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Title: Embryology
Description: Notes on embryology from an Anatomy and Physiology module.
Description: Notes on embryology from an Anatomy and Physiology module.
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Embryology **
Embryology is a subdivision of developmental anatomy, which concerns
developmental changes that occur before birth and helps to explain birth defects
...
The head of a sperm contains:
- Acrosome – a sack of digestive enzymes that includes phospholipase
...
o Produced by the Golgi apparatus
- Haploid nucleus – bears 23 chromosomes
...
The middle of a sperm contains:
- Mitochondria spiraled tightly around the contractile filaments of the tail
...
The tail of a sperm is a typical flagellum produced by a centriole
...
Prostate gland
The prostate gland produces the fluid in which sperm swims:
- Semen (UK) – Seminal fluid (US)
- Contains prostaglandins
o Causes pain and swelling
o Trigger smooth muscle contraction
§ Triggers the uterus to contract
• Moves sperm up towards and into the cervix
Oz/os = aperture of cervix
1
...
- Surrounded by much smaller cells – cumulus cells
o Makes ‘halo’ around the egg – corona radiata
o Densely packed
2
...
When the sperm makes contact with the zona pellucida, blocking factors are
produced, stopping any other sperm cells making contact with the oocyte
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It becomes an unviable embryo and won’t fully develop
...
Prenatal development – the development in the uterus
-
From conception to birth
Split into three stages
o The germinal period
§ The first two weeks of development
§ Result in formation of the primitive germinal layers
o The embryonic period
§ From the second to the end of the eighth week
...
If there were any birth defects, they would usually occur in the first 8 weeks
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o 2 cells divide to form 4, 8, 16 etc
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o Fairly unstable – cells can break off
§ This is how identical twins are made
o They are useful in fertility clinics due to being so easy to break apart
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Women produce progesterone during pregnancy
o Produces uterine milk – a sticky mucous
§ A sticky substance that coats the lining of the womb
§ The sticky material helps to adhere the blastocyst and
endometrium
...
• The endoderm – forms the inner part of the embryonic
disc
...
Cells from the ectoderm divide rapidly and form a thickening termed the primitive
streak
...
This means the two-layered embryonic disc has now become a
three-layered embryo
...
Ectoderm
Mesoderm
Endoderm
Tri-laminar
embryo
Every single part of the body originates from one of these three layers
...
- By the end of week 8 – all organ systems are recognisable
- Ectoderm
o Develops into the central nervous system and epidermis of the skin
(outer layer of skin)
...
- Endoderm
o Develops into the gastrointestinal tract and epithelial linings of the hollow
organs and respiratory system
...
When stem cells are cultured in the presence of the correct growth factors, they
can be encouraged to differentiate into any tissue
...
-
-
Neurulation – the first event of organogenesis gives rise to the brain and spinal
cord
...
The neural plate folds inward as a neural groove with prominent neural folds
...
o For the tube to close, the mother needs plenty of vitamin B9 – folic acid
...
The anterior end becomes the brain; the rest becomes the spinal cord
...
g
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Congenital – Developmental defects that are more difficult to predict
- They occur when human development goes wrong – abnormal embryonic
development
...
- Well known teratogens include; ionizing radiations, noxious chemicals, alcohol,
ethanol, rubella, and certain drugs (e
...
thalidomide and certain infectious
diseases)
...
- Common congenital defects example:
o Septal defects in the heart (such as hole in the heart) and cleft palate
...
- The mother’s immune system is continuously screening for both genetic and
congenital defects throughout pregnancy
...
It is the failure of closure of the neural tube (in
weeks 3-4) resulting in exposed neural tissue
...
The three major types of spina bifida are:
- Spina bifida occulta
- Meningocele
- Myelomeningocele
Spina bifida occulta (hidden spina bifida)
- It is a failure of one or more of the vertebrae to close correctly during the
formation of the vertebral column
...
Meningocele
- The meninges (protective coverings of the central nervous system) protrude
through the space between the two vertebrae, resulting in the formation of a fluid
filled cyst
...
- It can be removed easily
...
Myelomeningocele
- The most common form of spina bifida
- It is often associated with major complications
- It involves the unclosed neural tube (spinal cord) and surrounding meninges
protruding out through the vertebral column
...
Anencephaly
In anencephaly, the cerebrum and part of the brain stem never develop, presumably
because the neural folds fail to fuse rostrally
...
Muscles are flaccid, and no voluntary
movement is possible
...
Death occurs soon
after birth
...
Hydrocephalus
-
Cerebrospinal fluid produced in the ventricles in brain
...
It is often linked in to spina bifida
...
The respiratory system develops from little bulge (buds) on the gut
...
o If there is no separation – tracheo-oesophageal Fistula (fistula =
abnormal connection between two organs)
§ The leading cause of pneumonia in babies
...
o Quite a simple surgical procedure to correct
...
Adult infections may be asymptomatic
...
o Although, it can cross the placenta and interfere dramatically with human
development
Symptoms for the baby include; hearing loss, cerebral palsy, microcephaly,
mental retardation, visual defects and dental anomalies
...
Another 50-70% of such babies may suffer from foetal alcohol effects (FAE), which is
milder than FAS
...
) are also possible
...
Children with FAS fail to thrive, have mild to moderate mental retardation and
behaviour problems
...
Thalidomide
-
In wide use in the UK
...
It was the ‘wonder drug’ of the 1960s developed to treat morning sickness
...
It interferes with the development of ‘limb buds’ early on in pregnancy, resulting
in abnormally short arms and legs
...
It is now being tested as an effective treatment of cancer, particularly lung
cancer
Title: Embryology
Description: Notes on embryology from an Anatomy and Physiology module.
Description: Notes on embryology from an Anatomy and Physiology module.