prenatal animal growth & development · fetal fact: the fetus is about the size of a grey...

Prenatal Animal Growth & Development - Student Notes

Accompanies: Prenatal Animal Growth & Development 1

Directions: Fill in the blanks. Embryonic & Fetal Development Segment 1. Embryonic & Fetal Periods • Embryonic period

– period from _______________ to the earliest stages of organ development

– about 30 days in sheep, goats and pigs – about 60 days in horses and cattle

• Fetal period – time between _______________ period and birth – time in which organs grow and begin to function

2. Embryonic Development • Is the process in which a zygote is transformed into an

_______________ organism • Includes the following stages:

– fertilization – _______________ – gastrulation – organogenesis – growth

3. Embryonic Development Stages



4. Fertilization • Begins with the fusion of two _______________

– initiates the process of development • Ends with the initiation of _______________ cell division

– cell formed when two gametes join – earliest stages of the embryo

5. Cleavage • Is the division in which the number of cells making up a developing

_______________ increases – size of embryo stays the same

• Ends with the formation of a _______________ – hollow sphere of cells – when grouped together, are called “blastomeres”

6. Gastrulation • Is when cells begin to assume different and _______________ forms

and functions • Is the process which gives rise to three germ layers

– _______________ – mesoderm – endoderm

Fetal Fact: Each layer arises simultaneously and plays a special role in completing the animal. 7. Gastrulation



8. Ectoderm • Forms _______________ of skin, nervous system and

_______________ system

9. Mesoderm • Forms _______________, bone, circulatory system, urinary and

_______________ systems

10. Endoderm • Forms _______________ of the respiratory and _______________

systems



11. Organogenesis • Is the last major step of embryonic development • Occurs when various regions of the three germ layers develop into the

_______________ of organs – involves cell movement and cell _______________

12. Growth • Is when the organism increases in size

– happens _______________ gestation – happens simultaneously with gastrulation and _______________ – process of development in the womb

13. Gestation

Cattle Gestation Period Segment 1. Month One (Cattle) • From fertilization to 30 days • Embryo is 9 to 10 _______________ or 0.4 inches • Shows signs of extremities consisting of joints and legs • Heartbeat is established • Development of organs such as:

– liver – _______________ – lungs – brain – kidneys



2. Month Two • From day 30 to 60 • Fetus continues to grow

– from 1 to 3 inches in length • Shows development of _______________ • First indication of the hooves • _______________ system begins to develop Fetal Fact: Fetus is now the size of a mouse. 3. Month Three • From day 60 to 90 • Fetus is approximately 5.5 inches in length • Four stomachs may be recognized • _______________ development in males • _______________ development in females 4. Month Four • From day 90 to 120 • Fetus is approximately 9.5 inches in length • Fetus weighs up to _______________ • _______________ become distinct Fetal Fact: The fetus is about the size of a grey squirrel. 5. Month Five • From day _______________ • Fetus continues to grow

– up to 14 inches in length – weighing approximately 2.5 to 3 kilograms

• First _______________ appear on lips, chin and upper eyelid • Teats are plainly visible • Testicles descend into scrotum 6. Month Six • From day _______________ • Fetus is 18 inches long • _______________ are developed • Whole body is hairless

– except for lips, chin and eyelids



7. Month Seven • From day 180 to 210 • Fetus is approximately 23.5 inches in length • Hair appears on the _______________ • Hair covers the spots where the _______________ will appear Fetal Fact: 23.5 inches is approximately the length of two rulers. 8. Month Eight • From day 210 to 240 • Fetus continues to _______________ anywhere from 25 to 30 inches

in length • Hair covers the back and edges of _______________ 9. Month Nine • From day 240 to 270 • Fetus measures anywhere from 30 to 40 inches in length • _______________ body is covered in hair • Body increases greatly in size • Final development of _______________ 10. Month Ten • From day 270 to birth • Fetus become _______________ • _______________ Horse Gestation Period Segment 1. Month One (Horse) • From fertilization to 30 days • Embryo starts to grow

– starting out as no bigger than a _______________ – 0.25 up to 1 inch in diameter

• Beginning _______________ become apparent – including head, tail nub, four buds which will become the legs and

bumps which will become eyes



2. Month Two • From day 30 to 60 • Embryo becomes a _______________

– 2.25 to 3 inches in diameter – 0.75 up to 1 inch in length

• Features become distinct – including legs, eyelids, tiny ribs, skull, ears, hock and fetlock joints

• Functional joints including elbows and stifle joints • Apparent _______________ 3. Month Three • From day 60 to 90 • Fetus becomes more horse-like

– approximately 2.5 inches in length – untucking of the head by the end of the month

• _______________ may be determined • Development of tiny _______________ Fetal Fact: The fetus will grow to the size of a chipmunk.

4. Month Four • From day _______________ • Fetus continues to grow up to 7 inches in length • Hair appears on lips • _______________ are unfurling from head • 0.25 inch hooves

5. Month Five • From day 120 to 150 • Fetus continues to grow up to _______________ • Hair appears on chin, _______________ and eyelids • Eyelashes develop Fetal Fact: The fetus is now the size of a rabbit. 6. Month Six • From day 150 to 180 • Fetus continues to develop • _______________ and tail _______________ appear



7. Month Seven • From day 180 to 210 • Fetus continues to grow

– weighs nearly _______________ • quadrupling in weight

• Eyelids capable of _______________ 8. Month Eight • From day _______________ • Fetus continues to develop • Whisker-like _______________ on chin, throat and muzzle Fetal Fact: The fetus is now the size of a small lamb. 9. Month Nine • From day 240 to 270 • Foal begins to gain weight

– gains as much as a _______________ a day • _______________ continue to develop 10. Month Ten • 270 to 310 days after fertilization • Growth continues • Fine hairs cover the entire body • _______________ now looks like a foal • Final stages of _______________ development Fetal Fact: Fetus is now the size of a German Shepard.

11. Month Eleven • From day 310 to birth • Fetus becomes mature • _______________ • Legs strengthen • Hair has _______________ • Birth



Swine Gestation Period Segment 1. Month One (Swine) • From fertilization to 30 days • Embryo growth begins in uterine

– grows up to 0.6 inches • _______________ becomes recognizable • Organs begin to differentiate • By day 22 the skeletal muscles can be seen • Ovaries and testes are _______________ and are secreting sexual

hormones • Major organs are visible 2. Month Two • From day 30 to 60 • _______________ become a fetus, growing up to approximately 1.5

inches in length • _______________ begins to form 3. Month Three • From day 60 to 90 • Fetus is _______________ 8 inches in length • The lungs and brain continue to grow • Becoming more pig-like

– growth of skin, hair and hooves • Final stages of lung _______________ Fetal Fact: Eight inches is the width of a piece of paper.

4. Month Four • From day 90 to birth • _______________ grows to approximately _______________ in

length • Birth



Sheep & Goat Gestation Period Segment 1. Month One (Sheep and Goat) • From fertilization to 30 days • Embryo is 0.5 inch long • Lungs begin to form • _______________ buds appear • Apparent _______________ 2. Month Two • From day 30 to 60

– embryo becomes a fetus – growing up to 1.5 inches in length

• Differentiation occurs in mouth, extremities and dew claws • _______________ and eyes become apparent • Sex can be determined • _______________ divisions differentiated • Major tissue, organ and systems are defined Fetal Fact: The fetus is about as long as a large paper clip. 3. Month Three • From day 60 to 90 • Fetus grows up to 4 inches in length • _______________ open • Hairs appear on the eyelids and muzzle • _______________ appear 4. Month Four • From day 90 to 120 • Fetus is 10 inches in length • Hair appears • Pigmentation begins around horn pits • Skin is thicker and _______________ • Respiratory system is established • Top of head hardens • _______________ Fetal Fact: Ten inches is the height of a 20 oz. coke bottle.



5. Month Five • From day 120 to birth • Fetus is able to _______________ on its own • Fetus _______________ • Birth Poultry Gestation Period Segment 1. Week One (Poultry) • From day 1 to day 7

– grows more than1 inch and up to 1/2 a gram • Development of nervous system, reproductive organs and brain • _______________ system well developed • Formation of appendages

– rapid _______________ development • Heart begins to beat 2. Week Two • From day 8 to day 14

– grows from 1 gram up to 10 grams • Becomes more chick-like • Wings, feet and toes are well developed • Appearance of _______________ • Beak begins to harden • _______________ and claws appear Fetal Fact: A quarter weighs approximately 5.5 grams 3. Week Three • From day 15 to day 21

– embryo will grow up to 30 grams • Embryo grows rapidly occupying all the _______________ within the

egg • Chick assumes hatching _______________ and breaks through the

shell • Birth



Postnatal Development Segment 1. Postnatal • Refers to the period after birth • Organs are all present and developed

– organs will go through maturation • Bones are complete

– bones will grow in length through _______________ • process of laying down new bone material by cells

– after hardening, bones will stop growing but bone tissue is continually being _______________

2. Postnatal • Muscle fibers are present

– no new fibers are formed after birth – fibers will grow in length and _______________ with the growth

of the animal • Fat tissue is present but in small amounts

– most fat comes after birth – cells will increase in size throughout growth – depends greatly on the _______________ status of the animal

prenatal animal growth & development · fetal fact: the fetus is about the size of a grey...

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