Transcript RAD 460 – Cross-Sectional Anatomy Lesson I

Cross-Sectional Anatomy
Lesson I
Human Development
• Fertilization of the ovum occurs in the fallopian
tubes
• After fertilization, the united sperm and ovum
(zygote) travel into the uterus
• Major cellular events occur in the uterus, one of
the events being the formation of a blastocyst
which is implanted in the uterine wall
(Endometrial Layer)
• Implantation occurs approximately seven (7)
days after ovulation or around the twenty-first
(day 21) of the menstrual cycle.
• Implantation occurs as the endometrial tissue
grows and surrounds the blastocyst (takes
about 7 days)
Human Development
• HCG secreted by the blastocyst
keeps it from being aborted
• HCG- Human Chorionic
Gonadotropin secretion is only
produced in pregnant women
• Pregnancy tests are based on the
presence of this hormone in blood
or urine
Formation of
Primary Germ Layers
• During implantation, changes occur in the
inner cell mass of the blastocyst, resulting in
the formation of the primary germ layers
• Amnionic cavity develops in the inner cell
mass
• Two layered flattened embryonic disk develops
• Ectoderm, endoderm, and mesoderm develop
• ALL TISSUES AND ORGANS DEVELOP FROM
THESE THREE PRIMARY GERM LAYERS
• Embryonic stage of development begins,
lasting 6 weeks (from beginning of week three
thru week eight)
Development of the
Human Brain
• CNS (brain and spinal cord) develops from
a thickened area of the embryonic
ectoderm called the neural plate
• 18 – 20 days after conception
• Neural plate is altered to form a neural tube
and neural crest
• Neural tube forms the brain and spinal cord
• Neural crest forms most structures within
the peripheral nervous system
Neural Tube
• Temporarily open at both caudal and cranial
ends (portions)
• Cranial portion closes approximately 24
days after conception
• Caudal portion closed about 2 days later
• Differentiation and growth of the neural tube
is greatest at the cranial end
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Neural Tube Development
Four weeks after conception –
cranial end differentiates into three
primary vesicles;
– Prosencephalon (forebrain)
– Mesencephalon (midbrain)
– Rhombencephalon (hindbrain)
Further Differentiation of the
Neural Tube Divisions
During the next week:
–Prosencephalon (forebrain) =
telencephalon and diencephalon
–Rhomencephalon (hindbrain) =
metencephalon and
myelencephalon
– 3 now equal 5
Ectoderm
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Epidermis of the skin
Hair, nails, skin glands
Lens of the eye
Enamel of the teeth
All nervous tissue
Adrenal medulla
Sense organ receptor cells
Linings of the oral and nasal cavities,
vagina, and anal canal
Endoderm
• Epithelial lining of digestive tract
• Epithelium of the liver and
pancreas
• Epithelium of urinary bladder &
urethra
• Epithelium of the respiratory tract
• Thyroid, parathyroid, and thymus
glands
Mesoderm
• Dermis of the skin
• Skeletal, smooth, cardiac muscle
• Connective tissue including cartilage and
bone
• Epithelium of serous membranes
• Epithelium of joint cavities
• Epithelium of blood vessels
• Kidneys and ureters
• Adrenal cortex
• Epithelium of gonads and reproductive ducts
Fetal Images
Fetal Images
The Brain
• Weighs about 3 lbs.(2% of body weight)
• Larger in the male than in the female
• Composed of organized regions of gray
and white matter
• Gray matter = nerve cell bodies and
unmyelinated fibers (regions of synapse
–electrical communication between
neurons)
• Gray matter grouping = Basal Ganglia
• White matter = nerve fibers covered in
myelin (fatty substance)
Basal Ganglia
Regions of the Brain
• Cerebrum
• Diencephalon
• Brainstem
• Cerebellum
Brain Regions