by 124L - animal dev. & muscle physiology

What structures are the arrows pointing to?

explain the state of an unfertilized egg in terms of the fertilization stage (according to this model)

• the egg nucleus is yet to finish meiosis

• no fertilization —> egg is flushed out with monthly cycle

explain the state of a fertilized egg in terms of the fertilization stage (according to this model)

• finishes meiosis II, the egg is at metaphase II

• polar body (unstable cell) is kicked off

• egg nucleus fuses with sperm nucleus

explain the state of an embryo in terms of the first cleavage process (according to this model). be able to identify the dark hemisphere, the animal pole, the light pole (vegetal pole) on this model

• divides single diploid cell into lots of smaller cells

• no change in size

• the first cleavage is polar/vertical

explain the state of an embryo in terms of the second cleavage process (according to this model).

• second division/cleavage is along the polar/vertical axis

• at the end of this process, there are 4 cells in the embryo

what is each cell that is produced from cleavage called?

blastomere

explain the state of the embryo in terms of the third cleavage process (according to this model).

• third cleavage is along the horizontal/equatorial axis

• this yields an embryo of 8 cells/blastomeres

explain the state of the embryo in terms of the fourth cleavage process (according to this model).

• embryo has 16 cells total

• cleavage will continue until a solid ball of cells (morula) is produced

explain the state of the new morula in terms of the blastulation process (according to this model).

• characterized by a fluid-filled space forming (blastocoel)

what structure is the arrow pointing to in this model?

blastocoel

what is occurring in this model?

the process of forming a blastocoel still continues

what structure is the arrow pointing to?

dorsal lip of blastopore

explain the state of the embryo in terms of the blastula process (according to this model).

• embryo is now called the blastula

• the ectoderm is now formed as the upper layer that’s shaded blue

what is the importance of the blastopore?

this is where cells invaginate inward during the process of gastrulation (where three primary germ layers are laid down)

explain the state of the blastula in terms of the gastrulation process (according to this model).

• cells are now migrating inward

• the blastocoel is being obliterated, a new cavity (archenteron) is developing in its place

what structures are the arrows pointing to?

explain the state of the blastula in terms of the last stage of the gastrulation process (according to this model).

• all three germ layers are formed

• ectoderm, mesoderm, endoderm are present (blue, pink, yellow)

• this is the first time the cells become differentiated

what structures are the arrows pointing to?

explain the state of the blastula in terms of the neurulation/organogensis process (according to this model)

• formation of the nervous system (neurulation) and organs (organogensis)

  • first 2 organs to form: neural tube from ectoderm & notochord from mesoderm

explain the state of the blastula in terms of the neurulation/organogensis process (according to this model)

• neural tube continues to form at the top of the model

• archenteron begins to take a dif. shape on as it forms the gut

• the vegetal pole cell area reduces in size as it’s used up to fuel the active cell division above it

explain the state of the blastula in terms of the neurulation/organogensis process (according to this model)

• top of the model is where the ectodermal cells have sunk in and formed a ditch

  • ditch covered over itself and begun to sink downward into the embryo

explain the state of the blastula in terms of the neurulation/organogensis process (according to this model)

• the ectodermal ditch continues to sink into the embryo

• archenteron region’s ends have migrated to each end of the embryo

  • when it reaches the left end of the model that’s where the mouth will be

• right side of the embryo: blastopore opening —> anus

what structures are the arrows pointing to?

explain the state of the blastula in terms of the neurulation/organogensis process (according to this model)

• the sunk end ectodermal cells are now lighter blue —> neural tube

  • blue - from ectoderm, light blue - ectoderm is specialized

• the left end of the model becomes the brain

  • tapering area that leads from this will become the spinal cord

what structures are these arrows pointing to?

explain the state of the blastula in terms of the neurulation/organogensis process (according to this model)

• neural tube (light blue) continues on its development to produce the brain and spinal cord

• the notochord (grayish-purple) provides a “support beam” for cell attachment and also gives cues to where cells need to migrate in order to produce required structures

• endoderm now stretches from mouth to anus ends of embryo

explain the state of the blastula in terms of the neurulation/organogensis process (according to this model)

• one celled zygote transformed into a shape that looks closer like the frog’s tadpole stage

• blood vessels are now visible

• reddish regions are beginning to produce muscle

define differentiation

the process by which unspecialized cells become specialized cells that are ordered in the tissues and organs of the animal

define morphogenesis

the development of the animal’s shape, or body form, and organization.

what does embryonic development begin with?

fertilization

define fertilization

the union of two haploid gametes to form a diploid zygote (a fertilized egg)

what are the two functions of fertilization?

1. to combine 2 haploid sets of chromosomes, contained in the gametes of 2 different individuals, into a single diploid set (1n + 1n = 2n)

2. to activate the egg

   a. binding of the sperm with the egg causes a chain of metabolic reactions within the egg that triggers the onset of development

explain how the meiosis stages change for an egg in a female depending on the timeline of her life

• at birth, born w all eggs they will ever have (prophase I)

• each menstrual cycle, eggs progress to metaphase II and stop

  • if unfertilized: it will be lost w menstrual flow

what follows fertilization?

cleavage

define cleavage & summarize the process.

a rapid succession of cell divisions that produce a solid ball of cells from the zygote

• the embryo doesn’t grow in size during this time

• cytoplasm of one large cell is partitioned off into many smaller cells (blastomeres)

list the different axes that correspond with the different cleavages

first and second - vertical/polar

third - horizontal/equatorial

what is produced as cell division continues?

morula (solid ball of cells)

what forms in the center of the morula?

a fluid-filled cavity called a blastocoel

what stage does the developing embryo enter after the blastocoel is formed?

blastula stage (hollow ball of cells)

what follows cleavage?

gastrulation

summarize the gastrulation process.

cells from the outer surface of the embryo begin to migrate inward toward the center

• specifically move through the blastopore (mouth in protosomes, anus in deuterostomes)

blastocoel is obliterated and the new archenteron cavity is formed, which becomes the digestive tract when fully developed.

3 primary germ layers develop

developing embryo from blastula —> gastrula

what are the 3 germ layers?

• ectoderm (outer layer)

• mesoderm (middle layer)

• endoderm (inner layer)

what structures does the ectoderm produce?

• nervous system

• epidermis & associated glands of the skin (sweat and sebaceous)

• inner ear

• lens of the eyes

• adrenal medulla

what structures does the mesoderm produce?

• notochord

• lining of the coelom (body cavity)

• muscles

• skeleton

• gonads

• kidneys

• most of circulatory system

• lymphatic system

• dermis of skin

• adrenal cortex

what structures does the endoderm produce?

• lining of the digestive tract

• organs that originate as out-pockets of the archenteron (ex: liver, pancreas, gall bladder)

• thyroid

• parathyroid

• lungs

• thymus

• urinary bladder

what comes after gastrulation?

neurulation

summarize the process of neurulation.

• outer, ectodermal cells flatten out and sink downward to form a groove called the neural groove

• edges of either side of the groove eventually become elevated —> neural folds

• folds come toward each other, eventually touching, then fusing to form a hollow neural tube

what comes after neurulation?

organogenesis (the formation of organs)

summarize the process of organogensis.

first organs take shape: neural tube (from dorsal ectoderm) and notochord (from dorsal mesoderm)

• neural tube —> brain and spinal cord

• notochord —> intervertebral discs between the vertebrae

blocks of mesoderm begin to condense, forming blocks of somites —> vertebrae of backbone

label this picture with the corresponding structures.

what is the function of the following extra-embryonic membrane of the amniotic egg: chorion

Develop the villi and the placenta that will provide a pathway for exchange from the mother to the fetus, making it a pivotal part of the development

what is the function of the following extra-embryonic membrane of the amniotic egg: amnion

A transparent sac filled with colorless fluid that serves as a protective cushion during embryonic development

what is the function of the following extra-embryonic membrane of the amniotic egg: yolk sac

Serves as an absorptive epithelium for nutrient uptake and secretion as well as the origin of the first blood cells

what is the function of the following extra-embryonic membrane of the amniotic egg: allantois

Serves as a temporary respiratory organ while its cavity stores fetal excretions

how is a frog egg particularly different?

they’re polar in the sense that there are 2 distinct hemispheres:

• one hemisphere actively divides to form the animal (animal pole)

• second hemisphere doesn’t divide but rather provides the energy for the actively dividing cells in the animal pole (vegetal pole)

  • acts as the yolk

summarize the process of fertilization and cleavage

two haploid gametes form a diploid zygote

cleavage follows right afterwards, rapidly dividing cells to produce solid balls of cells from the zygote

• a morula is produced from here —> blastocoel —> blastula

what are the three basic muscle types?

cardiac, smooth, skeletal

skeletal muscle is usually attached to what?

bone

what do skeletal muscles move?

skeleton

the ____ nervous system controls skeletal muscles

somatic

are skeletal muscles voluntarily or involuntarily controlled?

voluntarily

where do you usually find smooth muscle?

hollow organs & tubes

• stomach

• intestines

• bladder

• blood vessels

smooth muscle is controlled by the _____ nervous system

autonomic

smooth muscle control is largely what?

hormones

where is cardiac muscle found?

heart muscle

what two factors does it respond to?

ANS and hormones

skeletal muscle contains many muscle cells called ______ which are bound by what?

muscle fibers; connective tissue

a single muscle cell contains many _____ which extend the length of the cell

myofibrils

muscle cells contract along their _______

length

striations are seen in which two types of muscle?

cardiac and skeletal

myofibrils contract _______ which in turn, contract __________

myofibrils; muscle fibers

myofibrils exhibit alternate dark and light bands along their what? this results in a similar banding pattern seen in the muscle cell itself.

length

skeletal muscle is often called what?

striated muscle

which 2 of the 3 muscle types are striated?

cardiac and skeletal

in a myofibril, the dark bands are called ________

a bands

in a myofibril, the light bands are called _____

i bands

in the middle of the I bands are other bands called _________

z bands

the a bands have light areas bisected by bands called ______

m lines

the functional unit of the myofibril is called a(n) _______

sacromere

a sacromere extends from what to what?

z line to another z line

contraction of myofibrils is caused by the contraction of each _______

sacromere

a sacromere is comprised of two proteins called what?

actin and myosin

a thin filament consists mostly of 2 molecules of ________

actin

a thick filament is comprised of hundreds of ________ molecules

myosin

thin filaments are connected at one end to the ______, a structure that runs across the myofibril

z line

the thick filaments are connected to the _____, a structure that runs across the myofibril

m line

the dark areas of the a band correspond to regions where what two structures overlap?

thick and thin filaments

the light area in the middle of the a band (called the _______) consists of thick filaments only

h zone

the width of the a band corresponds to what?

length of thick filaments

the _______ correspond to regions consisting of thin filaments only.

i band

both types of filaments are anchored, thin to _____ and thick to ______

z line; m line

the z and m lines run through the myofibrils and thus align what?

sacromeres

the width of the ___ band remain constant throughout contraction

A

contraction does narrow the ___ bands and the ___ zone as the ___ lines come closer together. also, the dark areas of the ____ band become wider

contraction does narrow the I bands and the H zone as the Z lines come closer together. also, the dark areas of the A band become wider

the width of the A band equals the length of the _____ filaments

thick

since the width of the A band remains constant, the ____ filaments do not shorten during contraction

thick

do the thin filaments shorten during contraction?

no

sacromeres contracts the muscle cell which leads to the contraction of what?

myofibrils and then the muscle itself

muscle cells contract because the ____ are connected to the cell membranes

z lines

a myosin molecule consists of 6 polypeptide chains. how many are light? how many are heavy?

2 heavy

4 light