human life cycle

**Spermatogenesis**

* Continuous process that begins in puberty and continues in old age
* Sperm production

**Oogenesis**

* Begins prior to birth which means within the embryo, 2 Primary Oogonium divide

1. 2 primary oocytes

Oogonium divides to form

**Gamete Formation**

* Eggs form and mature in female organs
* Sperm form and mature in male reproductive organs

**Fertilization**

* A sperm and an egg fuse at their plasma membrane
* The nucleus of one fuse with the nucleus of the other to form a zygote

**Cleavage**

Cell divisions carve up different regions of egg cytoplasm for daughter cells

**Gastrulation**

* Cell divisions, migrations, and rearrangements produce 2 or 3 primary tissues
* The start of specialized tissues and organs

**Organ Formulation**

Subpopulations of cells are sculpted into specialized organs and tissues in capital patterns at prescribed times

1. **Growth and Tissue Specialization**

Organs increase in size and gradually assume their specialized functions

**Cleavage**

* Series of cell divisions without growth or differentiation
* 4 days after fertilization

**Growth**

* Zygote receives nutrients and begins to grow in size
* Every time the cell divides, 2 daughter cells double in mass

**Differentiation**

* Cells take specialized forms and functions that lead to different types of tissues
* 16 cells

**Morphogenesis**

Cells change in shape starting as a ball of identical cells to germ layers

**Morula**

* Sixteen-celled zygote
* Mulberry
* uterus

**Blastomere**

Each new cell that forms during cleavage

**Gastrulation**

* Process of early development that produces the 3 germ layers
* Germ layers (3 primary tissues that form as an early embryo develops)

**Cell Differentiation**

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Newly formed cells become specialized for a certain function

**Morphogenesis**

* The beginning of form
* Specific organs and tissues form

**Ectoderm**

* Nervous system
* Sense organs
* Pituitary gland
* Epidermis and associated structures (hair)

**Mesoderm**

* Cartilage
* Bones
* Muscles
* Lymphatic system
* Cardiovascular system
* Urinary system
* Reproductive 
* Outer layers of digestive system

**Endoderm**

* Lining of the digestive tube
* Lining of the respiratory airways

**Blastocyst**

* Embryonic stage that develops from morula and will eventually implant the uterine wall
* Secretes human chorionic gonadotropin (HCG)
* Happens when the morula enters the uterus

**Tropoblast**

Surface epithelium

**Inner Cell Mast**

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Small clump of the cell where the embryo develops

**Ectopic pregnancy**

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Implantation occurs somewhere other than within the uterus, such as in one of the uterine tubes