EMBRYO Flashcards
What is isometric growth?
Shape preserved; growth at the same rate.
What is allometric growth?
Growth not occurring at the same rate.
What happens in the 5th week of embryo development?
Migration of cells to gonadal ridges; indifferent/primal gonad formation.
What is fertilization?
Sperm + oocyte → zygote.
What are teratomas?
Tumors arising from migratory cells, appearing between 3-8 weeks.
What are gametes derived from?
Primordial germ cells (PGCs) in the epiblast.
What is gametogenesis?
Process of meiosis and mitosis leading to the formation of gametes.
What is the process of oogenesis?
PGCs in gonad differentiate into oocytes through mitotic divisions.
What is a primary oocyte?
Germ cell that undergoes meiosis, resulting in arrested development at diplotene stage.
At birth, how many primary oocytes are present?
Approximately 600,000.
What occurs during puberty in female development?
15-20 follicles begin to mature each month.
What is a primordial follicle?
Structure containing primary oocyte surrounded by flat epithelial cells.
What is the zona pellucida?
Layer of glycoproteins surrounding the oocyte.
What triggers ovulation?
Uterine thickening and hormonal changes (estrogens, LH, FSH).
What is the corpus luteum?
Structure formed from follicle post-ovulation that secretes hormones.
What happens if there is no pregnancy?
Corpus luteum degenerates and forms corpus albicans.
What is spermatogenesis?
Process of developing spermatozoa from spermatogonia starting at puberty.
What are Sertoli cells?
Supporting cells in seminiferous tubules that assist in spermatogenesis.
What is the role of LH in spermatogenesis?
Stimulates testosterone production from Leydig cells.
What is spermiogenesis?
Transformation of spermatids into spermatozoa.
What occurs during the acrosome reaction?
Formation of enzymes necessary for penetration of the oocyte.
What is the significance of cytoplasmic bridges in spermatogenesis?
They allow for synchronized development of spermatogenic cells.
Fill in the blank: The _______ is the protective layer surrounding the oocyte.
zona pellucida.
True or False: The primary oocyte completes meiosis before birth.
False.
How many sperm cells are produced daily?
300 million
Sperm cells are formed in the lumen of seminiferous tubules.
What is the lifespan of sperm cells?
30 days
Sperm cells are produced over 60/75 days and transported in 10-14 days.
What is the typical range of sperm per ejaculate?
20 to 100 million
This range indicates the variability in sperm count across different individuals.
What are the stages of spermatogenesis?
Stage 1: Type A (Mitosis) → Type B → Primary Spermatocytes
Stage 2: Meiosis (2n → n) → Prophase Meiosis
Stage 3: Secondary Spermatocytes
Stage 4: Early Spermatids
Stage 5: Elongated Spermatids
Stage 6: Spermatozoa
Each stage involves specific cellular changes and processes leading to the formation of mature sperm.
What do Leydig cells release?
Androgens, testosterone, androstenedione, DHEA
Leydig cells are stimulated by LH to produce these hormones.
What is the role of Sertoli cells?
Support development, form blood-testis barrier, phagocytosis
Sertoli cells also produce proteins like AMH and inhibin.
What is the Golgi phase in spermatogenesis?
Formation of new spherical sperm with developed Golgi, proacrosomic granules, and centrioles
This phase is crucial for the initial development of sperm.
What occurs during the acrosomal phase?
Nucleus elongates, acrosome covers anterior part of the nucleus
The manchette forms the postnuclear cap and the mitochondria assemble around the flagellum.
What is capacitation in sperm?
Removal of seminal plasma coatings and surface molecules
This process is necessary for sperm to penetrate the zona pellucida.
What happens during the acrosome reaction?
Release of enzymes to penetrate the zona pellucida
Enzymes like acrosin and trypsin-like substances are released during this reaction.
What are the steps in fertilization?
- Penetration of corona radiata
- Penetration of zona pellucida
- Fusion of oocyte and sperm
Only one sperm typically fertilizes the egg after passing through these barriers.
What triggers the cortical reaction after fertilization?
Release of lysosomal enzymes from cortical granules
This reaction makes the zona pellucida impenetrable to additional sperm.
What is the result of the fusion of sperm and egg nuclei?
Formation of a diploid zygote
The zygote contains 23 maternal and 23 paternal chromosomes.
What is the significance of the cleavage stage in embryonic development?
Initiation of mitotic divisions resulting in blastomeres
This process continues until a compacted morula is formed.
What happens to the inner cell mass during blastocyst formation?
It becomes the embryoblast
The outer cell mass becomes the trophoblast, which is essential for implantation.
What initiates implantation in the uterus?
Loss of zona pellucida
Trophoblastic and endometrial interactions facilitate implantation.
What are selectins and integrins involved in?
Trophoblastic and endometrial action during implantation
They are crucial for the adhesion process in implantation.
What are embryonic cells described as in the context of differentiation?
PLURIPOTENT
This term indicates the pluripotent nature of embryonic cells, which can give rise to various cell types.
What are the two types of signaling involved in embryo differentiation?
Autocrine and paracrine signaling
These signaling pathways are crucial for the communication between cells during development.
What role does activin play in embryonic development?
Prevents upregulation of certain processes
Activin is involved in regulating cellular processes during differentiation.
What hormonal changes occur in the corpus luteum during the preparation for implantation?
Estrogen and progesterone
These hormones are essential for preparing the uterine lining for embryo implantation.
What must trophoblasts bind to in the uterine environment?
L-selectin
Binding to L-selectin is critical for the adhesion of trophoblasts to the endometrium.
Identify the phases of the menstrual cycle.
- Follicular phase
- Ovulation
- Luteal phase
- Menstrual phase
Each phase is characterized by specific hormonal changes and physiological events.
What are the two layers of trophoblast?
- Cytotrophoblast (inner layer)
- Syncytiotrophoblast (outer layer)
These layers play distinct roles in implantation and nutrient exchange.
What is the structure formed from the hypoblast and what is its role?
Primitive yolk sac
It serves as an early source of nourishment for the developing embryo.
What is the significance of the blastocyst stage?
It is when the embryo embeds itself in the endometrium
This stage is crucial for establishing pregnancy.
What does gastrulation lead to in embryonic development?
Formation of germ layers
These layers are ectoderm, mesoderm, and endoderm, which will differentiate into various tissues.
Fill in the blank: The _______ is the outer layer that forms the skin and nervous system.
Ectoderm
Ectoderm is responsible for forming skin, hair, nails, and the nervous system.
True or False: The mesoderm develops into the digestive and respiratory tracts.
False
The endoderm is responsible for developing into the digestive and respiratory tracts.
What is the role of the notochord during development?
It serves as a basis for the axial skeleton
The notochord is a key structure in the development of vertebrates.
Describe the process of neurulation.
Formation of the neural tube from the ectoderm
Neurulation is a critical step in the development of the nervous system.
What is the significance of the primitive streak in embryonic development?
It marks the site of cell migration and differentiation
The primitive streak is essential for establishing the body axis and germ layer formation.
What are somites and what do they develop into?
Segments of mesoderm that develop into muscles and skeleton
Somites play a crucial role in the segmentation of the body plan.
What happens to the trophoblast during early development?
It rapidly proliferates to form primary villi
This proliferation is important for establishing blood supply to the embryo.
What is the connection between the amniotic sac and the developing fetus?
It provides protection and cushioning
The amniotic sac is filled with amniotic fluid, which protects the fetus.
What structures are derived from the ectoderm
Skin, hair, nose, mouth, nervous system
Significance cloaca
Common cavity for hind gut and urogenital sinus, later separating into distinct regions
What is the gut tube and its significance
The gut tube is formed from endoderm and mesoderm, giving rise to digestive and respiratory systems
What strictures are derived from the foregut
Esophagus, trachea, stomach, liver, pancreas, biliary apparatus
What is the role of the vitelline duct
Connects the yolk sac to primitive intestine and later becomes part of the umbilical cord
What structures are formed during primitive circulation?
Development of vessels like aortic sac, vitelline arteries and umbilical veins
What is the neural cred and its significance
It’s formed when cells detach from neural fold during neural tube closure, contribution to PNS and other structures
What marks the completion of neurulation
It’s completed when the neural tube is fully fused allowing communication with minority cavity though neuropores
Derivatives endoderm
Digestive tract, respiratory tract, liver, pancreas
What is the role of the neural tube in the nervous system
Precursor CNS forming a closed tubular structure with brain vesicles
What is the significance of neural plate
The neural plate forms during third week of development and it’s the precursor of neural tube closure
What is the significance of neural plate
The neural plate forms during third week of development and it’s the precursor of neural tube
What are somites and their differentiation
Somites differentiate into sclerotome (cartilage and bone), myotome (muscle tissue) and dermatomes (dermis and skin)
Mechanisms regulating somitge formation
Clock and wavefront model determining absolute position along the axis
Structures arising from intermediate mesoderm
Urogenital structures as kidneys and gonads
What is the role of BMPs, WNTs and SHH in mesoderm differentiation?
Signaling molecules inducing differentiation in mesodermal tissues
What is the primary heart field
Heart progenitor cells specified by lateral pathways contributing to right ventricle and other structures
What is cardiac looping
Shaping heart tube in final structure in 4th week
What structures are derived from the midgut
Small intestine, cecum, appendix, ascending colon and part of the transverse colon
What structures are derived from the hind gut
Descending colon, rectum and upper part anal canal
What is the role of RA in gut development
Specifies different regions of the gut tube influencing differentiation
What are the stages of respiratory system development
Pseudoglandular weeks 6-16
Canalicular 16-28
Saccular 28-36 leading to alveoli formation
What structures were derived from endoderm in the respiratory system
Mucosal lining and epithelial cells alveoli
What structures are derived from the mesoderm in respiratory system
Muscle, cartilage and visceral pleura
Role of pleuropericardial membranes
Separate the pleural cavities from pericardial cavity
What is the axial skeleton and components
Skull, vertebral column, ribs, sternum all derived from mesenchyme
What is intramemebranous ossification
Mesenchymal cell condensation and differentiation into osteoblasts forming flat bones
What abnormalities can occur in axial skeleton development
Spina bifida, cranioschisis and anencephaly
What is the apical ectodermal ridge AER
Structure that regulated limb bud outgrowth and digital formation
What is the role of SHH in limb development
Influences anterior-posterior patterning and identity
Stages limb development
Formation limb buds
Digit formation
Differentiation skeletal and muscular structures
Significance neural crest in skeletal development
Formation facial cartilage and bones
Role of diaphragm in body cavity formation
Divides thoracic and peritoneal cavities aiding separation body cavities
Significance pleural cavities
House lungs and expand during development x accommodate growth
Role mesenchymal tissue in bone formation
Differentiates in osteoblasts forming periosteum and contributing to mineralization
Significance secondary palate
Forms from palatial shelves separating oral and nasal cavities
Abnormalities in facial development
Cleft palate and improper fusion facial tissues
Role box genes in limb development
Regulation identity and order digits
Significance splanchnic mesoderm in organ development
Formation connective tissue and stroma in organs like pancreas
Role neural tube in axial skeleton development
Signals for differentiation of somites and skeletal structures
Significance primitive streak
Initiates gastrulation and establishes body axis
Role connecting stalk
Forms umbilical cord, facilitates nutrient and waste exchange
Significance endocardial cushions
Formation heart valves and septa
Role yolk sac in hematopoietis
Initial site hematopoiesis forming blood islands and hemangioblasts
Significance hepatic diverticulum
Gives rise to liver and biliary passages
Role mesogastrium in spleen development
Mesenchymal cells that coalesce to form the spleen
What does differentiation involve during embryonic development
Progression from zygote to blastocyst to gastrula leading to specialized cells forming tissues and organs
3 layers gastrula and their contributions
Ectoderm= nervous system, sensory organs
Mesoderm= muscles, bones, blood, reproductive organs
Endoderm= digestive tract lining, respiratory system, endocrine glands
Part of human spermatozoon
Head= acrosome, galea cavities
Neck= anterior and posterior end knobs
Body= spiral fibers, axial thread
Tail= main segment, terminal filament
Morphogenesis
Process responsible for development of complex shapes of adults from cells derived from fertilized egg
Difference differentiation and morphogenesis
Differentiation= specialized cells forming tissues types
Morphogenesis shapes organism structure
French flag model
How cell differentiate bases on morphogen concentration gradients
How does zone of polarizing activity influence limb formation
Produces shh creating gradient determining limb formation with the thumb forming at low shh and little finger at high levels
Hox genes
Specify body plans invertebrates and vertebrates, determine arrangement body segments
Reaction diffusion model in morphogenesis
Predicts alternating area of high and low concentrations of substances, instructing cells to differentiate based on threshold levels
Positional information in development
Defined by morphogen gradients, guiding cells to differentiate according to their location
Rolemorphogens in development
Chemical substances that react and diffuse though tissues creating patterns and structures during development
