Embryology & Human Biology

REPRODUCTION & EMBRYONIC DEVELOPMENT OF AN ORGANISM

Organisms have the ability to reproduce by sexual or asexual means

I. Embryonic Development:

The basic body plan is established early in development

• Process of DEVELOPING a multicellular EMBRYO is quite complex and takes many steps

A. _FERTILIZATION : fusion of egg and sperm during sexual reproduction to produce a diploid zygote cell

B. _CLEAVAGE: repeated mitotic divisions of a zygote that makes a mass of cells• Takes several days• Cells have no function yet

C. _GASTRULATION: development of a multilayered embryo

• Cell Differentiation: embryo forms DIFFERENT tissue layers and cells SPECIALIZE to carry out a particular FUNCTION

• Cause:

a. Different GENES are ACTIVATED and signal cells to have different functions (example: liver, heart, blood cells, muscle cells)

b. The ENVIRONMENT can also influence differentiation

Ex: Metamorphosis Ex: Nutrition and Lifestyle

Metamorphosis

• _CHANGE in an animal’s APPEARANCE or structure from one stage to another through cell growth and differentiation

• May be influenced by change in HABITAT or behavior

Nutrition/Lifestyle:• Diabetes (type2): poor diet high in sugar leads to

insulin insensitivity

**body’s insulin tries to push the “gas pedal” but cells can’t react

II. THE HUMAN BODY• Later in embryonic development,

organs, made up of various tissue types, and organ systems work together to support the needs of the entire organism

• The body has been organized into 11 body systems that work together to maintain homeostasis and supports the major PROCESSES required for LIFE

_HOMEOSTASIS : steady internal state or condition

The body has FEEDBACK mechanisms that respond to changes in the organism's environment and will REVERSE the direction of the UNWANTED change

The body’s NERVOUS and ENDOCRINE systems along with other systems monitor body conditions inside and out

Changes in an organism’s homeostasis could be due to:

a. _DISEASE AGENTS such as bacteria 0r viruses

b. Changing PHYSICAL, CHEMICAL, or ENVIRONMENTAL conditions such as temperature, atmosphere, light exposure

III. EXAMPLES OF HOMEOSTASIS

• Cells function in a NARROW range of physical conditionsa. Temperature: body sweats to maintain normal

levelb. Blood pH: breathing controls CO2 levels in blood

c. Blood Sugar: insulin secreted from pancreas removes glucose from the blood

How is your homeostasis disrupted on a daily basis?

How does your body react to correct the situation?