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Anat/phys spch swal

Embryonic Development Study Guide

The primordial areas that give rise to the mucous membrane of the tongue first appear during the seventh or eighth week
tuberculum impar a small elevation that is located between the lateral lingual swellings
lateral lingua swellings Embryos in their fifth week often show evidence of paired thickenings called this on the internal surface of the mandibular arch; they consist of rapidly proliferating mesoderm (mesenchyme) covered by epithelium
mesenchyme rapidly proliferating mesoderm covered by epithelium
L. tuberculum a nodule or small eminence
L. copula or the hypobranchial eminence a second midline swelling; a joining together
hypobranchial eminence It bridges the second and third branchial arches at the midline, and a transverse groove separates is a caudal part that forms the epiglottis; ventrally it approaches the tongue rudiment, spreading ventrally in the form of a "V,"
hypobranchial eminence (continued) and forming the posterior or pharyngeal part of the tongue
Epigottis the caudal part where the transverse groove separates that forms this
sulcus terminalis in the adult, the union of the anterior and posterior parts of the tongue is marked by this
foramen caecum the apex of the sulcus terminalis
Tissue on either side of the copula proliferates rapidly until, by the end of the seventh week, a distinct tongue-like structure is evident
anterior lingual primordia the cephalic pair, which is located at the level of the first branchial arch
root primordia the caudal pair is located at the level of the second branchial arch
occipital somites where the musculature of the tongue comes from; there are three of these
mitosis the process of a sexual reproduction in which the parent simply divides into equal parts, usually exact duplicates; it is a mechanism that maintains a constant chromosome all offspring have the same number of chromosomes as the parent cell
chromosome a packaged and organized chromatin, a complex of macromolecules found in cells, consisting of DNA, protein and RNA; the main information-carrying macromolecule is a single piece of coiled double-stranded DNA, containing many genes,
chromosome (continued) regulatory elements and other non-coding DNA
five phases of cell division interphase (resting phase), prophase, metaphase, anaphase, and telophase
interphase this term refers to a cell at resting phase, so it may imply that no activity is taking place in the nucleus of the cell, but this is hardly the case; during this phase nuclear growth is occurring at an accelerated rate
prophase toward the end of the interphase the chromosomes, which are not normally visible, begin to take on a granulated appearance; the first sign that cell division is imminent is when the chromosomes become visible as long thin threads (chromatids)
prophase (continued) throughout this phase, the chromatids become increasingly visible, largely due to the fact that they become shorter and thicker; in addition, the nucleoli, which are formed by chromosomes diminishing in size and finally disappear
The first sign of cell division it is imminent when the chromosomes become visible as long, thin threads (chromatids)
chromatids thin threads; one copy of a duplicated chromosome, which is generally joined to the other copy by a single centromere
nucleoli/nucleolus a small, typically round granular body composed of protein and RNA in the nucleus of a cell; it is usually associated with a specific chromosomal site and involved in ribosomal RNA synthesis and the formation of ribosomes
metaphase begins with the disappearance of the nuclear membrane; at the same time a new structure appears in the cytoplasm; it is a long, thin chain of protein molecules (the spindle) that is oriented between the two "poles" within the cell body;
metaphase (continued) when the spindle is well developed, the chromosomes move randomly through the cytoplasm at first and finally settle in a region midway between the poles of the spindle
spindle a long thin chain of protein molecules that is oriented between the two "poles" within the cell body
nuclear membrane also known as the nuclear envelope; the double lipid bilayer membrane, which surrounds the genetic material and nucleolus in eukaryotic cells
anaphase in this phase, the paired chromosomes are seemingly pulled from the mid-region toward opposite poles (presumably by the fine fibrils of the spindle)
anaphase (continued) this migration continues until, at the very end of it, the chromosomes form a densely packed group at each of the two poles
telophase in this phase, the events that occurred back in prophase are "replayed," but in reverse order; thus a nuclear membrane forms around the chromosomes, which uncoil to form slender threads again, and the nucleoli make their appearance
telophase (continued) a cell wall forms in the region of the spindle, which slowly disintegrates leaving two cells, separated from one another and ready to undergo a growth period before the next division is intiated
gametes sexual germ cells either egg (female) or sperm (male)
What are gametes and what role do they play in gametogenesis? sexual reproduction, which is well established in both simple and complex forms of life, involves the union of two sexual germ cells (gametes)
What are gametes and what role do they play in gametogenesis? (continued) two gametes (one male and one female) unite to form a single new cell (zygote) that gives rise to a new individual organism
zygote two gametes (one male and one female) unite to form this single new cell that gives rise to a new individual organism
What is the length of the embryo at 3 weeks of age? it is about three mm in length
mandibular arch the first of the branchial arches; it ultimately gives rise to the lower lip, the muscles of mastication (masseter muscle), the mandible proper, the anterior portion of the tongue, and some of the structures of the middle ear
lower body of the hyoid bone the third arch gives rise to this
pharyngeal constrictors the caudal portions of the branchial arches (caudal arches) give rise to the palatine muscles and to this, but the precise contributions are unknown and a source of much disagreement
caudal arches the caudal portions of the branchial arches; give rise to the palatine muscles and pharyngeal constrictor muscles
appearance of stomodeum or primitive mouth 2nd week
Formation of the mandibular arch on either side; maxillary processes bud out from the mandibular arch; nasal placodes appear 3rd week
rupture and disappearance of buccopharyngeal membrane 4th week
appearance of frontonasal process; olfactory pits widely separated; appearance of globular processes 5th week
union of lateral nasal with maxillary processes; partial division of stomodeum into an upper and lower cavity 6th week
union of the three portions of the palate commences anteriorly; completion commences anteriorly; completion of the upper lip by fusion of globular processes 8th week
completion of union of palatine segments, the uvula being the last to be completed 10th week
cleft palate forms complete, incomplete, unilateral, or bilateral
cleft lip and palate the most common facial deformities as a result of embryonic development; variations of a type of clefting (a fissure or opening - a gap) congenital deformity caused by abnormal facial development during gestation
congenital disease/disorder a condition existing at birth and often before birth, or that develops during the first month of life (neonatal disease)
gestation the carrying of an embryo or fetus inside a mother
cleft lip and palate's occurence one of about a thousand births (1/1000)
cleft lip and palate principle cause facial development is sometimes interrupted during the period when the fusion between the primitive palate and the palatine processes of the maxillae is normally taking place; facial deformities of various degrees of severity may occur
other causes of cleft lip and palate they are not known with certainty; factors such as intrauterine anoxia, toxic poisoning, high concentrations of cortisone, an inherent lack of mesoderm, and heredity seem to be implicated
ratio of cleft lip and palate males are far more subject to the deformity than are females; 2 to 1
more on ratio of cleft lip and palate males are less subject to minor palatal defects than are females, but considerably more subject to severe types of defects
cleft/clefting a fissure or opening - a gap
The cricoid cartilage is the derivative of the fifth arch
ovulum/egg the female germ cell
sperm the male germ cell
meiosis the process by which the reduction of the number of chromosomes in the sexual germ cell is accomplished by an extraordinary type of cell division,
meiosis (continued) which consists of two nuclear divisions during the maturation of the sex cell, with only one division of chromosomes
spermatogenesis consists the final phase for sperms
oogenesis consists the final phase for eggs
diploid number (2N) the number found in all body cell
haploid number (N) one-half the diploid number found in the sex cells
Y chromosome determines the sex of the embryo
chemical barrier when the membrane repairs quickly, it sets this up, which prevents additional sperm from entering
mitotic division the cell division that follows the fertilization of an egg or zygote, and as a result each daughter cell possesses 46 chromosomes
blastomeres of the two cells that takes place within 24 hours of fertilization
morula a round mass of cells that has been recovered from the uterine cavity on or about the third day after fertilization
blastocyst a fluid-filled sphere formed by the growth of morula
blastocoele the fluid-filled cavity of the blastocyst
trophoblasts an outer layer of cuboidal cells, which surrounds an inner cell mass
animal or embryonic pole inner cell mass where they continue the decidua of the uterus and become more complex
placenta the fetal membranes, which establishes communication between the mother and embryo by means of umbilical cord
umbilical cord the fetal membrane, which establishes communication between the mother an embryo
primary yolk sac the endodermal cells proliferate at the periphery of the inner cell mass and ultimately and completely line the inside of the trophoblast to form it
secondary yolk sac the other part created by folding that persists for some time
extraembryonic mesoderm about the time the yolk sac is being formed, cells from the inner surface of the trophoblast proliferate to form a loose network of this
magma reticulare the developing mesoderm fills the blastocoele and pushes the primary yolk sac away from the trophoblast whereupon the sac shrivels and atrophies
amnionic cavity a fluid-filled cavity
amnionic membrane or amnion covers the amnionic cavity
embryonic disc the inner cell mass and consists of columnar ectodermal cell in the floor of the amnionic cavity and a subjacent layer of cuboidal endodermal cells which forms the roof of the yolk sac
enzymes produced by the cells of the trophoblast, erode the deciduous of the uterine lining and facilitate interstitial implantation of the blastocyst
syncytiotrophoblast one type of cell that proliferates so rapidly that the individual cells do not form cell boundaries
cytotrophoblast one type of cell that does produce cell boundaries
trophoblastic villi fingerlike processes that begin to extend out in all directions from the blastocyst
chorionic villi when somatopleuric extraembryonic mesoderm invades them
chorionfrondosum the restricted area where villi continue to develop
intraembryonic mesoderm the significance of the primitive streak that forms this
Hensen's node a small area of proliferating cells that produces a node from which a strip of cells grows cephalically along the midline axis of the embryo between the ectoderm and endoderm
notocord the midline strip of cells sandwiched between the ectoderm and endoderm; the primitive axial skeleton of the embryo
prochordal plate the small area of tightly bound ectoderm and endoderm
buccopharyngeal membrane the prochordal plate forms this
medullary or neural plate the thickening of the ectoderm in the area immediately overlying the notocord, the lateral margins of which grow upward to form the paraxial neural folds
neural folds the lateral margins of which grow upward
neural groove between the neural folds
neural tube the folds that meet at midline, fuse and form this, from which all the future central nervous system is developed
sclerotome the medialmost region of a somite
phrenic nerve the nerve that supplies the diaphragm with motor fibers; this nerve emerges from the fourth and fifth cervical nerves of the embryo
latissimus dorsi it is from cervical myotomes and ultimately migrates to the lower thoracic and lumbar vertebrae, and to the iliac crest
aponeurotic sheets can be attributed to muscle degeneration; examples are the abdominal aponeurosis and the gala aponeurotica which connects the occipitalis and frontalis muscles
dermis or chorium the most lateral portion forms the deformatone which develops into this
cephalic fold very rapid growth of the cephalic end of the embryo causes this in which the prochordial plate (now known as the buccopharyngeal membrane) is folded under the embryonic head
intraembryonic coelom the lateral plate mesoderm divides into two layers thus producing this cavity it subsequently becomes divided into the pericardial, pleural, and peritoneal cavities
somatopleuric intraembryonic mesoderm the upper layer of the lateral plate mesoderm that is in contact with the ectoderm of the dorsum of the embryo
splanchnopleuric intraembryonic mesoderm the lower layer of the lateral plate mesoderm that is in contact with endoderm
ectoderm the outermost layer, and it forms the epidermis of the skin, the entire nervous system, hair, nails, and epithelial tissue
mesoderm the intermediate layer, and it ultimately gives rise to most of the connective tissue in the body; that is forms the bones, muscles, blood vessels, and cartilages of the body
endoderm the deepest of the three layers, gives rise to the epithelial lining of the entire digestive tract (except for the linings of the mouth an pharynx, which are formed by ectoderm) and the epithelial lining of the entire respiratory tract
endoderm (continued) because it lines the body cavity, it is sometimes called the "inner skin"
prosencephalon during the flexion stage, this smooth, relatively undifferentiated bulge, which is the forebrain or anterior brain vesicle of the embryo is called this; it is covered by a thin layer of ectoderm and mesoderm
primitive mouth stomodeum means this, and it might be regarded as the topographical center of the developing facial structures
branchial region the lateral walls of the anterior part of the foregut in this become differentiated into a series of transversely placed elevations with depressions between them
branchial grooves/gill clefts the depressions in the branchial region are known as this; they are not true clefts, however, because the space is filled with ectoderm and endoderm
branchial arch as the paired (right and left) elevations between adjacent branchial grooves grow, they meet at the midline in such a manner that each forms this
hyoid arch the second branchial arch that gives rise to such structures as the upper body and lesser horns of the hyoid bone, the stapes, and the muscles of facial expression
arches 3 to 6 the remaining branchial arches are designated only by number and have no names assigned to them
The fourth and fifth branchial arches give rise to the arytenoid and cricoid cartilages of the larynx and cartilages of the trachea
the first branchial groove eventually develops into the concha of the auricle and into the external auditory meatus
The ventral aspect of the forebrain is crucial to the development of the face; although it is relatively undifferentiated during the third week, it eventually develops into the frontonasal process
During this same pariod, the first branchial or mandibular arch appears as a single transverse bar located immediately caudal to the oral groove; some limited proliferation may have taken place, giving rise to as yet undifferentiated maxillary process, on either side
nasal or olfactory placodes sometime during the latter part of the third or beginning of the fourth week, two areas,on either side of the frontal process, begin to proliferate to form thickenings called these
nasal pits during the fourth week, rapid growth in the areas immediately surrounding the olfactory placodes results in the formation of these two
The nasal pits now divide the previously undifferentiated frontonasal process into a medial and two lateral nasal processes, on on either side
globular processes these are known as the two lateral angles that become more and more prominent as proliferation of the medial nasal process continues
oronasal grooves the maxillary processes are separated from the medial nasal processes by these
nasoptic grooves the maxillary processes are separated from the lateral nasal processes by these
The ___________ and ______________ are of special interest because if they fail to be obliterated the face will be malformed oronasal and nasoptic grooves
cervical sinus the third and fourth arches are obliterated to form this; a temporary structure located between the hyoid arch in front an thoracic wall behind; due to the fusion of its walls, the sinus eventually disappears
primary palate the shelf of tissue that separates a portion or the oral and nasal cavities when fusion is completed between the maxillary and medial nasal processes (globular processes) after the latter part of the sixth week
Fusion between the maxillary and medial nasal processes (globular processes) begins during the latter part of the sixth week
nasal laminae the tissue in the area of the globular processes is projected posteriorly into the nasal cavity to form two plates called this at the same time as the maxillary and medial nasal processes fuse
nasal septum during subsequent development, as the nasal pits come closer together, these nasal laminae ultimately fuse to form this
philtrum a facial landmark known as this indicates the point of fusion between the maxillary and globular processes
choanae the olfactory pits that are formed because of the growth of the nasal processes; also known as concha
bucconasal membrane these choanae, each being closed off by a thin epithelial wall is called this
median sulcus a pronounced constriction known as this divides the mandibular arch into halves around the beginning of the sixth week
lateral sulci on either side, small furrows called this develop; these disappear at the same time the nasal and maxillary processes fuse in the upper facial region
palatine process of the maxillae the medially directed portion and horizontal process of the maxilla; it forms the anterior three quarters of the hard palate
tongue in the earlier stages of the formation of the secondary palate, this is extended in height so that it almost completely fills the oral cavity and in fact, touches the tissue that will eventually develop into the nasal septum
tegmen oris the roof of the mouth that is bounded laterally and anteriorly by the tectal ridge
tectal ridge an inward projection of the globular process
foregut caudal to the primitive mouth, this becomes widened and flattend dorsoventrally to form the pharynx
pharyngeal pouches four pocket-like diverticula arise from it laterally; each of them are located opposite an external branchial groove
thyroid primordium arising medially in the floor of the pharynx at the level of the first and second arches is a band of endoderm called this
laryngeotracheal groove this a median structure on the floor of the pharynx; the rudiments of the respiratory system appear in the fourth week
laryngeotracheal tube the groove deepens, and its lips fuse to form this; it is lined with endoderm, and from this, the epithelial lining of the entire respiratory tract is developed; the cranial end of this develops into the larynx, while the remainder forms the trachea
main bronchi/right & left lung buds at the caudal extreme of the tube, two lateral outgrowths arise to form these
Failure of this epithelium to resorb explains the presence of congential _______________ and various types of ___________ laryngeal webs; papillae
lung tissue differentiation (phases) three phases are recognized: glandular, canalicular, and alveolar
glandular phase in this phase, the bronchial divisions are differentiated but the epithelial tissue resembles glandular tissue
canalicular phase in this phase, the respiratory segments and other parts are delineated and establish a relationship with the expanding vascular system; the lungs are not functional at this stage, which may extend into the sixth month
alveolar phase this phase extends from six months, but new bronchi and alveoli continue to be formed after birth; during their development, the lungs migrate in a caudal direction,
alveolar phase (continued) and at birth, the bifurcation of the trachea is located at the level of the fourth thoracic vertebra
palatopterygoquadrate bar the dorsal cartilage of the mandibular (first branchial) arch
Meckle's cartilage the ventral cartilaginous element of the mandibular arch extends from the developing otic capsule into the mandibule and meets its fellow from the opposite side; its dorsal end forms the maslleus and the incus,
Meckle's cartilage (continued) and although the cartilage itself disappears, its sheath remains as the anterior malleolar and the sphenomandibular ligaments
Reichert's cartilage the cartilage of the hyoid (second branchial) arch; it also extends from the otic capsule to the midline ventrally; the dorsal end separates and becomes enclosed in the developing tympanic cavity as the stapes
Reichert's cartilage (continued) it also gives rise to the styloid process of the temporal bone, the stylohyoid ligament, and the lesser horns and upper body of the hyoid bone; the vental portion of arch 3 gives rise to the greater horns and lower body of the hyoid bone
auricle this develops around the first branchial groove and is derived from tissue of the mandibular and hyoid arches
hillocks at about six weeks these six small elevations appear-three on the caudal border of the first arch and three on the second arch
auricular fold an elongated elevation
external auditory meatus ear canal; represents the first branchial goove; the ectodermal floor of the groove is in contact with the endoderm of the first pharyngeal pouch
four periods of development for teeth growth, calcification, eruption, and attrition
growth the beginning formulation of a tooth bud, specialization and arrangement of cells to outline the future tooth, and deposition of the enamel and dentin matrix
calcification the hardening of the enamel and dentin matrix by deposition of inorganic salts, largely calcium
eruption the migration of the rather fully developed tooth into the oral cavity
attrition the wearing away of the enamel on the contact and occlusal surfaces of the erupted tooth
tooth bud the initial stage of tooth growth is the formation of this from the epithelial tissue contained in what will eventually become the jaws and associated connective tissue
oral epithelium during the fifth or sixth week, this is separated from the subjacent connective tissue (mesoderm) by a thin basement membrane
dental lamina the growing epithelium extends into the mesoderm (from which bone and other connective tissues will develop) to form a thin strand of tissue called this
dental papilla as proliferation continues the dental cap begins to surround and engulf mesoderm; this mesoderm, which eventually be located inside the tooth, is known as this
dental papilla (continued) at this stage, the dental cap is surrounded by mesoderm (which ultimately forms the cementum of the tooth and peridontal tissue) and it also surrounds mesoderm (which gives rise to the dental pulp and contributes to the formation of dentin)
enamel cells (ameloblasts) those in contact with the papillae undergo modifications and acquire the ability to form enamel; they are identified as this
external enamel epithelium the cells in the outer layer of the cap are called this
enamel pulp these cells, plus the cells in the intermediate layer, become modified to form this
enamel organ when these changes have been completed, the special fental germ (dental cap) is spoken of as this; at this stage of development, this has assumed a bell shape
dental sac the cells that become extremely dense and give rise to a fibrous layer of tissue known as this
ameloblasts when these cells have become fully developed, they are known as this, and they form the enamel matrix, which is structurally the same as the mature enamel in the erupted tooth, but has a consistency of cartilage
odontoblasts the cells in contact with the inner layer of special dental germ become modified to form this; these cells are responsible for the formulation of the dentin of the crown of the tooth
pulp the very center of the papilla does not undergo differentiation, but remains as this of the tooth
root this of the tooth, which is an outgrowth of the dental germ, begins to be formed just before clinical eruption occurs; growth of this, however, continues for some time after eruption
Created by: ryanriggs_90



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