Diagrams

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Zygote

A one-celled organism formed by the union of a sperm and an egg.

4 basic cell functions

multiply, move, signal, differentiate

Spermatogenesis

Formation of sperm

Oogenesis

formation of egg, each division produces a polar body so that there is lots of cytoplasm in the oocyte so it can survive

fertilization

12-24 hours after ovulation

First stages of life order

1. fertilization 2) one cell stage (zygote) 3) first cleavage

first week

cells undergo cleavage using energy from cytoplasm (costly) to create blastocyst

blastocyst

has cell differentiation

Embryoblast

inner cell of blastocyst (future embryo)

trophoblast

outer layer of blastocyst (supportive structure)

second week

blastocyst gains access to uterine wall (blood) and embryoblast divides in to two

epiblast

top layer of embryoblast division (future embryo)

hypoblast

bottom layer of embryoblast division (yolk sack)

Gastrulation

begins with a primitive then three germ layers: ectoderm, mesoderm, endoderm

ectoderm

originally the epiblast/ will form head, nervous system, epidermis

primitive streak

an invagination that develops along midline on dorsal side starting from caudal end formed from inward migration and rapidly dividing and differentiating epiblast cells (first hypoblast cells are replaced and epiblast cells form endoderm then they form mesoderm)

mesoderm

mid section formed by migrating epiblast cells/ skeletal, muscle, lymph, reproductive systems

endoderm

formed from epiblast cells that replace hypoblast/ digestive, respiratory, most of endocrine

notochord

hardened rod down central axis formed from mesoderm

third week

embryo has three layers

Neuralation

the process of forming the neural tube which will become the CNS

neural folds

ends of stiffened ectoderm that rise and cause neural groove

neural groove

depression caused by neural folds

neural tube

made from ectoderm, will become CNS

somites

segmented swells of mesoderm along the notochord.. will form repetitive structures such as vertebrae

lateral mesoderm parts

splanchnic (lower) and somatic (higher)

visceral peritoneum

formed from the splanchnic mesoderm and lines the external surface of organs

parietal peritoneum

formed from the somatic mesoderm and lines the internal body wall

mesentries

formed by connection of left and right splanchnic mesoderm/ double layered/ used to tether organs to body

coelome

big empty space between gut tube/splanchnic mesoderm and somatic mesoderm which will develop in to the abdominal cavity

neural plate

folds to create neural tube.

Blind Watchmaker Analogy

evolution by natural selection is agentless (blind) so how could something so complex have no "guide"

solutions to blind watchmaker problem

1. many steps to make changes 2. the process of development promotes and permits evolution because there is lots of integration between many modules

evolutionary change

descent with modification (development is hierarchical)

Somite differentiation

sclerotome and dermomyotome

sclerotome

gives rise to the vertebrae

Dermomyotome differentiation

dermatome and myotome

Afferent neurons

neural crest cells sent out on dorsal side (sensory receptors to CNS)

efferent neurons

neural crest cells sent out on ventral side (CNS to motor receptors)

myotome cells

mesoderm cells that form muscle and migrate and bring neurons with them

epaxial

myotome nerve cells on dorsal side

hypaxial

myotome nerve cells on ventral side

Vertebra formation

each vertebra is half of one segment plus half of another so that spinal nerves emerge between vertebrae and muscles cross over.

Primitive Fins

specialized flaps of the body wall (lateral plate mesoderm). Muscle splits on either side in to elevators and depressors

bud

beginning of a limb in lateral plate mesoderm. position is determined by somite signaling

apical ectodermal ridge

organization center on the most lateral part of the bud that sends out signals causing cell differentation

Head key facts

1. heads like limbs are evolutionary novelties 2. many distinct modules become highly integrated 3. lots of opportunity for integration

neural tube segments

forebrain, midbrain, hindbrain, spinal cord

neural crest cells

migratory, pluripotent (can differentiate into many types), go over head like hoodie and form face or become branchial arches

Branchial Arches

streams of neural crest cells that go over sides like collar and form gills or neck. They have a nerve, blood vessel, ectoderm, endoderm, and mesoderm.

cleft

neural crest cells fail to fuse at midline

functional roles of the skeleton

1. stiffness 2) strength 3)mineral (Ca++) homeostasis, 4) make blood 5) permit movement around joint

purpose of skeleton

oppose gravity, allow muscles to generate movement, protect organs

strength

maximum force before failure

stiffness

resistance to deformation (force over change in length)

hinge joints

one axis of rotation

metacarpo-phalangeal joint

two axis of rotation

ball and socket joint

three axis of rotation

Epiphysis

ends of bone - mostly trabecular

metaphysis

between diaphysis and epiphysis

diaphysis

shaft of bone mainly compact bone

compact bone

hard and dense bone tissue (in diaphysis)

trabecular bone

spongy bone mainly in epiphysis, arranged in layered plates and reduces bone mass while maintaining strength

Bone is a two phase tissue because

this allows bone to be strong, stiff, and tough

organic layer of bone

collagen type 1, arranged in a criss cross formation

mineral layer of bone

calcium phosphate

circumferential lamallae

layers around surface of bone

osteonal

tube-like layers around a vascular channel (bone is well vascularized to supply cells)

appositional modeling

changes to bone tissue only happen on preexisting surfaces

other connective tissue

cartilage, ligament, tendon, muscle

osteoblasts

bone forming cells (become osteocyte in mineralized tissue)

chondroblast

cartilage forming cells (become chondrocyte in mineralized tissue)

fibroblasts

tendon and ligament forming cells?

chondroclasts

cartilage destroying cells

osteoclasts

Bone-destroying cells: 1) secrete H+ ions which form HCl and use lysosomes to dissolve collagen 2) reabsorb dissolved material and release in to blood

two step synthesis of bone

1. osteoblasts lay down extracellular collagen matrix 2) mineralization

mesenchyme

undifferentiated progenitor cells (mesoderm)

intramembrous bone formation

membrane changing into bone (skull and mandible)

endochondral bone formation

cartilage model as starting point

cartilage

flexible tissue that allows for both internal and surface growth (early embryonic skeletal growth is more rapid)

growth plate

allows increased in bone length via cartilage

adaptive bone remodeling

adding mass when there is more force, mostly for animals because humans peak bone mass occurs 28-30

Osteoporosis

occurs with aging, effects trabecular bone, occurs when bone resorption is faster than bone deposition

major factors affecting bone health

exercise, smoking, pregnancy, genetics, calcium

3 major systems integrating body functions

endocrine, immune, and nervous systems

endocrine glands

secrete hormones into the bloodstream

hormones

specialized chemical messengers secreted into bloodstream which travel to specific organs or cells to exert physiological control

amplification (endocrine system)

hormones secreted in small and amounts and are effective in low concentrations because of amplification due to intracellular cascades

Peptide hormone mechanisms of action

first messenger in blood and second messenger in cell, this first and second messenger situation leads to cascades

steroid hormone mechanisms of action

hormone passes into membrane and binds to receptor then this complex enters the nucleus and triggers gene transcription (gene transcription leads to amplification)

breadth (endocrine system)

breath of hormone action: broad effect

broad effect (hormone)

many cells have receptors for this hormone (thyroid hormone)

narrow effect (hormone)

only some cells have receptors for this hormone (oxytocin)

receptor selectivity (endocrine system)

hormones only act on cells that have the receptors for them

glands (endocrine system)

can secrete more than one hormone

hormones (endocrine system)

secreted by more than one gland and can have other functions in the body

permissiveness (endocrine system)

two hormones may both be needed to produce an effect

peptide/protein hormones

amino acid chains, receptors on cell membrane

steroid hormones

small lipid soluble structures that have receptors in the cytoplasm of cells