Week 2 Flashcards
First week after fertilization
1 layer. cleavage, blastocyst formation and implantation
ampulla
widened part of oviduct where the egg is fertilized
cleavage
Mitotic divisions of embryo without growth
blastomeres
cells of the cleaving embryo. they are totipotent until 4-8 cell stage
totipotent
capable of giving rise to both embryo and fetal contribution to placenta
morula
16 cell embryo
blastocyst (blastula)
the product after cavitation of the morula. cavitation is secretion of fluid to form a cavity
implantation
around day 6-10, the blastula attaches to the uterine wall
pluripotent
cells that can give rise to any type of cell in the body, but not the placenta
embryoblast
inner cell mass of the 6-day embryo that gives rise to the embryo
trophoblast
outer cell mass of 6-day embryo that gives rise to the fetal part of the placenta
week 2 after fertilization
2 layers (bilaminar). embyroblast and trophoblast differentiate into 2 laters each and formation of 2 cavities, amniotic and chorionic
epiblast
columnar cells that secrete fluid to form the amniotic cavity
hypoblast
cuboidal cells that line the blastocyst cavity converting it to the primitive yolk sac
syncytiotrophoblast
a layer of the trophoblast. One cytoplasm with many nuclei. The cells of the syncytiotrophoblast produce hCG
hCG
supports uterine lining and maintains pregnancy
lacunae
spaces in the syncytiotrophoblast. by 12 days they connect to capillaries in the uterine wall to establish placental blood supply
chorionic cavity
formed when spaces within the extraembryonic mesoderm join together.
extraembryonic mesoderm
loose connective tissue formed when hypoblast cells lining the primitive yolk sac proliferate
2 layers of the trophoblast that form during week 2
syncytiotrophoblast and cytotrophoblast
2 layers of the embryoblast that form during week 2
epiblast and hypoblast
yolk sac
blastocycst cavity lined with hypoblast cells
week 3 after fertilization
gastrulation establishes 3 germ layers (trilaminar): ectoderm, mesoderm and endoderm. Epiblast cells give rise to these germ layers while the hypoblast cells form the yolk sac
primitive streak
visible midline structure formed by migrating epiblast cells during the first invagination of the bilaminar embryo. Epiblast cells dive down and replace the hypoblast in this invagination
ectoderm forms
central and peripheral nervous system, epidermis, hair, nails, sensory epithelium of nose, ear, and eye
mesoderm forms
skeletal, smooth and cardiac muscle, cartilage, bone, connective tissue, blood, kidneys, and gonads
endoderm forms
epithelium of gut and its derivatives (liver, gallbladder, pancreas) and epithelium of respiratory system
neural tube
develops from ectoderm overlying the notochord(al process) and forms the nervous system
neural crest
cells on top of the neural tube that migrate away early in development and form the peripheral nervous system
notocord becomes
nucleus pulposis of the intervertebral discs
caudal regression syndrome (caudal dysplasia)
impairs the development of the lower half of the body. Can include lower limbs, lumbar and sacral vertebrae, lower gut, and urinary and genital tracts. Mechanism is abnormal gastrulation resulting in not enough caudal mesoderm. Some possible causes: maternal diabetes, wnt gene defects, vascular anomalies, and teratogens
sirenomelia (mermaid syndrome)
extreme and rare form of caudal dysplasia. Most obvious defect is a fusion of the 2 lower limbs at the midline
sacrococcygeal teratoma
a tumor that develops at the base of the coccyx due to abnormal gastrulation. A germ cell tumor thought to be derived from the primitive streak. Usually Nonmalignant, occur more often in females, and always require surgical removal
agenesis
intrinsic error in morphogenesis. missing organ cause by missing embryonic tissue (renal agenesis)
morphogenesis
process by which embryo takes shape
aplasia
intrinsic error in morphogenesis. missing organ due to growth failure of embryonic tissue (thymic aplasia)
hypoplasia
intrinsic error in morphogenesis. incomplete organ development (microcephaly)
malformation
intrinsic error in morphogenesis. abnormal development of a structure (neural tube defects, cleft lip or palate, congenital heart defects)
disruption
extrinsic error in mophogenesis. normal tissue growth arrested by external force. (amniotic band symdrome)
amniotic band syndrome
a “disruption” of morphogenesis. fibrous bands in amniotic cavity constrict growth of limbs or digits
deformation
extrinsic error in mophogenesis. abnormal growth (but not arrest) resulting in deformed or misshaped structures (potter sequence or symdrome)
potter syndrome
a “deformation” in morphogenesis occurring when fetus is exposed to decreased amniotic fluid so the face and libs are deformed due to lack of cushioing
period of maximal sensitivity
weeks 3 through 8 because organogenesis is occurring. Greatest risk for abnormal development due to exposure to teratogens.
“all or none” period
first 2 weeks after fertilization. Exposure to teratogens during this time will result in spontaneous abortion or have no effect
anomaly
a marked deviation from normal
association
nonrandom appearance of 2 or more anomalies together; cause not known
congenital
present at birth
syndrome
group of anomalies occurring together that has a specific common cause
sequence
primary anomaly itself resulting in additional defects
musculocutaneous nerve
terminal branch of the lateral cord and immediately enters the anterior compartment of the arm and runs between the brachialis and biceps brachii muscles
median nerve
terminal branch of the lateral and medial cords in the axilla and runs distally in association with the brachial artery in the medial aspect of the arm. It crosses anterior to the elbow joint and enters the forearm and continues into the hand through the carpal tunnel
anterior interosseous nerve
a deep branch of the median nerve in the upper parts of the forearm
ulnar nerve
terminal branch of the medial cord that runs distally in association with the brachial artery and median nerve in the medial aspect of the arm. It passes posterior to the medial epicondyle of the humerus and enters the forearm then travels down the medial aspect of the forearm close to the ulna and divides into superficial and deep branch at the wrist
axillary nerve
terminal branch of the posterior cord that exits through the posterior wall of the axilla and passes posterior to the surgical neck of the humerus
radial nerve
terminal branch of the posterior cord that passes out of the axilla into the posterior compartment of the arm in close association to the posterior aspect of the shaft of the humerus. It enters the forearm posterior to the lateral epicondyle of the humerus and travels to the posterior aspect of the hand
Posterior interosseous nerve
a deep branch of the radial nerve in the forearm
Atrophy
loss of a nerve to a muscle will result in atrophy disuse of that muscle
“weakness” of movement
a movement that is accomplished by 2 or more muscles innervated by different nerves will have weakness of movement if only one of the nerves is damaged
“loss” of movement
a movement accomplished by muscles all innervated by the same nerve will have loss of movement if that nerve is damages
loss of muscle function
nearly always results in the opposite function/motion being dominant
most common injury to the axillary nerve
anterior dislocation of the humerus or a fracture of the surgical neck of the humerus
most common injury to the radial nerve
midshaft fracture of humerus
common injury to median nerve
fractures of the elbow and distal humerus or within carpal tunnel (carpal tunnel syndrome)
injury of anterior interosseous nerve (deep branch of median nerve)
may occur with sparing of main median nerve due to compression by nearby muscles or from fractures of the forearm
injury to ulnar nerve
fractures to medial epicondyle or compression of the nerve against the bone or with fractures or lacerations to the ventral medial side of the wrist
injury to musculocutaneous nerve
not common, but can occur
lesions of the brachial plexus
2 most common: upper brachial plexus injury and lower brachial plexus injury that occur at the roots of the plexus
upper brachial plexus injury
ie Erb’s palsy. most often occurs as a birth injury or fall on the shoulder. involves musculocutaneous, axillary, and suprascapular nerves
lower brachial plexus injury
ie Kumpke’s palsy. can occur as a birth injury or sever abduction of the arm. primarily involves the ulnar nerve
5 branches of the axillary artery in the axilla
superior thoracic, thoracoacromial, lateral thoracic, subscapular, anterior humeral circumflex and posterior humeral circumflex
brachial artery
arises in the arm from the axillary artery. has one major branch, the deep brachial, which supplies the posterior compartment
collateral branching of arteries in the upper limb
present around the shoulder, elbow and wrist joints to bypass any blockages of the main artery
most common causes of shoulder pain in adults
subacromial impingement syndrome and rotator cuff problems
steps to physical exam of shoulder
inspection, palpation, ROM, strength testing, special tests
Embryonic genes with roles of body patterning
FGF, Wnt-7a, Shh, and Homeobox (Hox) genes
Proximal to distal formation
ie humerus develops then radius then wrist
Proximal to distal limb development
dependent on FGF (fibroblast growth factor) gene. FGF produced by mesoderm, causing proliferation of ectoderm at the site where the limbs form
AER (apical ectodermal ridge)
ridge formed by the proliferating ectoderm in limb development. AER begins to produce FGF, causing proliferation of the mesoderm
Progress zone
the proliferating mesoderm caused by the FGF produced by the AER
digit formation
apoptosis occurs in the AER to separate it into 5 separate ridges.
Dorsal to ventral limb development
Wnt-7a is the most important gene. It’s a signaling protein expressed by the AER. It activates a gene called LMX-1 in the mesoderm, causing it to form dorsal structures. Without LMX-1, 2 ventral sided would form
Engrailed1
a transcription factor expressed on the ventral side of the limb bud. This represses Wnt-7a
Anterior to posterior limb development
depends on Shh (sonic hedgehog) gene. Shh is signaling protein produced at posterior base of limb buds. Shh diffuses across the limb bud to activate family of transcription factors called homeobox (hox) genes
Zone of polarizing activity (ZPA)
these are the cells that produce Shh
hox genes
define the pattern of differentiation from thumb (anterior or cranial) to little finger (posterior or caudal), as well as segmental organization of entire embryo in a cranial to caudal direction
intermembranous (membranous or dermal) ossification
forms the flat bones of the skull and bones of the face. Mesenchyme cells differentiate directly into osteoblasts
mesenchyme
loosely organized, mainly mesodermal tissue that develops into connective and skeletal tissues, including blood and lymph
osteoblasts
lay down primary or woven bone (irregularly arranged collagen fibers) that is remodeled into lamellar bone (parallel alignment of collagen into sheets)
endochondral ossification
forms the long bones, vertebral column, pelvis, sternum, and skull base. Mesenchyme differentiates into chonroblasts, which produce a cartilage model. Cartilage becomes vascularized, bringing in osteoblasts and restricting chondrocytes to the ends (epiphyses) of the bone
zone of proliferating cartilage
where proliferation occurs at the epiphyseal side of the growth plate in long bones
diaphysis
shaft of long bone
zone of hypertrophic cartilage
chondrocytes toward the diaphysis undergo hypertrophy and apoptosis
zone of ossification
where the chondrocytes mineralize the matrix surrounding the zone of hypertrophic cartilage
bone growth occurs
as long as rate of proliferation=rate of cell death and ossification
dermatome
an area of skin innervated by a single spinal nerve and its dorsal root ganglion
limb defects
rare and mainly hereditary. weeks 4-5 are most susceptible to teratogen induced malformations
meromelia
a reduction defect of the limb resulting in part of the limb being absent
amelia
reduction defect of limb resulting in entire limb being absent
phocomelia
type of meromelia when hands or feet project directly from the shoulder or hip
thalidomide
given to women for nausea in between 1957-62 and caused meromelia when taken during week 5 and amelia when taken during week 4. defined critical period for limb development between 24-36 days
mechanism of thalidomide as teratogen
disruption of the AER and its production of FGF affecting proximal and distal limb development
Polydactyly
formation of extra digits, a duplication defect. Shh is expressed in the anterior limb bud in addition to its usual posterior expression causing mirror duplication of digits . Caused by ZPA duplication and can be inherited or teratogen induced
syndactyly
a dysplasia, or malformation of part of the limb. abnormal fusion of the digits resulting from reduced apoptosis
Spinal cord segments contributing to musculocutaneous nerve
C5, C6, C7
Spinal cord segments contributing to axillary nerve
C5, C6, C7, C8, T1
Spinal cord segments contributing to ulnar nerve
C8, T1
Spinal cord segments contributing to Median nerve
C5, C6, C7, C8, T1
Spinal cord segments contributing to Radial nerve
C5, C6, C7, C8, T1
lateral cord of brachial plexus
gives off musculocutaneous nerve and contributes to median nerve
posterior cord of brachial plexus
gives off axillary nerve and radial nerve
medial cord of brachial plexus
gives off ulnar nerve and contributes to median nerve
Drop arm test
rotator cuff, primarily supraspinatus muscle. Pt abducts arm and slowly lowers it to 90 degrees. Arm will then drop to side if rotator cuff is injured
Impingement tests
Neer’s sign and Hawkin’s test
Speed’s test
Biceps tendon. Forward flex shoulder against resistance while maintaining elbow in extension and forearm in supination. Positive test=tender in bicipital groove
O’brien’s test and Crank test
Labral tear
Instability tests
anterior release and relocation test
Neer’s sign
an impingement test. Patient seated with arm at side and palm down. Examiner stabilizes scapula and raises arm. Positive test=pain. Means rotator cuff tendons are pinched under coracoacromial arch
Hawkin’s test
an impingement test. Patient standing, examiner forward flexes shoulder to 90 degrees and forcible internally rotates arm. Positive test=pain in area of superior glenohumeral joint or AC joint. Suggests subacromial impingement or rotator cuff tendonitis
Obrien’s active compression test
Tests for labral tear (SLAP lesion) patient standing, arm forward flexed 90, adducted 15 to 20 with elbow straight. Full internal rotation so thumb pointing down. Examiner applies downward force. Patient externally rotates arm so thumb pointing up, examiner applies downward force again. Positive test=pain or painful clicking elicited with thumb down and decreased or eliminated with thumb up
Crank test
Tests for labral tear (SLAP lesion). Shoulder elevated to 160 in scapular plane. Gentle axial load is applies through glenohumeral joint with one hand while other does IR and ER. Positive test = pain, catching or clicking in shoulder.
apprehension test - sitting
90 abduction, examiner applies slight anterior pressure to humerus and externally rotates arm. Positive test=patient expresses apprehension that arm will dislocate. May indicate loose capsule and/or ligaments
apprehension test - supine
patient supine with affected shoulder at edge of table and arm abducted 90. Examiner externally rotates by pushing forearm posteriorly. Positive=patient apprehensive
relocation test
performed after positive anterior apprehension test. Patient supine, examiner applies posterior force on proximal humerus while externally rotating arm. Positive=patient expresses relief
Apley scratch test
Reach for upper scapula, compare bilaterally - tests ER and abduction. Reach for lower scapula, compare bilaterally. Tests IR and adduction
Strength of ER
tests infraspinatus and teres minor
Strength of IR
tests subscapularis
Empty can test
arms straight out, elbows locked, thumbs down, arms 30 degrees in scapular plane. Attempt to abduct arms against resistance. Tests supraspinatus
Lift off test
Rest dorsum of hand in lumbar area and try to push examiners hand away. Tests subscapularis
Purpose of connective tissue
provide structural support and connecting framework (or stroma) for all other tissues of body. Main constituent is fibers and ECM
Fibroblast
“resident cell of connective tissue.” produces and maintains ECM
Types of Connective tissue
Loose, Dense regular, and dense irrecular
Loose connective tissue
has more cells than collagen fibers and is generally found surrounding blood vessels, nerves, and muscles
Dense regular connective tissue
more collagen fibers than cells. fibers are preferentially oriented, as in tendons, ligaments, and cornea. Generally poorly vascularized, which impacts healing time
dense irregular connective tissue
more collagen fibers than cells. Fibers are randomly oriented, as in dermis of skin and wall of intestine
main components of ECM
glycosaminoglycans, proteoglycans, adhesive glycoproteins, and collagen
Glycosaminoglycans (GAGs)
long, unbranched polysaccharides consisting of repeating disaccharide units. Highly negatively charged and associate with large amounts of water to create hydrated gels with high viscosity and low compressibility.
Important GAGs in physiology
hyaluronic acid, dermatan sulfate, chondroitin sulfate, heparin, heparan sulfate, and keratan sufate
Proteoglycans
family of macromolecules composed of protein core with at least 1 glycosaminoglycan covalently bonded. Simplest is decorin. Aggrecan is a more complex one, and is found in articular cartilage. Highly negatively charged. Help to organized matrix by interaction with other molecules. Component of basal lamina of epithelial cells
Adhesive glycoproteins
Help facilitate attachment of cells to ECM. Important once are laminin and fibronectin.
Collagen
most abundant proteins in the animal kingdom. The major protein of ECM. At least 28 types. Types I, II, and III are most abundant.
Cartilage
specialized type of connective tissue that consists of chondrocytes embedded in ECM. Usually surrounded by a fibrous connective tissue layer called perichondrium. its avascular; receives nutrition by diffusion through ECM
Interstitial growth of cartilage
division of existing chondrocytes within cartilage
Appositional growth of cartilage
production of new chondroblasts and chondrocytes at at the surface of cartilage from stem cells in perichondrium
Hyaline cartilage
surrounded by perichondrium, chondrocytes surrounded by matrix of type II collagen proteoglycans and water. Found in skeleton of embryo, articular cartilage in joints, and cartilage of respiratory tract
Elastic cartilage
surrounded by perichondrium, chondrocytes surrounded by matrix of type II collagen, proteoglycans, and elastic fibers. Found in external ear and epiglottis
fibrous cartilage
NO perichondrium, chondrocytes surrounded by matrix of type I collage. Resembles dense fibrous CT. Found in intervertebral discs, menisci of knee, and pubic symphysis.
Bone
rigid, inflexible connective tissue in which ECM has been mineralized with calcium and phosphate. It is highly vascularized and metabolically very active. constantly remodeled and reshaped
Organic component of bone ECM
called osteoid; composed of type I collagen and proteoglycans. 3 main noncollagenous glycoproteins are osteocalcin, osteopontin, and osteonectin.
Inorganic component of bone ECM
called bone mineral. consists of calcium and phosphate salt called hydroxyapatite. contributes to strength and rigidity of bone
4 major cell types in bone
osteoblasts, osteocytes, osteoclasts, and osteoprogenitor cells
osteoblast
derived from osteoprogenitor cells. main bone forming cells. generally cuboidal shaped and found on surface of bone. Actively deposit osteoid along the osteoblast-bone interface3. initiate and control the mineralization of the osteoid
primary or woven bone
initially ECM produced by osteoblast. Matrix with loose randomly oriented collagen fibers and low hydroxyapatite
secondary or lamellar bone
remodeled from primary bone. organized sheets of collagen fibers (lamellae) and high hydroxyapatite
osteocyte
osteoblasts that become surrounded in bone matrix stop producing osteoid, flatten out and transform into osteocytes. found in lacunae.
osteoclast
large multinucleated cells found on surfaces of bone whose primary function is to degrade bone matrix
cortical/compact bone
bone matrix arranged into cylindrical structures called osteons. Osteon has central canal called Haversian canal surrounded by 4-10 concentric lamellae of bone cells and matrix.
trabecular/cancellous bone
contains layers of lamellae that form bony trabeculae that project into the marrow cavity. NO osteons. Osteocytes interspersed randomly. surface often covered with osteoblasts and osteoclasts
calcium homeostatsis
done by activity of osteoblasts and osteoclasts. Prevents hypocalcemia and hypercalcemia. Calcium needed for glandular secretion, muscle contraction, and neuronal function.
PTH secretion
activates osteoblast receptors in response to low plasma calcium to secrete osteoclasts
Calcitonin secretion
activates osteoclast calcitonin receptors in response to high plasma calcium to immobilize osteoclasts and retract them from bone surface.
osteoblast
synthesize bone matrix
osteoclast
specialized macrophages derived from monocytes. Secrete acid (H+) and proteases to dissolve bone matrix as osteoid first that later becomes minealized
osteocyte
control local calcium and phosphate levels
bone matrix
consists of type I collagen and hydroxyapatite, which contains 99% of body’s calcium and 85% of its phosphorus
bone turnover
modulated by osteoblasts! osteoclasts are “slaves” to osteoblasts.
RANK/RANK-L, osteoprotegerin (OPG) and M-CSF
RANK
receptor on surface of osteoclasts that, when bound to ligand, stimulates the osteoclast
RANK-L
found on the osteoblasts. it’s the ligand that binds to RANK on the osteoclast to stimulate them
Osteoprotegerin (OPG)
decoy receptor for RANK-L. Made by osteoblasts and prevents RANK-L from binding RANK. Decrease osteoclast activity
M-CSF
secreted by osteoblasts to stimulate osteoclasts
