Podcast
Questions and Answers
What type of muscle tissues are striated (skeletal) muscles, smooth muscles, and cardiac muscles?
What type of muscle tissues are striated (skeletal) muscles, smooth muscles, and cardiac muscles?
- Voluntary, involuntary, and cardiac
- Striated, smooth, and cardiac (correct)
- Skeletal, cardiac, and involuntary
- Cardiac, smooth, and skeletal
From which type of mesoderm do the skeletal muscles of the trunk derive?
From which type of mesoderm do the skeletal muscles of the trunk derive?
- Branchial mesenchyme
- Somites
- Cranial paraxial mesoderm
- Paraxial mesoderm (correct)
Where do most of the craniofacial muscles originate from?
Where do most of the craniofacial muscles originate from?
- Somites
- Cranial paraxial mesoderm
- Branchial mesenchyme (correct)
- Myotomes
What is the process by which mesenchymal cells of the myotomes differentiate into muscular progenitors called myoblasts?
What is the process by which mesenchymal cells of the myotomes differentiate into muscular progenitors called myoblasts?
What type of bone formation involves the formation of bones directly from mesenchyme?
What type of bone formation involves the formation of bones directly from mesenchyme?
Which process involves differentiation of mesenchyme into chondroblasts and the formation of a cartilaginous model?
Which process involves differentiation of mesenchyme into chondroblasts and the formation of a cartilaginous model?
Primary and secondary ossification occurs in which types of bones?
Primary and secondary ossification occurs in which types of bones?
What remains in the joints as articular cartilage and growth plates?
What remains in the joints as articular cartilage and growth plates?
Where are growth plates located in relation to the diaphysis and epiphysis?
Where are growth plates located in relation to the diaphysis and epiphysis?
What is the fibrous layer surrounding bones called?
What is the fibrous layer surrounding bones called?
Where does endochondral ossification take place in long bones?
Where does endochondral ossification take place in long bones?
What type of bone formation forms flat bones directly from mesenchyme?
What type of bone formation forms flat bones directly from mesenchyme?
Which of the following involves formation of a cartilage model which is gradually replaced by bone?
Which of the following involves formation of a cartilage model which is gradually replaced by bone?
The differentiation of mesenchyme into chondroblasts and formation of a cartilaginous matrix is part of which process?
The differentiation of mesenchyme into chondroblasts and formation of a cartilaginous matrix is part of which process?
What allows the bone to grow in length?
What allows the bone to grow in length?
Where does primary and secondary ossification occur?
Where does primary and secondary ossification occur?
During muscle development, what creates myosin and actin resulting in the striated muscle appearance?
During muscle development, what creates myosin and actin resulting in the striated muscle appearance?
What is the population of quiescent myoblasts that remain near muscle fibers, ready to differentiate and form new muscle fibers when needed?
What is the population of quiescent myoblasts that remain near muscle fibers, ready to differentiate and form new muscle fibers when needed?
From which part of the body do the dorsal (epaxial) muscles derive during myogenesis?
From which part of the body do the dorsal (epaxial) muscles derive during myogenesis?
Which type of muscle forms from the visceral splanchnic mesoderm surrounding the heart tube?
Which type of muscle forms from the visceral splanchnic mesoderm surrounding the heart tube?
What process can result in intramembranous ossification and endochondral ossification during muscle development?
What process can result in intramembranous ossification and endochondral ossification during muscle development?
What type of muscle is associated with thoracic and abdominal viscera?
What type of muscle is associated with thoracic and abdominal viscera?
What is the origin of the ventral (hypaxial) muscles during myogenesis?
What is the origin of the ventral (hypaxial) muscles during myogenesis?
Which cells form new muscle fibers when needed?
Which cells form new muscle fibers when needed?
What is the process of bone development involving mesenchyme from different sources?
What is the process of bone development involving mesenchyme from different sources?
What is the specific origin of the cardiac muscle cells called cardiomyocytes?
What is the specific origin of the cardiac muscle cells called cardiomyocytes?
From which mesoderm does smooth muscle associated with thoracic and abdominal viscera derive?
From which mesoderm does smooth muscle associated with thoracic and abdominal viscera derive?
Which structure induces the mesoderm to continue growing into a limb?
Which structure induces the mesoderm to continue growing into a limb?
What differentiates into specific bones and muscles in the developing limb?
What differentiates into specific bones and muscles in the developing limb?
What is responsible for causing the interdigital zones to degenerate in the developing limbs?
What is responsible for causing the interdigital zones to degenerate in the developing limbs?
In which pattern does the developing limbs undergo regional differentiation?
In which pattern does the developing limbs undergo regional differentiation?
What are the three stances based on how mammals' limbs touch the ground?
What are the three stances based on how mammals' limbs touch the ground?
Which type of animals stand or walk on their digits and retain the original embryonic pattern of five digital fingers?
Which type of animals stand or walk on their digits and retain the original embryonic pattern of five digital fingers?
What is a congenital defect characterized by the presence of extra digits?
What is a congenital defect characterized by the presence of extra digits?
'Achondroplasia' is a form of dwarfism caused by what?
'Achondroplasia' is a form of dwarfism caused by what?
'Arthrogryposis' is a condition resulting in what?
'Arthrogryposis' is a condition resulting in what?
'Brachydactyly' is characterized by what?
'Brachydactyly' is characterized by what?
What are the two types of ungulates mentioned in the text?
What are the two types of ungulates mentioned in the text?
What is responsible for creating morphogenic gradients for each zone of the developing limb?
What is responsible for creating morphogenic gradients for each zone of the developing limb?
How does bone growth in length occur?
How does bone growth in length occur?
What is responsible for the growth in diameter of bones?
What is responsible for the growth in diameter of bones?
Which process is responsible for joint development?
Which process is responsible for joint development?
What is required for proper synovial joint development?
What is required for proper synovial joint development?
How do vertebrae initially develop?
How do vertebrae initially develop?
What is the origin of the intervertebral disc regions?
What is the origin of the intervertebral disc regions?
How do ribs develop?
How do ribs develop?
What is responsible for the formation of sternebrae?
What is responsible for the formation of sternebrae?
What initiates limb development?
What initiates limb development?
What encloses the neural tube during vertebrae development?
What encloses the neural tube during vertebrae development?
What differentiates into fibrous, cartilaginous, or synovial joints?
What differentiates into fibrous, cartilaginous, or synovial joints?
What is needed for proper synovial joint development to prevent ankylosis?
What is needed for proper synovial joint development to prevent ankylosis?
What are the two components that assemble the bones of the head or skull?
What are the two components that assemble the bones of the head or skull?
From which part of the body does the visceral skeleton of the face differentiate?
From which part of the body does the visceral skeleton of the face differentiate?
How do the individual bones of the face develop?
How do the individual bones of the face develop?
From which pharyngeal arch does the nerve supply sensation to the anterior 2/3 of the tongue?
From which pharyngeal arch does the nerve supply sensation to the anterior 2/3 of the tongue?
Which ectodermal structure gives rise to the individual teeth in the process of tooth development?
Which ectodermal structure gives rise to the individual teeth in the process of tooth development?
Which type of mesoderm does the cardiac muscle cells called cardiomyocytes originate from?
Which type of mesoderm does the cardiac muscle cells called cardiomyocytes originate from?
Where does the invagination of surface epithelial cells occur during the typical formation of exocrine glands like salivary glands?
Where does the invagination of surface epithelial cells occur during the typical formation of exocrine glands like salivary glands?
Which embryonic structure forms the nose, nasal cavity, and primary palate?
Which embryonic structure forms the nose, nasal cavity, and primary palate?
What congenital abnormality involves the failure of the palate to close along the midline?
What congenital abnormality involves the failure of the palate to close along the midline?
From which branchial arch does the rostral two-thirds of the tongue originate?
From which branchial arch does the rostral two-thirds of the tongue originate?
Which of the following embryonic structures contributes significantly to the development of the head in mammals?
Which of the following embryonic structures contributes significantly to the development of the head in mammals?
What is the origin of the flat bones that ossify to form the roof of the cranium in mammalian embryos?
What is the origin of the flat bones that ossify to form the roof of the cranium in mammalian embryos?
What is the function of the splanchnocranium in mammalian embryos?
What is the function of the splanchnocranium in mammalian embryos?
From which embryonic structure does the visceral skeleton of the face differentiate in mammalian embryos?
From which embryonic structure does the visceral skeleton of the face differentiate in mammalian embryos?
Which nerve supplies sensation to the anterior 2/3 of the tongue?
Which nerve supplies sensation to the anterior 2/3 of the tongue?
From which pharyngeal arch do the muscles of the tongue originate?
From which pharyngeal arch do the muscles of the tongue originate?
What gives rise to the individual teeth during tooth development?
What gives rise to the individual teeth during tooth development?
Where does the invagination of surface epithelial cells occur during the typical formation of exocrine glands like salivary glands?
Where does the invagination of surface epithelial cells occur during the typical formation of exocrine glands like salivary glands?
What is responsible for forming the outer layer of the tooth or the crown during tooth development?
What is responsible for forming the outer layer of the tooth or the crown during tooth development?
Where do the parotid, zygomatic, and labial and buccal accessory salivary glands derive from?
Where do the parotid, zygomatic, and labial and buccal accessory salivary glands derive from?
What differentiates into odontoblasts during tooth development?
What differentiates into odontoblasts during tooth development?
In which type of gland development do surface epithelial cells undergo localised proliferation?
In which type of gland development do surface epithelial cells undergo localised proliferation?
Which nerve innervates the muscles of the tongue?
Which nerve innervates the muscles of the tongue?
From which pharyngeal arch does the posterior 1/3 of the tongue (root) derive?
From which pharyngeal arch does the posterior 1/3 of the tongue (root) derive?
What process results in the formation of sternebrae?
What process results in the formation of sternebrae?
Which part of the skull forms the facial skeleton?
Which part of the skull forms the facial skeleton?
What structure forms as a result of the separation of the oral and nasal cavities?
What structure forms as a result of the separation of the oral and nasal cavities?
What congenital abnormality involves the failure of the palate to close along the midline?
What congenital abnormality involves the failure of the palate to close along the midline?
From which branchial arch does the rostral two-thirds of the tongue originate?
From which branchial arch does the rostral two-thirds of the tongue originate?
Which type of congenital abnormality involves a failure of the palate to close along the midline, affecting various parts of the palate?
Which type of congenital abnormality involves a failure of the palate to close along the midline, affecting various parts of the palate?
What does the nasal cavity develop from?
What does the nasal cavity develop from?
What separates the oral and nasal cavities?
What separates the oral and nasal cavities?
What are congenital abnormalities of the palate that include cleft palate and hare lip known as?
What are congenital abnormalities of the palate that include cleft palate and hare lip known as?
Which embryonic structure gives rise to the nose, nasal cavity, and primary palate in mammalian embryos?
Which embryonic structure gives rise to the nose, nasal cavity, and primary palate in mammalian embryos?
What is the condition characterized by the failure of the palate to close along the midline?
What is the condition characterized by the failure of the palate to close along the midline?
From which embryonic structure does the tongue derive its rostral two-thirds?
From which embryonic structure does the tongue derive its rostral two-thirds?
From which embryonic structures does the visceral skeleton of the face differentiate in mammalian embryos?
From which embryonic structures does the visceral skeleton of the face differentiate in mammalian embryos?
Where does primary and secondary ossification occur?
Where does primary and secondary ossification occur?
What gives rise to the individual teeth during tooth development?
What gives rise to the individual teeth during tooth development?
Where does the nerve supply sensation to the anterior 2/3 of the tongue originate from?
Where does the nerve supply sensation to the anterior 2/3 of the tongue originate from?
What is responsible for the formation of the outer layer of the tooth or the crown during tooth development?
What is responsible for the formation of the outer layer of the tooth or the crown during tooth development?
Which embryonic structure does the visceral skeleton of the face differentiate from in mammalian embryos?
Which embryonic structure does the visceral skeleton of the face differentiate from in mammalian embryos?
From which part of the body do the dorsal (epaxial) muscles derive during myogenesis?
From which part of the body do the dorsal (epaxial) muscles derive during myogenesis?
During the first period of development, the primordial genital structures are identical in both sexes. This period is referred to as the:
During the first period of development, the primordial genital structures are identical in both sexes. This period is referred to as the:
In mammals, genetic sex is established at fertilization with XY indicating male and XX denoting female. This is part of which stage in sex differentiation?
In mammals, genetic sex is established at fertilization with XY indicating male and XX denoting female. This is part of which stage in sex differentiation?
The development of the sex-specific organs of the genital system is preceded by the formation of a set of temporary undifferentiated structures in the embryo. This period is part of which stage in sex differentiation?
The development of the sex-specific organs of the genital system is preceded by the formation of a set of temporary undifferentiated structures in the embryo. This period is part of which stage in sex differentiation?
Sex differentiation is a complex process that includes distinct sequential stages such as genetic, gonadal, hormonal, phenotypic, and psychological. Which stage involves the physical manifestation of the individual's genetic sex?
Sex differentiation is a complex process that includes distinct sequential stages such as genetic, gonadal, hormonal, phenotypic, and psychological. Which stage involves the physical manifestation of the individual's genetic sex?
In which scenario does the genital tubercle keep growing to generate an elongated phallus or penis?
In which scenario does the genital tubercle keep growing to generate an elongated phallus or penis?
What does the genital tubercle involute and become in the absence of testosterone?
What does the genital tubercle involute and become in the absence of testosterone?
What do the urogenital folds elongate and overgrow in the absence of testosterone?
What do the urogenital folds elongate and overgrow in the absence of testosterone?
What happens to the genital swellings in most domestic mammals in the absence of testosterone?
What happens to the genital swellings in most domestic mammals in the absence of testosterone?
What forms as a result of the separation of the oral and nasal cavities?
What forms as a result of the separation of the oral and nasal cavities?
In which scenario do the urogenital folds beneath the genital tubercle begin to fuse in the midline to form the penile urethra?
In which scenario do the urogenital folds beneath the genital tubercle begin to fuse in the midline to form the penile urethra?
What changes in size as it forms the glans of the clitoris?
What changes in size as it forms the glans of the clitoris?
What changes to form a urogenital groove and later closes to form the penile urethra under the influence of testosterone?
What changes to form a urogenital groove and later closes to form the penile urethra under the influence of testosterone?
Which hormone is responsible for the differentiation of the Wolffian ducts into the epididymides, vas deferens, and seminal vesicles?
Which hormone is responsible for the differentiation of the Wolffian ducts into the epididymides, vas deferens, and seminal vesicles?
What is the main cause of cryptorchidism in dogs?
What is the main cause of cryptorchidism in dogs?
What structure secretes Müllerian inhibiting hormone?
What structure secretes Müllerian inhibiting hormone?
What type of disorder is cryptorchidism in dogs?
What type of disorder is cryptorchidism in dogs?
Where are cryptorchid testicles more prone to problems such as torsion and cancer?
Where are cryptorchid testicles more prone to problems such as torsion and cancer?
What is responsible for causing the mesonephric ducts to thrive in male sexual development?
What is responsible for causing the mesonephric ducts to thrive in male sexual development?
Where should testicular descent be completed before birth in some species?
Where should testicular descent be completed before birth in some species?
What is the consequence of bilateral cryptorchidism in dogs?
What is the consequence of bilateral cryptorchidism in dogs?
How can cryptorchid testicles be identified?
How can cryptorchid testicles be identified?
What is the purpose of neutering in dogs with cryptorchidism?
What is the purpose of neutering in dogs with cryptorchidism?
Which gene is activated in genetically male (XY) embryos, leading to the differentiation of the indifferent gonad into a testis?
Which gene is activated in genetically male (XY) embryos, leading to the differentiation of the indifferent gonad into a testis?
What is the primary hormone responsible for the regression of the Müllerian ducts in male embryos?
What is the primary hormone responsible for the regression of the Müllerian ducts in male embryos?
What triggers the development of male genital ducts and sex-specific external genitalia during embryonic development?
What triggers the development of male genital ducts and sex-specific external genitalia during embryonic development?
What is the first discernible event in the development of the testes during embryonic development?
What is the first discernible event in the development of the testes during embryonic development?
Which cells produce androgen hormone (testosterone) under the influence of the seminiferous cords?
Which cells produce androgen hormone (testosterone) under the influence of the seminiferous cords?
Where do primordial germ cells differentiate and migrate to induce further gonadal development?
Where do primordial germ cells differentiate and migrate to induce further gonadal development?
What is the main hormone produced by fetal Sertoli cells that induces regression of the Müllerian ducts?
What is the main hormone produced by fetal Sertoli cells that induces regression of the Müllerian ducts?
What is the term for the condition characterized by the failure of the palate to close along the midline?
What is the term for the condition characterized by the failure of the palate to close along the midline?
"Brachydactyly" is characterized by what?
"Brachydactyly" is characterized by what?
What does SRY gene activation lead to in genetically male (XY) embryos?
What does SRY gene activation lead to in genetically male (XY) embryos?
What is responsible for inducing regression of Mullerian ducts in male embryos?
What is responsible for inducing regression of Mullerian ducts in male embryos?
When does differentiation of primordial germ cells occur?
When does differentiation of primordial germ cells occur?
Which cells differentiate from primitive interstitial cells in the testis, producing steroids?
Which cells differentiate from primitive interstitial cells in the testis, producing steroids?
What happens to the entire population of oogonia at birth in mammalian ovaries?
What happens to the entire population of oogonia at birth in mammalian ovaries?
What determines the reproductive life of mammals at birth?
What determines the reproductive life of mammals at birth?
What forms the uterine tubes in female genital development?
What forms the uterine tubes in female genital development?
What remains in the joints as articular cartilage and growth plates?
What remains in the joints as articular cartilage and growth plates?
What initiates limb development?
What initiates limb development?
Where are growth plates located in relation to the diaphysis and epiphysis?
Where are growth plates located in relation to the diaphysis and epiphysis?
What separates the oral and nasal cavities during development?
What separates the oral and nasal cavities during development?
What differentiates into odontoblasts during tooth development?
What differentiates into odontoblasts during tooth development?
What gives rise to the individual teeth during tooth development?
What gives rise to the individual teeth during tooth development?
What is responsible for causing the interdigital zones to degenerate in the developing limbs?
What is responsible for causing the interdigital zones to degenerate in the developing limbs?
During the development of male external genitalia, what does the urogenital groove form under the influence of testosterone?
During the development of male external genitalia, what does the urogenital groove form under the influence of testosterone?
In the female scenario, what do the genital swellings become?
In the female scenario, what do the genital swellings become?
What structure forms the glans of the penis under the influence of testosterone?
What structure forms the glans of the penis under the influence of testosterone?
Which part of the female external genitalia becomes the opening of the vulva in the absence of testosterone?
Which part of the female external genitalia becomes the opening of the vulva in the absence of testosterone?
Under the influence of testosterone, what do the urogenital folds elongate and overgrow to become in males?
Under the influence of testosterone, what do the urogenital folds elongate and overgrow to become in males?
What happens to the genital swellings in most domestic mammals in the female scenario?
What happens to the genital swellings in most domestic mammals in the female scenario?
In females, what do the unfused urogenital folds beneath the genital tubercle form?
In females, what do the unfused urogenital folds beneath the genital tubercle form?
What forms as a result of the separation of the oral and nasal cavities during development?
What forms as a result of the separation of the oral and nasal cavities during development?
What forms as a result of midline fusion in males that initially remains separate in females?
What forms as a result of midline fusion in males that initially remains separate in females?
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Study Notes
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The epiphyseal plate, the cartilage between primary and secondary ossification centres, allows bone growth in length.
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The growth in diameter of bones occurs by bone deposition beneath the periosteum.
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Joint development: mesenchyme between bones forms an interzone region, which develops into fibrous, cartilaginous, or synovial joints depending on the future joint type.
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Synovial joint formation: mesenchyme in the interzone cavitates to form the synovial cavity, which is then surrounded by the synovial membrane and synovial folds.
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Joint development: interzone mesenchyme forms intra-articular ligaments and the perichondral tissue surrounding the interzone forms the joint capsule, which gives rise to ligaments.
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Proper synovial joint development requires nerve-driven muscle activity and joint movement to prevent ankylosis.
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Vertebrae development begins with mesenchyme cells around the notochord, which differentiate into hyaline cartilage models that ossify through endochondral ossification.
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Vertebrae development: sclerotomes split and differentiate into cranial and caudal regions to form a cartilage model of one vertebra by the combination of the caudal half of one sclerotome with the cephalic part of the adjacent sclerotome.
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Vertebrae development: mesenchyme forms the vertebral arch, which encloses the neural tube, and the transverse and costal processes, which eventually form the ribs.
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Intervertebral disc regions develop between newly formed adjacent vertebrae, with the mesenchyme forming the annulus fibrosus and the persisting notochord as the nucleus pulposus.
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Ribs develop as part of the cartilage model for each vertebra, but the costal processes separate and the cartilage model ossifies except for the anterior portion, which remains as costal cartilage.
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Sternum forms as paired hyaline cartilage models on either side of the anterior midline, which later fuse and undergo endochondral ossification to form sternebrae.
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Limbs develop as limb buds, which are produced by localised proliferation and condensation of parietal mesenchyme covered by the ectoderm.
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The skull consists of two parts: the neurocranium (protective cranial vault) and the viscerocranium (facial skeleton).
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The nasal cavity develops from the frontonasal prominence, which expands and divides into the frontal bone and the nasal processes.
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The medial and lateral nasal processes form the nose, nasal cavity, and primary palate, and the growth of the nasal placodes leads to the formation of the nasal pits and primitive nasal cavity.
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The palate forms as the nasal and oral cavities are separated by the development of the primary palate and the subsequent growth of the secondary palate.
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The palate, including the fusion of the primary and secondary palate, leads to the separation of the oral and nasal cavities.
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Congenital abnormalities of the palate include cleft palate and cheiloschisis (hare lip).
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Cleft palate is a failure of the palate to close along the midline and can be inherited or caused by exposure to a teratogen.
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Clefts can affect the lip, alveolar process, entire extension of the primary palate, or soft and hard palate.
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The oral cavity develops as a consequence of the formation of the upper and lower jaw.
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The tongue develops from several swellings on the floor of the pharynx, with the rostral two-thirds originating from the first branchial arch and the caudal third from the second branchial arch.
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The skull consists of two parts: the neurocranium (protective cranial vault) and the viscerocranium (facial skeleton).
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The nasal cavity develops from the frontonasal prominence, which expands and divides into the frontal bone and the nasal processes.
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The medial and lateral nasal processes form the nose, nasal cavity, and primary palate, and the growth of the nasal placodes leads to the formation of the nasal pits and primitive nasal cavity.
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The palate forms as the nasal and oral cavities are separated by the development of the primary palate and the subsequent growth of the secondary palate.
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The palate, including the fusion of the primary and secondary palate, leads to the separation of the oral and nasal cavities.
-
Congenital abnormalities of the palate include cleft palate and cheiloschisis (hare lip).
-
Cleft palate is a failure of the palate to close along the midline and can be inherited or caused by exposure to a teratogen.
-
Clefts can affect the lip, alveolar process, entire extension of the primary palate, or soft and hard palate.
-
The oral cavity develops as a consequence of the formation of the upper and lower jaw.
-
The tongue develops from several swellings on the floor of the pharynx, with the rostral two-thirds originating from the first branchial arch and the caudal third from the second branchial arch.
-
The skull consists of two parts: the neurocranium (protective cranial vault) and the viscerocranium (facial skeleton).
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The nasal cavity develops from the frontonasal prominence, which expands and divides into the frontal bone and the nasal processes.
-
The medial and lateral nasal processes form the nose, nasal cavity, and primary palate, and the growth of the nasal placodes leads to the formation of the nasal pits and primitive nasal cavity.
-
The palate forms as the nasal and oral cavities are separated by the development of the primary palate and the subsequent growth of the secondary palate.
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The palate, including the fusion of the primary and secondary palate, leads to the separation of the oral and nasal cavities.
-
Congenital abnormalities of the palate include cleft palate and cheiloschisis (hare lip).
-
Cleft palate is a failure of the palate to close along the midline and can be inherited or caused by exposure to a teratogen.
-
Clefts can affect the lip, alveolar process, entire extension of the primary palate, or soft and hard palate.
-
The oral cavity develops as a consequence of the formation of the upper and lower jaw.
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The tongue develops from several swellings on the floor of the pharynx, with the rostral two-thirds originating from the first branchial arch and the caudal third from the second branchial arch.
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In the testis, Sertoli cells proliferate, forming cordlike structures (seminiferous tubules) around primitive germ cells. Leydig cells differentiate from primitive interstitial cells, producing steroids.
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In the absence of a Y chromosome (female embryos with two X chromosomes), the primordial gonadal cords stop growing and become disorganized. Ovarian differentiation begins.
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In the central region of the ovary, the sex cords disappear, forming the ovarian medulla. In the cortical region, gonadal cords remain, forming primordial follicles.
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Female primordial germinal cells differentiate into oogonia, undergoing mitotic activity. These, along with supporting cells, form primordial follicles.
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The entire population of oogonia enters the first meiotic division but stops at the prophase stage.
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At birth, mammalian ovaries contain a reserve of primordial follicles. The number of these follicles (follicular reserve) determines reproductive life.
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During puberty, some follicles develop, secrete hormones, and either regress or ovulate.
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Female genital development is the default pathway. The paramesonephric (Müllerian) ducts form the female genital tract without hormonal requirement.
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The cranial part of the paramesonephric ducts forms the uterine tubes, the middle portion becomes the uterine horns, and the caudal portion becomes the uterus, cervix, and cranial vagina.
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Length of the paramesonephric ducts that become fused varies among species. In humans and primates, the uterus has no horns. In rodents and rabbits, there is a double uterus. In monotremes and marsupials, there are two vaginas.
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Remnants of the embryonic mesonephric ducts can be found in the vaginal vestibule in females (Gartner's duct).
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In embryos, both sexes have primordia of male and female genital ducts (mesonephric and paramesonephric ducts).
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Male genital development depends on testicular hormones. Female genital development is predetermined in the absence of testicular influence, but recent evidence suggests some level of female genital development is not completely passive.
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