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Pertumbuhan dan Perkembangan Manusia

Perkembangan Embrio dalam Rahim

• Sebelum menempel pada dinding rahim zygot tumbuh dan berkembang dengan membelah terus melalui stadium morula blastula dengan blastocoelnya , pembelahan ini terjadi sejak terjadi fertilisasi di tuba falopii dan bergerak ke endometrium uterus , setelah menempel di uterus tumbuh terus ke fase gastrula kemudian berdefrensiasi dan specialisasi membentuk embryo

• Embrio yang menempel pada rahim (uterus) terus tumbuh dan berkembang sampai terbentuk dua bagian
• Bagian pertama berupa embrio yang akan menjadi janin, bagian lain akan membentuk membran ekstraembrio.
• Membran ekstraembrio ini selanjutnya membentuk amnion dan tali pusat yang merupakan penghubung antara embrio dengan jaringan induknya.
• Fungsi plasenta dan tali pusat adalah untuk mengalirkan makanan dan oksigen dari induk ke embrio serta mengalirkan sisa-sisa metabolisme embrio ke peredaran darah induknya.

Perkembangan embrio selanjutnya adalah sebagai berikut.

1. pada umur empat minggu, janin sudah memperlihatkan pertumbuhan mata dan telinga;
2. pada umur kira-kira 8 minggu, janin sudah mirip dengan bayi dengan kepala lebih besar, mata, telinga, hidung, jari tangan dan jari kaki mulai terlihat;
3. pada umur 10 minggu, panjang embrio kira-kira 6 cm, ukuran kepala masih lebih besar dari badannya;
4. pada umur kira-kira 8 bulan (32 minggu), panjang janin kurang lebih 40 cm;
5. pada umur kira-kira 9 bulan, bayi mencapai perkembangan yang sempurna dan panjangnya kira-kira 50 cm serta beratnya + 3 kg. Begitu bayi siap untuk dilahirkan otot-otot pada rahim berkontraksi secara teratur dan mendorong bayi keluar dari rahim melalui vagina.

2. Tahapan Perkembangan Manusia

• Pada masa pubertas, terjadi pertumbuhan sekunder dan pematangan organ kelamin manusia sehingga mampu bereproduksi atau manghasilkan keturunan. Pertumbuhan sekunder yang terjadi pada anak laki-laki dan wanita selama masa pubertas dapat dilihat sebagai berikut.

Catatan tambahan :

• Pertumbuhan adalah proses perubahan progresif yang bersifat kuantitatif dan yang terjadi pada aspek fisik.
• Contoh pertumbuhan : munculnya gigi-gigi baru, bertambahnya tinggi badan, bertambahnya panjang rambut, dst.

• Perkembangan adalah proses perubahan progresif yang bersifat kualitatif fungsional dan yang terjadi pada aspek fisik dan psikis.
• Contoh perkembangan : munculnya kemampuan berdiri dan berjalan, semakin meniningkatnya kemampuan berbicara, berimajinasi, berpikir, berbicara, dll.

Growth and Development Stages in Human

The growth of humans starts from fertilization to the old age. Generally, human life can be divided into several stages as follows :

1. Prenatal Stage

• Prenatal development is the process in which a human embyro or fetus gestates during pregnancy, from fertilization until birth.
• After fertilization the embryogenesis starts. In humans, when embyrogenesis finishes, by the end of the 10th week of gestational age, the precursors of all the major organs of the body have been created.

• Fertilization : the fusion of sperm nucleus with ovum nucleus producing fertilized ovum (zyogte).
• About 36 hours after fertilization,the fertilized ovum divides once into 2 cells.
• After 72 hours from fertilization, the zygote divides into 16 cells which will stick on the uterus in several days later.
• After 4 weeks, the embryo floats in a sack containing liquid;the heart beats and the brain has developed.
• After 5 weeks, the embryo is as big an apple seed with hand and foot primordia, and the tail reduces.
• After 12 weeks, the embryo is called fetus which is in the size of strawberry, the hands and feet have developed.
• After 28 weeks, the fetus develops and it’s weight increasses until the delivery time.
• After 38 weeks, the fetus turns its head to the lower part of the womb, preparing for its birth.

• A fetus is an embryo which has complete organ system.
• In the mother’s womb, the fetus is inside a membrane containing liquid called amnion .
• It protects the fetus from shocks, cold, and heat.

2. Toddler and Childhood Stages

• The important development happens in the neonatal stage (0-30 days), at the age of 0-2 years old and of 2-6 years old.
• Toddling stage is the peak of human brain growth. At the age of 1-2 years old, the human brain growth decreases; at that period, however, the movement develops.
• At the age 2-6 years old, the physical growth slows, but the physical activity increases.

At the age of 1-3 months old, a baby is able to face downward

• Active hand movement when facing downwards, raising its head, holding reflex, sucking, swallowing and noticing voice ( At the age of 1-2 months old )
• Sucking fingers, rocking toys, the eyes following the movement of things and people around, staring at things, and smiling ( At the age of 3 months old )

At the age of 5-8 months old, a baby is able to sit up unaided.

• Raising its head, sitting up assisted turning its body,reaching things. Eyes following toys movements. There is coordination between hands and eyes. In this age, children’re more active ( At the age of 5-6 months old )
• A baby is able to sit up unaided and the previous abilities improve, able to eat biscuits unaided, hold spoon assisted, hold toys in one hand.( At the age of 7-8 months old )

At the age of 9-24 months old

• Using fingers for chooseing things, starting to crawl and standing up assisted. ( At the age of 9-10 months old )
• Walking assisted,drinking with glass.( At the age of 11-12months old )
• Walking ability improving, moving back and forth, spinning and starting to run.( At the age of 18 months old )
• Running, stepping up to stairs, actively playing. ( At the age of 24 months old )

In the early age of 6-12 years old, baby teeth start to fall and are replaced by permanent ones. Children have strong memory.

3. Adolescence (10-20 years)

• At the age of 12-20 years old, a person is in adolescence stage.
• Adolescence stage is the transition period from childhood to adulthood.
• At this time a person experience unique and interesting psychological and physical changes called puberty.
• In male adolescence, the acceleration occurs at the ages between 12-20 years old.
• While the female adolescence, the growth acceleration happens at the ages between 10-18 years old.
• Puberty is a period of reproductive organ maturation.
• It becomes the starting point of the adolescence period, indicated by endocrine system activation.
• The endocrine system is a gland system producing hormones regulating body’s activities, growth, and reproductive organ maturation.

Changes in a Female Adolescence

• What changes are experienced by a female adolescent during her puberty?
• The process starts after the pituitary gland releases hormone which activates ovaries.

The development of reproductive organs will be followed by the development of secondary sexual characteristic as follows :

1. The development of breast and the growth of hairs around the genital and armpits.
2. The increase of hip width.
3. The change of voice.
4. The increase of skin pore width and skin oil production, which causes pimples.

What is the most important thing happening during puberty in female adolescent?

• Other important development is the development of reproductive organs to reach its maturity.
• This is marked by menstruation, that is the releasing of blood from the womb due the unfertilized eggs.
• The bleeding occurs because the release of eggs is accompanied by the drop of the womb wall which is prepared for fetus development.
• Normal menstruation occurs regulary every month or once in 28 days, ± 7 days.
• Generally, it lasts for 3-8 days.
• Usually, the first menstruation happens when girls its about 12-16 years old.

Change in a Male Adolescent

• Usually, a man achieves his adult size at the age of 20 years old.
• The maturity of sexual organs in a male adolescent is influenced by the activity of hypothalamus which triggers the activity of the sexual glands (testicles).

Puberty in male adolescent is mark by wet dream and the develompent of the secondary sexual characteristic as follows :

1. The growth of hari around the genital, armpits, arms, legs, and chest.
2. The increase in vocal chord length, so the voice becomes deeper and heavier.
3. The increase of shoulders and chest width.
4. The increase of the production of skin oil which causes acne problems.

4. Adulthood and Old Age Stage

• The peak of human growth is in the adulthood stage.
• In this step, body, reproductive organ psychological developments are in the peak of their activity.

What symptoms occur when we get older?

• The regression can be physical or mental.
• Moreover, the body vitality also reduces and undergoes some health problems.
• Senescene can’t be avoided, but it can be delayed.
• In order to delay the senescene, appropriate heatlh care, regular exercise, and health food intake are needed.

SOAL LATIHAN

1. Mahkluk hidup setiap hari bertambah banyak karena ….

A. hidup dan tumbuh

B. peka terhadap rangsangan

C. berkembang biak

D. tumbuh dan bergerak

2. Tahapan makhluk hidup menuju kedewasaan dimulai pada masa....

A. pubertas

B. zygot

C. janin

D. embrio

3. Berikut perubahan fisik pada laki-laki, kecuali....

A. suara membesar

B. panggul membesar

C. tumbuh kumis

D. tumbuh jakun

4. Masa pubertas adalah masa ....

A. pertumbuhan paling cepat

B. pertumbuhan di atas 12 tahun

C. kematangan maksimal fisik

D. kematangan organ reproduksi

5. Masa puber laki-laki … dari pada perempuan.

A. lebih cepat

B. lebih lambat

C. beriringan

D. bersamaan

6. Ciri yang menandai masa pubertas pada anak laki-laki adalah ....

A. dada menjadi bidang

B. payudara mulai tumbuh

C. pinggul membesar

D. mengalami menstruasi

7. Perubahan primer perempuan pada masa puber adalah ....

A. suara makin nyaring

B. payudara membesar

C. mimpi basah

D. mulai menstruasi

8. Pada saat manusia memasuki usia lanjut, perubahan yang terjadi adalah ....

A. mulai berkembangnya organ reproduksi

B. mulai terjadi perubahan fisik secara sekunder

C. mulai memproduksi sel kelamin

D. mulai terjadi penurunan fungsi tubuh

9. Bayi manusia berada dalam kandungan selama kurang lebih ....

A. 21 bulan

B. 10 bulan 9 hari

C. 9 bulan 10 hari

D. 6 bulan 15 hari

10. Pertumbuhan fisik yang pesat pada masa puber dipengaruhi oleh ....

A. hormon kelamin

B. zat makanan

C. jenis kelamin

D. bentuk fisik