nerve fiber
axon of a neuron in the PNS
282
nerve
bundle of many nerve fibers & their sheaths
283
ganglion
gathering of neuron cell bodies in PNS
typically site of synapses
284
what are cell bodies called in teh CNS?
nuclei
285
where are sensory neuronal bodies found?
in sensory ganglion
286
where are interneurons found?
CNS
make up 99% of CNS
287
where are motor neuronal bodies found?
CNS
288
what shape do most neurons have?
multipolar
one axon w/two or more dendrites
289
bipolar neuron
one dendrite & one axon
found in sensory neurons of retina, olfactory mucosa, & inner ear only
290
unipolar neuron
aka pseudopolar
no dendrite
single bifurcated process- longer branch goes to periphery & shorter to CNS
found as spinal ganglia (sensory found in spinal nerves) & most cranial ganglia
291
anaxonic neuron
in CNS only
many dendrites & no axon
does NOT produce action potentials
function: regulates elelctrical changes in adjacent neurons
292
glial cells
4 types in CNS & 2 types in PNS
no crossover of types, therefore 6 types total
functions: provide nutrition, support, & protection to neurons
5-10X more abundant in brain that neurons
293
neuropil
intercellular network surrounding cells of CNS composed of cellular processes from neurons & glial cells
294
what organelles extend into neuronal processes?
individulal cisternae of sER
mitochondria
lysosomes
peroxisomes
295
why do nuclei of neuron stain pale?
almost all euchromatin & little to no heterochromatin→ intense synthetic acivity in neurons
296
Nissl bodies
aggregation of RER rubules & polyribosomes
prominent cytoplasmic dark staining structures of neuron cytoplasm w/H&E
appear blue as opposed to lipfuscin granules that will appear brown via light microscope
297
dendrites
thousand/neuron of CNS
receives signal at synapse from other neurons
branch extensively in a near constant diameter
often covered w/dendritic spines- increase surface area for synaptic contact
298
why are dendritic spines important?
they are key for neural plasticity for adaptation, learning & memory
299
when are less dendritic spines found?
increasing age
poor nutrition
300
axolemma
plasma membrane of an axon
301
axoplasm
cytoplasm of axon
302
axon hillock
pyramis region of the soma at the base of an axon
303
initial segment of an axon
unmyelinated
where action potentials begin
just distal to axon hillock
304
node of Ranvier
gaps in myelin sheath along an axon
location where ions can flow in or out of axolemma
305
myelin
lipoprotein material organized into sheath surrounding an axon
function: increase axolemma resistance→ increase speed of action potential propagation down an axon
produced by oligodendrocytes in CNS & Schwann cells in PNS
306
What types of glial cells are found in the CNS?
1. oligodendrocytes
2. astrocytes
3. microglia
4. ependymal cells
307
What type of glial cells are found in PNS?
Schwann cells & satellite cells
308
oligodendrocyte
small round condensed nucleus
few short processes
produces myelin sheths around axons of the CNS
predominant glial cell in white matter
one can myelinate several axons
309
Multiple Sclerosis
1/1,000 in US & europe
autoimmune demyelinating disorder of unknown cause
lesions on myelin sheath of CNS from immune response
symptoms: weakness, tingling, numbness, & blurred vision→ deficit dependent on area of affected CNS
310
bouton
dilation at the terminal end of axonal branch
presynaptic plate
311
what are collaterals and where are they found?
branches of interneurons & some motor neurons that end at synapses influencing many other neurons
312
terminal arborization
branching of an axon at its distal end
313
synapse
junction between two nerve cells or nerve cell & excitable muscle
minute gap across which neurotransmitters pass via diffusion
314
axosomatic synapse
common type of synapse
axon synapses on cell body
315
axodendritic synapse
common type of synapse
axon synapses on dendrite of next neuron
316
axoaxonic
axon synapses on another axon
infrequent type
used to modulate synaptic activity
317
neurofilaments
cell-type specific intermediate filament
abundant in cell body & processes
318
why are microtubules important in axons?
axonal transport in both directions
anterograde: mitochondria, cytoskeletl polymers, vesicles w/neurotransmitters
retrograde: used synaptic vesicles & condition of axon terminals \*\*injury response signaling\*\*
319
dynein
retrograde
+ to -
microtubular motor protein
320
kinesin
anterograde
- to +
microtubular motor protein
321
neurotrophic
relating to growth, differentiation, & survival of neuron
322
How and by what is retrograde axonal transport used against us?
viral infection
ex. herpes simplex, rabies, & polio
\*delay in rabies symptoms correlates to time needed for pathogen to reach somas
323
functions of actin in neurons
* growth, guidance & branching
* morphogenesis of dendrites & dendritic spines
* synapse formation & stability
* axon & dentrite retraction
324
filopodia
slender cytoplasmic projections made ofactin bundles containing +/- receptors
325
lamellipodium
sheet-like foot on leading edge of cell pushed forward by actin polymerization
326
astrocytes
aka astroglia
largest glial cell in size & # in CNS
fucntions: regulate synaptic transmission & neurovascular coupling (form blood-brain barrier)
processes contact thousands of synapses & have end-feet on arterioles & capillaries
also absorb excess neurotransmitters
express glial fibrillary acidic protein
formation of glial limiting membrane
networked together via gap junctions
327
glial fibrilary acidic protein
GFAP
astrocyte cell-type specific intermediate filament protein
used for detecting astrocytomas
328
cerebrum
aka cortex
largest part of brain
associated with higher brain functions
329
cerebellum
10% brain volume/50% total # neurons
controls balance & posture
330
glial limiting membrane
aka glia limitans
innermost meningeal layer at external surface of CNS
made of astrocyte processes
331
microglia
macrophages of CNS
descend from monocytes
evenly distributed thorughout white & grey matter
constantly migrate thru neuropil→ appear amoeboid
function: if damaged cell or microorganism found, proliferate & differentiate into phagocytotic & antigen presenting cells
332
ependymal cells
epithelial-like: line neural tube & ventricles of brain, but NO basal lamina
some have cilia to move CSF around
have elongated basal ends that anchor them to neuropil
333
CSF
cerebrospinal fluid
produced in choroid plexus by modified ependymal cells
fucntions: bath and nourish brain and spinal cord & shock absorption
334
gliosis
nonspecific reactive change of glial cells in response to CNS damage
proliferation or hypertrophy of several types of glial cells
prominent in my dz states: MS & post-stroke
often interferes w/neuronal regeneration
335
astrocytoma
most common type of glioma
vary in growth rate
release excessive glutamate→ damages adjacent neurons via excitotoxic action
336
epineurium
dense irregular fibrous connective tissue that forms external coat of nerves
continues downward to fill space between fascicles
337
perineurium
layers of flattened epithelial cells forming sleeve around fascicle of nerve (bundle of nerve fibers)
cells are joined by tight junctions
function: blood nerve barrier→ blocks passage of most macromolecules protecting nerve fibers & helps maintain their internal environment
338
endoneurium
sparse layer of loose connective tissue that surrounds individual nerve fibers
merges w/Schwann cells
339
Schwann cell
aka neurolemmocyte
producer of myelin in PNS
if unmyelinated, one Schwann cell will protect & separate several small axons
several Schwann cells myelinate one axon→ reason its easier to regenerate myeling in PNS than CNS
340
Schmidt-Lanterman clefs
aka myelin clefts
cytoplasm in spaces between Schwann cell membranes
341
neuromuscular junction
motor neuron branches to form synapse on individual muscle fibers
342
satellite glial cells
principal PNS glial cell
cover surface of neuronal cell bodies in ganglia
function: supply nutrients, protect & cushion soma
343
PNS neural regeneration
peripheral have good capacity for regeneration & return of function
* axon distal to injury degenerates
* 2W later: decrease # of Nissl bodies in soma, nucleus moves peripherally, & macrophages remove debris
* 3W later: Scwann cells proliferate forming tube, multiple axons sprout from proximal unharmed axon, sprouts seek Schwann tube, one axon finds tube & others degenerate
* 3M later: axon lengthens w/in Schwann tube, guided & promoted by factors released by Schwann cells fibroblasts and macrophages, 4mm/day, & re-establishes synaptic contact
reasons unsuccessful: blockage of Schwann cells by scar tissue & if sensory fibers grow to motor end plate
344
glycoaminoglycans
GAGs
long straight chiain poysaccharides of repeating units: N-acetylglucosamine or N-acetylglactosamine & uronic acid sugar
sugars are usually sulfated→ negatively charged→ stain w/basic dyes
attract cations which atract water creates gel-like & resistent to compressive forces
345
proteoglycan
core protein w/GAGs attached
present in all ground substance & surface of some cell types
346
syndecan
transmembrane proteoglycan that links cells to extracellular matrix molecules
347
decorin
proteoglycan w/only one GAG
348
aggrecan
proteoglycan w/more than 200 GAGs
GAGs are chondroitin sulfate & keratin sulfate
349
versican
proteoglycan w/identical GAGs (chondroitin sulfate)
350
proteoglycan aggregates
aggregcan noncovalently bonded to hyaluronic acid via linker proteins
abundant in gound substance of cartilage
351
multiadhesive glycoproteins
function: stabilize extracellular matrix by binding to cell surface, collagen, proteoglycans, & GAGs
ex. fibronectin, laminin, chondronectin, & osteonectin
352
hyaluronidase
enzyme secreted by staphylococcus aureus
chops hyaluronic acid into smaller pieces converting it from gel-like to solid in extracellular matrix
breakdown on ground substance causes rapid spread of microorganism thru CT spaces
353
principal cell
354
myofibroblast
modified fibroblast w/features of smooth muscel cell
abundant in areas of wound healing to contract wound
also seen in periodontal ligament
355
macrophage
356
plasma cell
derived from B-lymphocytes
few in CT, but numerous in inflammatory sites & sites penetrated by bacteria
large ovoid cell w/ extesive rER
nucleus has alternating patches of heter- & euchromatin
function: produce antibodies
357
mast cell
derived from bone marrow
oval to round shape in CT w/small spherical nucleus
metachromatic (changes color w/basic dye) granules due to high levels of heparin (GAG)
function: storage of chemical mediators of inflammatory repsonse
358
allergic response
aka immediate hypersensitivity rxn
1. initial exposure to antigen
2. IgE production by plasma cell & IgE binds receptor on mast cell
3. 2nd exposure, antigen/antibody rxn occurs at mast cell surface
4. discharge of mast cells granules containing primary mediators & secondary mediators (leukotrienes)
359
inflammatory mediators released by mast cells
heparin: anti-coagulant
histamine: dilates and increases permeability in postcapillary venules, increases mucus, & causes bronchiospasm
eosinophil & neutrophil chemotacic factors: attract eosinophils (inactivate histamine & destroy ag/ab complex) & neurtophils (destroy parasite) to inflammatory site
leukotrienes: increase permeability & smooth muscle contraction
prostaglandins: increase mucus secretion
360
mesenchyme cells
multipotent
stellate in shape
pericytes: mesenchyme cell in close association w/small vessels→ can differentiate into smooth muscle or endothelial cell during blood vessel formation or repair
361
adipose
fat cell
arise form embryonic mesechyme cell
brown: multilocular (many fat droplets), dark in color due to # of mitochondria, diminishes during 1st decade of life
white: unilocular, single large fat droplet w/nucleus at periphery
functions of white: energy reserves, insulation, padding of vital organs, & have receptors for insulin, GH norepi & glucocorticords for uptake and release of fatty acids & triglycerides
362
what structure gives rise to the bladder?
urogenital sinus
363
what is meant by the 3 kidney system?
embryologically: pronephros, mesonephros, & metanephros
364
what are the parts of the nephron?
glomerulus, Bowman's capsule, proximal convoluted tubule, loop of Henle, & distal convoluted tubule
365
what are the derivatives of the cloaca?
urogenital sinus & anorectal canal
366
trigone region of the urinary bladder & it's origin
smooth triangular region of internal bladder formed by 2 ureteral orifices & urethral orifice
embryonic origin: mesodermal→ replaced by endodermal epithelium
367
renal agenesis
failure of one or both kidneys to form
cause: failure of ureteric bud to develop or early degeneration or ureters→ bud fails to contact & induce metanephric blastema development
unilateral: other kidney will hypertrophy to conpensate, 1:1000, more often male
bilateral: incompatible w/life, die in first few days, 1:3000, often seen w/oligohydraminos
368
ecoptic kidney
one or more kidney in abnormal position
369
horseshoe kidney
anterior poles of kidneys fuse
usually in lumbar region→ hindered from ascending in the abdomen by the inferior mesenteric artery
370
duplications of ureter
cause: early splitting of ureteric bud
complete: 2 ureters to one kidney
partial: 2 ureters @ kidney that later merge
ectopic ureteral: one normal, second has abnormal openings to vagina, bladder, and/or urethra
371
urachal fistula
persistent allantois
allows urine to leak out of umbilicus
372
urachal cyst
only a small portion allantois persists
NOT connected to umbilicus or bladder
can trap embryonic urine that can be prone to infection
373
urachal sinus
patent allantois in superior portion only
connected to umbilicus
NOT connected to bladder
374
exstrophy of bladder
ventral body wall defect
bladder mucosa opens broadly onto abdominal wall
often seen w/epispadias in males
375
extrophy of cloaca
more severe that exstrophy of bladder
also includes urorectal septum developmental defects & anal canal malformations
376
urogenital ridge
bilateral ridges on either side of descending aorta that give rise to parts of urinary & genital systems
from intermediate mesoderm
377
nephrogenic cord
part of the urogenital ridge that forms the urinary system
378
gonadal ridge
part of urogenital ridge that forms the genital system
379
pronephros
rudimentary & non-functional kidney
most cranial
from intermediate mesoderm
appears early W4 & disappears by the end of W4
7-10 cells clusters in cervical region
pronephric duct runs caudally to cloaca & persist, used by the next set of kidneys
380
mesonephros
large elongated excretory organs
appear late W4 caudal to pronephros
function as interim kidneys for 4 weeks
glomeruli w/mesonephric tubules that open to mesonephric ducts to cloaca (aka Wolffian Duct)
disappear by W8
MALE→ few caudal tubules & duct persist in formation of genital system
FEMALE→ disappear
381
metanephros
permanent kidney
begins formation in W5
function starts in W12
from metanephric diverticulum (ureteric bud) & metanephric mass of intermediate mesoderm (metanephric blastema)
urine passes to amniotic cavity→ swallowed→ recycled in kidney, BUT waste excreted by placenta
382
metanephric mass
aka metanephric blastema
derived form caudal part of nephrogenic cord
383
metanephric diverticulum
aka ureteric bud
outgrowth of mesonephric duct near entrance to cloaca
gives rise to ureter, renal pelvis, major & minor calyces, & 1-3 million collecting tubules
elongates to penetrate metanephric mass
major calyx forms two minor calyces
384
uriniferous tubule
nephron (from metanephric mass) & its collecting tubule (from ureteric bud)
385
positional changes of kidneys during development
start in pelvis
move cranially due to caudal growth of embryo
90º clockwise rotation
finish as retroperitoneal
386
pelvic kidney
when kidney fails to relocate/ascend
387
urorectal septum
mesodermal layer
divides cloaca (endoderm) during W4-W7
into urogenital sinus & anorectal canal
tip forms perineal body
388
urogenital sinus
derived from cloaca
divides into 3 parts:
upper: forms bladder & continuous w/allantois
middle: narrow, male: prostatic & membranous urethra, female: entire urethra
caudal: males: phallic urethra & degenerates in females
389
urachus
thick, fibrous cord
forms from the allantois as its lumen is obliterated
connects umbilicus to apex of bladder
forms median umbilical ligament in adult
390
epispadias
very rare
malformation of the penis- urethra open on upper aspect (dorsum) of the penis
females: urethra develops too far anteriorly.
391
mesonephric ducts
males: become ejaculatory ducts as they move closer together & enter prostatic part of urethra as kidneys ascend
females: degenerate
