Post ICA - Nerissa Flashcards
What is gametogenesis?
Formation of gametes in gonads of males and females.
What are gametes?
Spermatozoa and ova.
What is the genetic material for gametes?
Changes from diploid to haploid.
How many chromosomes do gametes have?
23 chromosomes
Where is the site of spermatogenesis?
Testes in scrotum.
Where is the site of oogenesis?
Ova.
Why is gametogenesis important?
Sustains species.
Genetic variability.
Early embryo developement.
What happens in embryonic development during week 2?
Primordial germ cells form in epiblast.
What happens during embryonic development by the end of week 3?
Germ cells arrive in yolk sac.
What happens during embryonic development by week 4?
Germ cells migrate from yolk sac toward developing gonads.
What happens during embryonic development by the end of week 5?
Germ cells arrive at gonads.
What happens when germ cells reach the gonads?
Maturation - They undergo gametogenesis and cytodifferentiation.
What is spermatogenesis?
Production of sperm.
Where does the production of sperm occur?
Seminiferous tubules of testes.
What is production of sperm influenced by?
Androgens from leydig cells.
Are spermatogonia haploid or diploid?
Diploid.
What does 4 haploid cells develop into?
Develop into mature sperm.
What does azospermia factor on Y during molecular regulation do?
Mediate spermatogonia differentiation and spermatid maturation.
What is oogenesis?
Development of ova which occurs in the ovary.
What is the purpose of oogonia?
Replicates and forms primary oocytes.
Where are the primary oocytes contained?
Within the primary follicle.
What does primary oocyte begin?
It begins meiosis 1.
Where does the primary oocyte arrest?
Arrests in prophase 1 but stays within the primary follicle.
What happens to the primary oocyte when there is an influence of FSH and LH?
It completes meiosis 1, and forms a 2ndary oocyte with a first polar body.
What does the 2ndary oocyte begin?
Meiosis 2.
Where does the 2ndary oocyte arrest?
Metaphase 2.
Where is the 2ndary oocyte contained?
Mature/graafian follicle.
What is the cytostatic factor during oogenesis molecular regulation?
Suspension and restarting until puberty.
What is the maturation promoting factor during oogenesis?
Maturation of oocyte.
What happens at day 14 of menstrual cycle?
The Graafian follicle ruptures, releasing 2ndary oocyte.
What happens to the graafian follicle when it ruptures?
The ruptured follicle grown into corpus luteum.
What does the corpus luteum secrete?
Progesterone and estrogen.
What happens if sperm is present in fallopian tube?
Penetration of sperm and the release of LH triggers the completion of meiosis 2.
What does the 1st polar body give off?
2 more polar bodies.
What causes the formation of zygote at fertilizaiton?
The fusion of spermatozoon and nuclei of ovum.
What happens if sperm is absent in fallopian tube?
2ndary oocyte does not complete meiosis 2. Hormone levels of progesterone and estrogen decrease.
What does corpus luteum degenerates into if sperm is absent in fallopian tube?
Corpus albicans, which are absorbed into ovary.
What is ovulation stimulated by?
Surge in LH.
What happens to the estogen and progesterone if there is a surge in LH?
A decrease in estrogen.
A increase in progesterone.
Why do some women fail to ovulate?
Because of low concentrations of gonadotropins.
What needs to be administered if there is failure of ovulation due to low concentrations of gonadotropins?
Gonadotropin releasing hormone agonist drug.
If Gonadotropin releasing hormone drug is administered, what is a common side effect / complication?
Multiple ovulations = Multiple pregnancies.
Where would fertilization occur?
Ampulla of fallopian tube.
What is corona radiata?
2-3 layers, attached to zona pellucida - Supplies cell with proteins.
What is zona pellucida?
Contains a glycoprotein coat, and regulates interactions between sperm and egg.
What is vitelline membrane?
Cell membrane of oocyte.
What does the head of sperm contain?
Packets of acrosin enzyme within the acrosome.
What is the function of the centriole in the sperm?
Form flagellum and assist with sperm movement.
What does the mid-piece of the sperm contain?
Mitohondria.
What is the axoneme of the sperm?
Central strand of flagellum. composed of array of microtubules.
Movement of sperm from cervix to fallopian tube is accomplished by what?
Its own propulsion via the flagella.
What happens when spermatozoa reaches isthmus?
Becomes less motile, and cease their migration.
What is capacitation?
Period of conditioning - A glycoprotein coat and seminal plasma proteins are removed from the plasma membrane, the sperm then penetrates corona radiata.
What happens when sperm penetrates corona radiata?
Only one sperms passes corona radiata.
This sperm binds to zona pellucida - Regulated by ligand ZP3 and SP56 on acrosome.
What happens when sperms binds to zona pellucida?
There is going to be two responses - Inducing of acrosome reaction and cortical and zona reactions.
What is fast block?
Influx of Na, pH, membrane potential. Electrical charge across surface of egg.
What happens when there is an acrosome reaction?
There is a release of acrosomal enzymes (Acrosin) - Fast block (electrical barrier)
What happens when there is a release of acrosomal enzymes?
The spermatozoon penetrates ZP. The enzymes degrade the ZP
What happens when the sperm successfully penetrates the zona pellucida?
The sperm binds to specific receptors on egg’s surface, which triggers fusion of egg and sperm.
What happens during cortical and zona reactions?
These reactions are important to prevent polyspermy. Slow block - mechanical barrier.
What results in a cortical reaction?
Close contact between sperm and oocyte.
What happens in a cortical reaction?
Increase in intracellular calcium from endoplasmic reticulum.
What happens when there is an increase in intracellular calcium?
Release of lyosomal enzymes from cortical granules. Oocyte membrane becomes impenetrable to other sperm.
How do these enzymes play a role in the zona reaction?
ZP alters its structure, inactivating receptor binding site for any spermatozoon on the zona surface.
What is the zona reaction regulated by?
Zona lysin - lyosomal enzyme from acrosome.
What is the response of the secondary oocyte to entry of sperm?
2nd mitotic division.
Metabolic activation of ovum.
Explain fusion of male and female nuclei?
Nuclei come into close contact, the membrane degenerates, formation of zygote, formation of mitosis.
What are the results of fertilization?
Restoration of diploid chromosome number.
Determination of gender.
What happens in the stages of cleavage?
Zygote undergoes a series of mitotic divisions, which increases the number of cells.
Cells increase in number and decrease in size.
What happens at the 8-cell stage?
Compaction occurs.
What is compaction?
Cells clump together forming an organized structure.
What are blastomeres?
Formed when zygote undergoes cleavage. The cells that the zygote has divided into.
What do blastomeres do?
In compaction, the contact is maximized between blastomeres forming tight junctions.
What happens when tight junction are present?
Deformation of rounded shaped blastomeres.
What happens at the 16-cell stage of cleavage?
Embryo divides to form 16-celled morula.
What happens in the 16-celled morula?
Inner cells of morula has an inner cell mass.
The outer cells of morula has an outer cell mass.
What will the inner cell mass give rise to later on?
Embryoblast/embryo proper. (pluripotent).
What will the outer cell mass give rise to?
Will form the trophoblast, which will form the placenta and fetal membranes.
What happens to the morula while inner/outer masses do their thing?
Enters uterine cavity but does not attach, meaning there is no implantation. The fluid then penetrates through zona pellucida and enters the inner cell mass.
What happens when fluid enters the spaces in the inner cell mass?
Results in a single cavity called a blastocele.
What happens when there is formation of blastocele?
The morula undergoes mitosis to form what is called an early blastocyst.
What happens to early blastocele when zona pellucida disappears?
Outer cell mass flattens to form the cells wall of blastocyst.
Inner cell mass (embryoblast) are situated one pole of blastocyst.
What happens when early blastocyst undergoes mitosis?
Formation of late blastocyst.
What is the importance of zona pellucida?
Protection during growth and transport.
Promotes implantation.
What does the zona pellucida prevent?
Abnormal implantation.
Polyspermy.
Rejection from embryo.
Breakage of blastomeres.
What allows attachment an invasion of trophoblast?
Integrins expressed by trophoblast.
What does the extracellular matrix produce?
Laminins (promotes attachment).
Fibronectin (stimulates migration.
What happens at the time when implantation occurs?
Changes in composition and appearance of endometrium.
Cells of embryoblast differentiate into 2.
What has the embryoblast differentiated into?
Layer of columnar cells - Epiblast layer.
Layer of cuboidal cells - Hypoblast layer.
What forms the bilaminar disk?
Epiblast and hypoblast.
What regulates trophoblast differentiation?
Laminin. integrin and fibronectin.
What is histiotrophic nutrition?
Spaces formed in syncytiotrophoblast called lacunae.
Lacunae circulates maternal blood.
Lacunae filled with fluid - Histiotrophic nutrition.
What happens by the end of week 2?
Implantation is complete - late blastocyst is buried inside endometrium.
What are the layers of the wall of uterus?
Endometrium.
Myometrium.
Perimetrium.
What are the stages that endometrium passes through?
Proliferative/follicular phase.
Secretory phase.
Menstrual phase.
What happens in the proliferative phase?
Regenerative layer. Prepares for potential implantation.
This phase is under the influence of estrogens and parallels growth of follicles.
What happens in the secretory phase?
The ‘implantation window’.
Increase in progesterone levels.
If no implantation, then menstrual stage starts.
What happens in the menstrual stage?
Period, blood escapes from superficial arteries.
What is an ectopic pregnancy?
Implantation abnormality.
Inflammation of fallopian tube.
What causes an ectopic pregnancy?
Endometriosis.
Scar tissue from previous surgery.
Hormonal imbalance.
What are the risks associated with an ectopic pregnancy?
Haemorrhage - Excess blood can compress organs and cause dysfunction. (haemorrhage shock)
Accumulation of blood inferior to diaphragm - irritation to nerves.
Abnormal vaginal bleeding.
What is the cavity that appears in the epiblast?
Amniotic cavity.
What are amnioblasts?
Epiblast cells near cytotrophoblast. They line the amniotic cavity.
What do the cells that come form hypoblast form?
Thin membrane - Exocoelomic membrane. Lines the inner surface of cytotrophoblast. This forms the primitive yolk sac.
What is the extra-embryonic mesoderm?
Cells that appear from the primitive yolk sac.
What happens in the extra-embryonic mesoderm?
Large cavities develop.
Clumping of these cavities forms the extra-embryonic coelom/chorionic cavity.
What does the connecting stalk become?
The umbilical cord.
What is hemotrophic nutrition?
Only active when placenta is established.
Primary, secondary, and tertiary villi.
What is primary villi in the hemotrophic nutrition?
Extensions of cytotrophoblast to syncytiotrophoblast.
Hypoblast cells form the secondary/definitive yolk sac.
What is the secondary villi in hemotrophic nutrition?
Complex structure of primary villi.
Characterized by presence of extra-embryonic mesoderm.
What is the tertiary villi in hemotrophic nutrition?
Blood cells and vessels.
Undergoes branching - Placental transfer.
Formation of capillary system.
What is assisted reproductive technology?
Fertility treatment.
In vitro fertilization.
Intra tubal transfer of gametes.
Intra tubal transfer of zygotes.
Surrogacy.
What is gastrulation?
The formation of the 3 germ layers (endoderm, mesoderm and ectoderm = Trilaminar disc).
What can be explained as the beginning of morphogenesis?
The establishment of main organ systems.
Growth anteriorly to posteriorly.
What is neurulation?
When the brain takes control.
Formation of nerve tissues.
What does caudal mean?
Towards foot.
What does cranial/cephalic mean?
Towards head.
Where did the secondary yolk sac come from?
Came from hypoblast.
What is a primitive streak?
Middle of embryonic disc - extends from posterior to anterior.
It is where gastrulation begins
What is formed in the cranial end of the primitive streak?
Primitive node.
The formation of primitive node and maintenance is maintained by what?
HNF-3 B.
What is the small depression in the primitive node called?
Primitive pit.
What is the opening that is near the cranial end in the hypoblast layer?
Buccopharyngeal/Oropharyngeal membrane.
What is the opening that is near the caudal end of the hypoblast layer?
Cloacal membrane/prechordal plate.
The cells from the primitive streak secret what?
Fibroblast growth factor 8. (FGF8).
Why do epiblast cells move under the primitive groove in the primitive streak?
Because they lose their adhesion molecules.
What happens when epiblast calls invaginate into primitive groove?
Mesoderm is formed.
When the invaginated epiblast cells move they displace the hypoblast, what do they create?
Endoderm.
What do the remaining cells in the epiblast form?
Ectoderm.
What do the three germ layers form?
Trilaminar disc.
How does the notochord form?
When mesenchymal cells fold inward and forms a solid cord.
What are the functions of the notochord?
Influences embryonic folding.
Secretes sonic hedgehog protein.
Induces neurulation.
How does neurulation happen?
Ectodermal cells thicken in midline.
These cells break apart from ectodermal layer to form neural tube and crest.
What happens during activation of BMP-4 activity?
Ectoderm (epidermis) and mesoderm (intermediate and lateral plate) are ventralized.
What happens during inactivation of BMP-4 activity?
Mesoderm is dorsalized.
Ectoderm is neuralized.
Which proteins inactivate BMP-4 activity to neuralize ectoderm in the cranial part to give rise to forebrain and midbrain?
Noggin, chordin, and follistatin.
Which proteins inactivate BMP-4 activity to neuralize ectoderm in the caudal part hindbrain and spinal cord?
WNT-3a and FGF.
What are the two types of gastrula folding?
Cephalo-caudal direction.
Transverse direction.
What is sacrococcygeal hematoma?
Benign tumour.
Result of incomplete differentiated germ layers
What do nerve cells exhibit?
Electrical excitability - Response to stimuli, generating an impulse.
What is a general characteristic of nerve cells?
That they have a selective permeability - Deprivation of oxygen can cause nerve cell death.
Where are neurones derived form?
Embryogenesis - Primitive streak.
What are the two types of cells in the nervous system?
Neurons.
Neuroglia.
What are neurons further classified as?
Bipolar, unipolar, and multipolar types.
And according to their function (sensory, motor and interneurons).
What are the three characteristic components of a neuron?
Cell body.
Dendrite.
Axon.
Explain the cell body of the neuron?
Perikaryon, the cytoplasm contains a mitochondria, golgi apparatus, lyosomes, microtubules and neurofilaments.
Explain the dendrites of the neuron?
Receive stimuli from other neurons, increase surface area of neuron, are unmyelinated.
Explain the axon of the neurone?
Only one axon, convey info form one cell to the other.
What is the region between axon hillock and beginning of myelin sheath known as?
Initial segment. This is where action potential is generated.
Where are neurotransmitters found?
In terminal boutons.
What does the dendrite lack?
Golgi apparatus.
What does the axon hillock lack?
Nissl bodies and golgi apparatus.
What is nissl bodies stack of?
Rough endoplasmic reticulum with ribosomes.
What are the basic type of neurones?
Anaxonic/Amacrine.
Bipolar.
Pseudounipolar/Unipolar.
Multipolar.
What is an anaxoinic/amacrine neuron?
Many dendrites but no axon.
Found in retina and olfactory receptors.
What is a bipolar neuron?
Has only one axon and one dendrite.
Found in ocular, auditory, and olfactory special senses.
What is a pseudounipolar/unipolar neuron?
One axon that divides close to the cell body into 2 axons.
What is a multipolar neuron?
One axon and 2 more dendrites. Most abundant neuron.
What is Parkinson’s disease?
Genes an environmental triggers play a role.
Apoptosis of dopamine producing neurons.
Affects muscular activity.
What is Parkinson’s treated with?
L-dopa.
What are neuroglia?
Supporting cells of NS.
Holds neurons in place.
Supplies oxygen.
Forms myelin.
Destroys pathogens.
What are the types of central neuroglia?
Astrocytes.
Oligodendrocytes.
Ependymal cells.
Microglia.
What are astrocytes?
Largest neuroglia.
Morphologically heterogeneous.
Modulate neuronal activities by providing potassium concentration in the extracellular space of brain.
What are oligodendrocytes?
Production and maintenance of myelin.
What are microglia?
Possess phagocytotic activities.
What are ependymal cells?
Allows absorption of CSF.
Modified ependymal cells produce CSF.
What are the types of peripheral NS?
Satellite cells.
Schwaan cells.
What is a satellite cell?
Helps maintain a controlled microenvironment.
What is a schwaan cell?
Support and nurture myelinated and unmyelinated nerve cell fibres.
What are demyelinating diseases?
Multiple sclerosis.
Guillain-Barre syndrome.
What is multiple sclerosis?
Immune mediated destruction of myelin in CNS.
Symptoms relate to affected white matter.
What is Guillain-Barre syndrome?
Immune mediated destruction of myelin in PNS.
Linkage to resp or gastro infections.
Weakness of limbs and resp muscles.
What is a peripheral nerve?
May contain afferent or efferent nerve fibres.
Epineurium.
Perineurium.
Endoneurium.
What is epineurium?
Surrounds peripheral nerves and fills spaces between fascicles. Blood vessels travel in it.
What is perineurium?
Surrounds a fascicle of nerve fibres. Blood vessels transverse to it.
What is endoneurium?
Surrounds each nerve fiber, poorly vascularized.
What are two patterns of peripheral neuropathy?
Damage to schwaan cells - Demyelinating neuropathy.
Damage to axons - Axonal neuropathy.
What are ganglia?
Relay stations.
Spiral ganglia.
Sympathetic ganglia.
Parasympathetic ganglia.
What is spiral ganglia?
Each cell body is surrounded by a layer of flattened satellite cells.
What is sympathetic ganglia?
Separated by axons and dendrites.
Lipofuscin granules.
Less satellite cells and irregularly placed.
What is parasympathetic ganglia?
Few cell bodies clumped with each other and satellite cells within supporting connective tissue.
What does connective tissue consist of?
Extracellular matrix
Cells - 1. Defence and immune functions, 2. Synthesis, maintenance, and metabolic activity.
What are constituents of the extracellular matrix?
Hyaluronic acid and proteoglycans.
What are the types of embryonic connective tissue?
Mesenchyme.
Mucoid.
What are the types of mature connective tissue?
Specialised - Reticular, Adipose, Cartilage, Bone, and Blood.
Connective Tissue Proper - Loose areolar, Dense irregular, and Dense regular.
What is the mesenchyme CT?
Processes make contact at gap junctions.
Collagen type 3 fibres.
What is the mucoid/mucous CT?
Wharton’s jelly.
Resemble fibroblasts.
Found in fetal umbilical cord.
What is loose areolar CT?
Present in Lamina propria, supports epithelia - Breach of epithelia = Immune reactions.
More ground substance than fibre.
Permeable to oxygen, water and other molecules.
What is dense irregular CT?
Irregular interwoven pattern.
Found in capsules of organs, submucosa of hollow organs and dermis of skin.
What is dense regular CT?
Arranged in parallel pattern.
Found in tendons, ligaments, fascia and aponeurosis.
What is reticular CT?
Type 3 collagen fibres.
Provides structural support.
Found in stroma of non-tubular organs. (spleen, liver, kidney).
What is adipose CT?
Aggregations of adipocytes.
Vascularized.
What is white adipose CT?
Throughout body and deep layers of skin.
Large adipocytes.
Nucleus and cytoplasm are pushed against membrane.
Triglyceride storage.
Padding - shock absorber.
What is brown adipose CT?
Around adrenal glands.
Small adipocytes.
Many mitochondria and central nucleus.
Thermogenesis.
Body temperature regulation.
What is cartilage CT?
Firm but somewhat flexible.
Sparse chondrocytes.
Large ratio of GAG - permits diffusion = tissue viability.
What are the three types of cartilage?
Abundant ground substance.
Abundant collagen fibres.
Abundant elastin fibres.
Where is abundant ground substance cartilage found and what is its function?
Articular surface of synovial joints, ribs, epiphyseal plates of long bones.
Lubricates synovial joints.
Where is abundant collagen fibre cartilage found and what is its function?
Intervertebral discs.
Pubic symphysis.
Menisci of knee.
Shock absorber.
Where is abundant elastin fibre cartilage found and what is its function?
Larynx.
External ear.
Epiglottis.
Flexibility.
What is bone CT?
Calcified extracellular matrix.
Organic - Predominant collagen type 1.
Inorganic - Calcium hydroxyapatite.
Protects organs.
Calcium reservoir.
Hematopoiesis.
What is woven bone?
Immature.
Randomly oriented fibres in osteoid.
Healing a fracture, remodelled into lamellar bone.
What is lamellar bone?
Mature bone.
Fibres in parallel arrays.
Physically stronger and more resilient.
Subdivided into cortical and cancellous.
What is cortical/compact bone?
Heavy and tough.
Periosteum (dense regular)
Endosteum (loose CT)
Multiple osteons that surrounds marrow cavity.
What does the haversian canal contain?
Blood vessels, nerves and lymphatics.
What does volkman’s canal contain?
Within lamellae. Osteocytes within lacunae.
Canaliculi connect lacunae and osteocytes.
What is cancellous/spongy bone?
No osteons.
Lighter.
Lamellae arranged in lattice-like pattern.
What is blood CT?
Viscous fluid like - blood plasma.
Erythrocytes.
Leukocytes.
Platelets.
Tissue damage, and spaces left after injury are replaced by what type of CT?
Dense irregular scar tissue.
What is a growth beyond boundaries of tissue called
Keloid.
