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88 Cards in this Set
- Front
- Back
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When is the embryonic period?
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Beginning of 3rd week to end of 8th week
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What happens during weeks 1-2?
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Egg forms, develops and implants
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When is the fetal period?
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9 to 38 weeks
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What are gametes?
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Sexual germ cells (sperm, ovum)
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Where does fertilization occur?
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uterine tube (fallopian tube)
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When does fertilization occur?
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Usually 12-24 hours after ovulation
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What is a zygote?
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Fertilized egg
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When does mitosis begin?
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Shortly after zygote formation
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what is another term for mitotic division?
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clevage
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What is a morula?
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12-16 cells
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When does the morula form?
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about 3rd day after fertilization
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what is a blastocyst?
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a thin-walled hollow structure that contains a cluster of inner and outer cells
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what are trophoblasts?
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cells on outer edge of embryo
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When does implantation of the blastocyst occur?
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begins at 5-7 days and complete by 10th day
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What do trophoblasts form?
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placenta
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Cells in inner mass of blastocyst become ___?
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embryo
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What occurs after blastocyst has been implanted?
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Cell differentiation
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What is cell differentiation?
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Cells become different types of cells called primary germ layers
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What are the three layers of primary germ layers?
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Ectoderm (upper/outer); mesoderm (middle); endoderm (lower/inner)
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What does ectoderm form? (6)
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epidermis of skin; teeth; nervous system; hair; nails; epithelial tissue
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What does mesoderm form? (4)
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Connective tissue (bones; muscles; blood vessels; cartilages)
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What does endoderm form? (2)
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epithelial lining of digestive tract and respiratory tract
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When does the primitive streak form?
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Week 3
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What is the purpose of the primitive streak?
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establishes a structural foundation for change along the longitudinal axis
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What is Hensen's node?
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small area of proliferating cells
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What is the neural plate?
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thickening that grows upward to form the neural fold
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What is the notochord?
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strip of cells along the midline (becomes primitive skeleton)
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How is neural tube formed?
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Neural folds meet at midline and fuse. Gives rise to CNS
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From what does the CNS form?
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Neural tube
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What are somites?
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resemble the vertebral column
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When do somites appear?
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16th day
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What 3 groups do the somites differentiate into?
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sclerotome; myotome; dermotome
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What is the sclerotome and what does it become? (3)
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Innermost part of a somite. Vertebrae; intervertebral discs; ribs
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what is another name for myotome?
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myomere
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What is the myomere?
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myotome
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Where is the myotome?
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lateral to the sclerotome
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What does the myotome become?
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musculature of the trunk
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What is the dermatome and where?
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become dermis; most lateral portion of somite
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When does flexion of the embryo begin?
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end of 3rd week
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What occurs during the 3rd week?
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flexion of the embryo
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What happens during flexion?
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rapid growth causes embryo to buckle resulting in a series of folds; become cylindrical in shape
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What are the characteristics of the prosencephalon during 3rd week of embryonic development?
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Smooth, undifferentiated bulge at top of embryo (aka forebrain)
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What is the stomodeum?
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Oral groove (primitive mouth)
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What are the branchial arches?
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series of transverse elevations and depressions which grow together at the midline. ( arches but only 4 visible)
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What is the 1st branchial arch?
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Mandibular arch
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What does the 1st branchial arch form? (6)
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Lower lip; muscles of mastication; mandible; anterior portion of the tongue; some structures of the middle ear
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What is the 2nd branchial arch?
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Hyoid arch
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What does 2nd branchial arch form? (3)
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Upper body and lesser horns of the hyoid; stapes; muscles of facial expression
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Do branchial arches 3 to 6 have names?
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No. number only
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What does third arch form?
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Lower body of the hyoid bone; posterior portion of tongue
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What do the 4th and 5th branchial arches form?
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cricoid and arytenoid cartilages; cartilages of trachea
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What does the caudal arch form?
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palatine muscles; pharyngeal constrictors
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What happens in the 4th week of development? (6)
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nasal (olfactory) placodes; nasal pits; hyoid arches; leg and arm buds; otic pit; umbilical cord
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What happens in 5th week of development? (3)
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Face divides into 4 primordial areas; heart beat; respiratory system begins to develop
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What are the 4 primordial areas of the face?
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frontonasal process; maxillary process; mandibular arch; hyoid arch
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What happens in 6th week of development? (9)
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palate begins to form; nasal laminae; nasal septum; eyes; mouth; tongue; ears; fingers; elbows and knees
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How is the primary palate formed?
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Shelf formed by the fusion of maxillary and medial nasal processes
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What forms nasal laminae?
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2 plates formed by fusion of maxillary and medial nasal processes
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What forms nasal septum?
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fusion of nasal laminae
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What happens in 7th week of development?
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Nasal area narrows; eyes move anterior to surface of face; tooth buds; organ systems essentially complete; length 30 mm (1 inch); limbs and fingers elongate
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what is an important time in the formation of the palate?
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6th - 7th week
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What happens in week 8?
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embryo becomes fetus; has all essential parts
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When does palate form?
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5th week to end of facial completion
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Development of forebrain?
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Forebrain ->
Central frontal prominence -> frontonasal process -> medial nasal process and lateral nasal process (sides of nose and upper cheek) |
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What does lateral nasal process become?
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sides of nose and upper cheek
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What does medial nasal process become?
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center setion of nose, nasal septum, philtrum, center of upper lip and alveolar ridge, and premaxilla
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Primary palate
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tissue formed from the fusion of the maxillary and medial nasal processes. forms a partial division of stomodeum into an upper and lower cavity
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When does the primary palate fuse?
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5th - 6th week
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What does the primary palate develop into?
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upper lip and philtrum;
upper 4 central and lateral incisors and alveolar ridge; premaxilla bone; anterior nasal septum |
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Secondary palate
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palate closes from incisive foramen to the uvula forming hard and soft palates
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when does hard palate fuse?
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6th-10th week
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when does soft palate fuse?
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10-12th week
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neural plate
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thickening that forms the neural tube
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What does the nervous system derive from?
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ectoderm
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Describe development of nervous system
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2nd week:
neural plate, neural groove, neural folds, neural tube 3rd week: neural crest |
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What is another term for neural crest?
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ganglion ridge
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What is the ganglion ridge?
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neural crest. ridge of ectodermal cells on either side of the neural tube
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What does the neural crest become?
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spinal and cranial nerve ganglia; ganglia of sympathetic and autonomic nervous system
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Describe development of the spinal cord?
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6th week:
sulcus limitans alar and basal plates 9th week: posterior, anterior and lateral horns of gray matter |
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What is the sulcus limitans?
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groove formed from thickening of lateral walls
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Where are the alar plates?
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dorsal to sulcus limitans
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Where are the basal plates?
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ventral to sulcus limitans
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Describe development of brain?
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4th week:
pros-, mes-, rhombencephalon 5th week: tel-, di-, mes-, met-, myelencephalon |
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What walls and cavities are found in the telencephalon?
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cerebral hemisphere, lateral ventricles
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What walls and cavities are found in the diencephalon?
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thalamus, hypothalamus, third ventricle
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What walls and cavities are found in the mesencephalon?
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midbrain, aqueduct
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What walls and cavities are found in the metencephalon?
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pons, cerebellum, upper portion of 4th ventricle
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What walls and cavities are found in the myelencephalon?
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medulla oblongata, lower portion of ventricle
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