LO :
1. General embryological stages of human
a. Tahap Fertilisasi
Fertilisasi merupakan proses penyatuan inti sel gamet jantan (sperma) dengan inti sel gamet betina
(ovum).
b. Tahap Pembelahan (Cleavage)
Tak lama setelah terbentuk zigot, sel ini akan langsung beranjak ke tahap pembelahan membentuk
banyak sel. Pembelahan yang berlangsung ialah pembelahan mitosis yang berlangsung sangat cepat
diawli dengan pembelahan dua sel, empat sel, delapan sel, dan seterusnya sampai terbentuk morula
(tahap 32 sel). Pembelahan mitosis yang berlangsung pada zigot tidak diikuti dengan pembelahan
sitoplasma (sitokinensis), hanya pembelahan inti saja.
c. Tahap Blastulasi
Tahap blastulasi ialah tahap pembentukan blastula (bola berongga) dari morula (bola padat). Pada
tahap sebelumnya zigot membelah membentuk banyak sel (sampai 32) yang disebut morula.
Kemudian tiap – tiap sel akan terus melanjutkan tahapan pembelahan hingga mencapai angka 64
sampai 100 sel. Yang membedakan tahap morula dengan blastula ialah jumlah sel dan terdapatnya
rongga pada tahap blastula yang disebut blastosol.
Rongga blastosol berisikan yolk atau kuning telur sebagai satu – satunya sumber makanan bagi sel
– sel blastula untuk tumbuuh dan berkembang. Pada tahap ini (blastula), embrio akan masuk
(implantasi) ke dalam uterus (rahim) induk betina.
Selanjutnya tahap hubungan induk betina dengan embrio akan terjalin melalui pembentukan selaput
ekstraembrionik dari dinding endometrium induk betina. Segala kebutuhan embrio akan terpenuhi
oleh induk betina melalui hubungan yang terbentuk dalam selaput embrionik (plasenta, amnion,
korion, dan alantois) sampai masa pertumbuhan dan perkembangan embrio selesai. Keberadaan
embrio di dalam endometrium induk betina akan menghasilkan hormon HCG (Human Chorionic
Gonadothropin) yang merangsang induk betina untuk mensekresikan Hormon progesteron untuk
memperkuat endometrium).
d. Tahap Gastrulasi
Tahap gastrulasi merupakan tahap pembentukan gastrula yaitu pembentukan tiga lapisan embrionik
pada embrio. Lapisan embrionik merupakan lapisan lembaga yang akan berkembang menjadi organ
– organ dalam embrio manusia. Gastrulasi ditandai dengan reorganisasi lapisan sel – sel pada tahap
blastula. Sel – sel blastula akan melakukan pergerakan morfogenetik yang sedemikian rupa, hingga
memungkinkan sel – sel yang berjauhan pada tahap blastula menjadi sel – sel yang berdekatan pada
tahap gastrulasi. Pergerakan sel – sel blastula pada tahap ini diawali dengan gerakan invaginasi atau
pelekukan ke dalam. Gerakan ini menyebabkan migrasi sel – sel yang awalnya terletak di luar
menjadi tersusun di bagian dalam. Pergerakan sel – sel ini menyebabkan rongga blastosol
menghilang, namun terbentuk rongga arkenteron.
Setelah semua sel berhasil bermigrasi, terbentuk lubang saluran bekas titik invaginasi yang disebut
dengan istilah blastopori. Selain gerakan invaginasi, sel- sel tahap blastula ini juga melakukan
gerakan evaginasi (melekuk keluar); ingersi (migrasi sel); dan lainnya. Selanjutnya, sel – sel ini
telah berhasil dan selesai dalam perjalanannya. Tahap gastrulasi ditandi dengan terbentuknya tiga
lapisan embrionik yang akan menentukan nasib embrio tersebut. Masing – masing sel dalam tiap
lapisan akan saling menginduksi satu sama lain untuk perkembangan selanjutnya. Tiap sel akan
menentukan takdirnya masing – masing. Oleh karena itu pada tahapan ini biasa disebut dengan
penentuan nasib (fate map). Tiga lapisan embrionik ini ialah antara lain lapisan ektoderm, lapisan
mesoderm, dan lapisan endoderm.
e. Tahap Neurulasi
Tahap neurulasi merupakan awal dari tahap diferensisi setelah tahap gastrulasi. Pada tahap
neurulasi merupakan tahap pembentukan corda saraf (notocord) yang merupakan ciri utama dari
hewan vertebrata. Notocorda dibentuk dari interaksi induksi antara lapisan ektoderm dengan lapisan
mesoderm di dalamnya. Induksi antar lapisan ini menyebabkan sel – sel ektoderm bergerak,
sehingga terbentuk notocorda yang memanjang. Untuk selanjutnya notocorda ini akan berkembang
menjadi sistem saraf pusat (perkembangan otak). Intinya tahapan neurulasi diindikasikan dengan
terbentuknya lempeng saraf (notocorda) pada lapisan ektoderm.
f. Tahap Organogenesis
Tahapan organogenesis merupakan tahapan pembentukan organ yang berkembang dari lapisan
embrionik yang terbentuk pada tahap gastrula.berikut organ – organ yang berkembang dari lapisan
embrionik:
1. Ektoderm yaitu lapisan yang paling luar. lapisan ektoderm akan berkemang menjadi sistem
integumen (kulit dan derivatnya), serta penyusun sistem saraf termasuk indera.
2. Mesoderm yaitu lapisan tengah yang akan berkembang menjadi organ dalam seperti sistem
sirkulasi, jaringan ikat, sistem reproduksi, otot, dan lainnya kecuali sistem pencernaan dan
pernapasan.
3. Endoderm yaitu lapisan paling dalam. Dari lapisan ini akan terbentuk organ – organ penyusun
sistem pencernaan meliputi saluran dan kelenjar pencernaan. Selain itu, sistem pernafasan juga
berkembang dari lapisan ini. Anus dan mulut berkembang dari asal yang sama yaitu pada blastopori.
2. Skeletal system formed during fetal life
Month 1: The Embryo Develops Three Layers
Soon after conception, the embryo differentiates into three layers of cells. The mesoderm, or
middle layer, will develop into your baby’s bones – as well as her muscles, kidneys and sex
organs. The inner layer (called the endoderm) becomes your baby's digestive system, liver and
lungs. And the ectoderm, or outer layer, develops into the nervous system, hair, skin and eyes.
Month 2: The Start Of Arms And Legs
Big changes are happening to your little embryo. It’s starting to develop a backbone, for starters,
while the neural tube forms – the source for parts of the nervous system as well as the spine and
skull. By about week 6, your little bean is also sprouting arms, hands, legs and feet. About the
only thing that isn’t growing is its tadpole-like tail; that’s shrinking and will eventually disappear
— leaving only the tailbone at the base of the spine.
Month 3: Fingers And Toes Appear
During these final weeks of your first trimester, your baby’s bones develop a lot. They start out as
little buds and grow into recognizable arms and legs, with joints, fingers and toes. Upper limbs
lead the way, with lower ones following — the same way motor skills develop after your baby is
born, from the top of the body down (lifting head, then pushing up, then crawling, then walking).
Month 4: Mom’s Supplying Baby Tons Of Calcium
Via the placenta, your body is now delivering calcium to your baby to help her bones harden,
strengthen and lengthen. This calcium transfer continues up until birth — she needs to absorb
about 30 grams of this important mineral from you over the course of nine months to build the
200+ bones that make up baby’s skeleton. So make sure you’re consuming plenty – about 1,000
milligrams (or 1 gram) of calcium a day helps your baby’s bones grow and safeguards your own
(your body won’t hesitate to deplete its own stores for your baby’s sake, so make sure to replenish
them regularly). Check the ingredients of your prenatal vitamin to see how much calcium it
includes, and make sure to chow down on foods rich in this important nutrient for bone
development (milk, soymilk, yogurt, cheese, canned salmon and edamame) along with plenty of
vitamin D (salmon, canned tuna, mushrooms and fortified cereal and orange juice) to help your
body absorb it. Also ask your doc whether you should take additional calcium supplements.
Months 5 And 6: Baby’s Moving Her Limbs
These are active months for bone-building. Your baby’s fingers and toes are well defined and he
can wiggle his limbs — you may begin to feel those flutters sometime around week 18. If you get
a peek at your baby during your week 20 ultrasound, you’ll now be able to see those bones he’s
busy building — they’re finally visible.
Months 7 And 8: Transforming Cartilage To Bone
How are you doing on that calcium consumption? Keep downing those dairy products, because
the majority of the calcium your baby gets from you is transferred during the third trimester –
about 250 milligrams a day! She’s busy transforming cartilage to bone as well as developing
muscle and building up a nice protective layer of fat.
Month 9: Baby’s Bones Remain Soft
At week 36, mother-baby calcium transfer peaks, with you passing along as many as 350
milligrams of the mineral every day. That’s the case even though your baby’s bones are still softer
than an adult’s. They have to be, so they can fit through the birth canal around week 40 and allow
room for growth once baby is born. Your baby’s skull, in particular, is designed for delivery: it’s
made up of several separate bony plates that can shift and compress as your baby’s head makes its
way toward the exit.
3. Fetal skeletal deformity
Classification
The existing nomenclature for skeletal dysplasias is complicated. Some disorders are referred to by
eponyms (such as Ellis–Van Creveld syndrome), by Greek terms describing a salient feature of the
disease (diastrophic or twisted, metatrophic or changeable) or by a term related to the presumed
pathogenesis of the disease (such as osteogenesis imperfecta). The fundamental problem with any
classification of skeletal dysplasias is that the pathogenesis of these diseases is largely unknown and,
therefore, the current system relies on purely descriptive findings of either clinical or radiological
nature. According to the International Nomenclature for Skeletal Dysplasias, the diseases are
subdivided into three different groups:
(1) Osteochondrodysplasias (abnormalities of cartilage and / or bone growth and development);
(2) Disorganized development of cartilaginous and fibrous components of the skeleton; and
(3) Idiopathic osteolyses.
4. The formation of long bone and membranous bone
Osifikasi tulang pipa
Osifikasi tulang spons
Jika matriks pada tulang berongga maka akan membentuk sebuah tulang spons, contohnya tulang
pipih. Sedangkan, apabila metriks tulang menjadi padat dan rapat, maka akan terbentuk tulang keras
atau tulang kompak, contohnya tulang pipa
5. Anatomy of upper and lower extremity
6. Bone physiology
The 206 named bones of the human skeleton are divided into two groups: axial and appendicular.
The axial skeleton forms the long axis of the body and includes the bones of the skull, vertebral
column, and rib cage. Generally speaking these bones protect, support, or carry other body parts.
The appendicular skeleton consists of the bones of the upper and lower limbs and the girdles
(shoulder bones and hip bones) that attach the limbs to the axial skeleton. Bones of the limbs help us
move from place to place (locomotion) and manipulate our environment.
Generally, bones are classified by their shape as long, short, flat, or irregular
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Long bones, as their name suggests, are considerably longer than they are wide. A long bone has a
shaft plus two ends which are often expanded. All limb bones except the patella (kneecap) and the
wrist and ankle bones are long bones. Notice that these bones are named for their elongated shape,
not their overall size. The three bones in each of your fingers are long bones, even though they are
small.
Short bones are roughly cube shaped. The bones of the wrist and ankle are examples. Sesamoid
bones are a special type of short bone that form in a tendon (for example, the patella). They vary in
size and number in different individuals. Some sesamoid bones act to alter the direction of pull of
a tendon. The function of others is not known.
Flat bones are thin, flattened, and usually a bit curved. The sternum (breastbone), scapulae
(shoulder blades), ribs, and most skull bones are flat bones.
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Irregular bones have complicated shapes that fit none of the preceding classes. Examples include
the vertebrae and the hip bones.
Functions of bones
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Support. Bones provide a framework that supports the body and cradles its soft organs. For
example, bones of the lower limbs act as pillars to support the trunk body when we stand, and the
rib cage supports the thoracic wall.
Protection. The fused bones of the skull protect the brain. The vertebrae surround the spinal cord,
and the rib cage helps protect the vital organs of the thorax.
Movement. Skeletal muscles, which attach to bones by tendons, use bones as levers to move the
body and its parts. As a result, we can walk, grasp objects, and breath. The design of joints
determines the types of movements possible.
Mineral and growth factor storage
Blood cell formation. Most blood cell formation, or hematopoiesis, occurs in the red marrow
cavities of certain bones.
Triglyceride (fat) storage. Fat, a source of energy for the body, is stored in bone cavities.
Hormone production. Bones produce osteocalcin, a hormone which not only helps regulate bone
formation, but also protects against obesity, glucose intolerance, and diabetes mellitus.