Embryology Flashcards
Ectoderm derivatives
Mesoderm derivatives
MESODERMAL CELLS
Myeloid stem cells
Erythroid stem cells
Spleen
gOnads
Dermis
Entire trunk
Renal system
Meninges (DURA only)
Adrenal cortex
Lymphoid stem cells
CVS
Endothelium (BVs and heart)
Lining of the body cavities (visceral and parietal)
Limbs and LNs
Smooth muscles of GIT
Endoderm derivatives
Epithelial lining of GIT
Neck - thyroid, PT, thymus (endocrine)
Drainer - bladder, urethra
Organs assoc with GI tract
Dangerous liver
Eustachian tube
Respiratory tract
Middle ear
MAC lost a pair of PANTs at the CAMPP.
MAC (adrenal cortex)
Mesoderm: adrenal cortex
PINT (Parathyroid, eNdoderm, thyroid)
Endoderm: thyroid/thymus, parathyroid
CAMPP (eCtoderm, adrenal medulla, pos pit)
Ectoderm: pituitary, adrenal medulla
Mesoderm sections
Lateral plate: skeleton of extermities (limbs)
Intermediate plate: Kidneys and gonads (urogenital system.. other than epithelium which is endo)
Paraxial: Axial skeleton (somites become vertebral column)
Skeletal system derivatives
Lateral plate mesoderm: forms limb skeleton (Lateral = Limbs)
Paraxial mesoderm: forms axial skeleton (vertebrae)
Neural crest (from ECTODERM): forms cranial skeleton
Embryonic development of fingers and toes from the limb buds involves apoptosis of cells between individual digits. What are the steps of apoptosis?
(1) Cell shrinkage: Cell cytoplasm condenses and organelles tightly packed
(2) Pyknosis: Chromatin condensation
(3) Blebbing: Small blebs in the plasma membrane form
(4) Budding: Formation of apoptotic bodies - portions of cytoplasm and intact organelles with or without DNA. Budding prevents release of cellular contents into the surrounding interstitium. Plasma membrane remains intact
(5) Phagocytosis: Macrophages quickly engulf apoptotic bodies. They do not release cytokines so there is no inflammatory response
Necrosis steps
2 pathways
The first of these two pathways initially involves
1. Oncosis (swelling of the cell)
2. Blebbing
3. Pynknosis (nuclear shrinkage)
4. Karyolysis (nuclei are dissolved into the cytoplasm)
The second pathway is a secondary form of necrosis that is shown to occur after apoptosis and budding.[21] In these cellular changes of necrosis, the nucleus breaks into fragments (known as karyorrhexis).
Apoptosis Vs. Necrosis
While both necrosis and apoptosis are mechanisms involved in multicellular organism cell death, there are multiple ways in which they can be differentiated. Apoptosis is viewed as a naturally occurring process while necrosis is a pathological process. Pathological processes are caused by toxins, infections, or traumas, and are often unregulated. Apoptosis is both regulated and timely, making it predictable and healthy for the host.
The difference between apoptosis and necrosis can also be seen in the following factors:
Process – Apoptosis involves the shrinking of cytoplasm, resulting in the condensation of the nucleus. Necrosis happens when cytoplasm and mitochondria swell up to cause cell lysis, or a rupture in the cell membrane.
Membrane Integrity – A hallmark trait of apoptosis is blebbing. Blebbing occurs when the cytoskeleton of a cell breaks down and the membrane bulges outward. Apoptotic blebs can form when little capsules of cytoplasm detach from the dying cell. This does not damage the integrity of the membrane. During necrosis, the integrity of the membrane is loosened and therefore decreased significantly if not totally lost.
Organelle Behavior – Organelles can still function even after the apoptotic cell death of a cell. During necrotic cell death organelles swell and disintegrate. Organelles are not functional after necrosis.
Caspase – Caspases are proteolytic enzymes that help control cell death and inflammation. Apoptosis depends on caspases while necrosis does not.
Scope of Affected Cells – Apoptosis is localized and only destroys individual or single cells. Necrosis can spread to affect contiguous cell groups, causing damage beyond the initial area.
Bodily Influence – Apoptosis is involved in controlling cell numbers and is often beneficial. However, if apoptosis becomes abnormal in either direction, it may cause diseases. Necrosis on the other hand is always harmful and can be fatal if left untreated.
Functions of the yolk sac during early embryonic development:
Gas and nutrient exchange
Primordial germ cell production
Primitive haematopoiesis
Protein synthesis
Excluding the epithelium, which germ cell layer does the urogenital system originate?
Intermediate mesoderm
Summary of Germ Layer Contributions to the GI tract
Endoderm: mucosal epithelium, mucosal glands, and submucosal glands of the GI tract.
Mesoderm: lamina propria, muscularis mucosae, submucosal connective tissue and blood vessels, muscularis externa, and adventitia/serosa
Neural crest: neurones and nerves of the submucosal and myenteric plexus
Pharyngeal arches and arteries
Arch 1 – Maxillary arteries, ext carotid
Arch 2 – regresses (except stapedial artery)
Arch 3 – Internal carotid & common carotids
Arch 4 – R forms R subclavian; L forms arch of aorta
Arch 5 –regresses
Arch 6 – Pulmonary arteries. L forms ductus arteriosus
Weeks of develipment
Heart
Lung
RBCs
Pancreas insulin
Larynx
Bile made
Alveoli
Can breathe independently
Heart starts developing week 3
Lung development starts week 4
RBCs start developing week 6 (in liver – haematopoetic tissue=mesoderm). Hepatocytes = endoderm
Haematopoesis by the liver until 8 months, then bone marrow takes over month 9
Pancreas starts secreting insulin week 10
Larynx formed by week 12
Bile starts being made week 12
Alveoli develop week 24
Can breathe independently by week 28
ant vs post pituitary
anterior pituitary from surface ectoderm epithelial tissue of nasal cavity à Rathke’s pouch à anterior pituitary
Post pit from neural tube ectoderm
Ectoderm: Epithelial tissue (external and orifices)
Surface ectoderm - epidermis (skin), nails, hair, sweat glands, oral cavity, ear canal, inferior 1/3 anus below the pectinate line nasal cavity (except roof = olfactory placode)
The cloacal membrane
The area of ectoderm:endoderm contact (with no mesodermal tissue) at most caudal end of the developing embryo.
The cloaca bifurcates
ANT: Urogenital sinus -> Urethra, bladder (prostate gland in males)
POST: Anal canal (posteriorly): Superior 2/3 above the level of the pectinate line
allantosis what does it end up becoming?
The allantois (original drainage of the cloaca) -> URACHUS (remnant of the channel that did exist between the bladder and umbilicus for urinary/waste drainage in the first trimester) -> MEDIAN UMBILICAL LIGAMENT
Gubernaculum remnants:
Males – scrotal ligament, attaches scrotum to inferior testes
Females – ovarian ligament (uterus – ovary) and round ligament (uterus – labia)
Gene expression of note in embryology of the male and female reproductive tracts
SRY gene presence -> production of TDF (testes determining factor) -> development of male gonads (through growth of mesonephric/Wolfian ducts)
((Sertoli cells -> Mullerian inhibitory hormone/ AMH -> inhibits paramesonephric/ Mullerian duct development)
SOX-9 in males – chromosome 17 -> role in testicular development, silenced in females
WNT-4 in females – chromosome 1 -> role in ovarian development, silenced in males
Ambiguous genitalia/ immature testicular development can arise in XY individuals with non-silenced/ extra copy of WNT-4 gene
Damage to/ lack of WNT-4 gene in XX individuals -> Mullerian agenesis / masculinisation
Development of external genitalia
Guided by DHT in males / oestrogen in females:
Genital tubercle -> Erectile tissue development
Female clitoris/ vestibular glands
Male glans penis and corpus spongiosum/ cavernosum
Labioscrotal swellings
Male scrotum
Female labia majora
Urogenital sinus
Male prostate gland, prostatic urethra, membranous urethra and Cowper’s /bulbourethral glands
Female paraurethral glands, Bartholin’s glands and female urethra
Urethral folds
Male penile shaft and penile urethra
Female labia minora
Pharyngeal apparatus
Week 4
Pharyneal arches (mesoderm)
Pharyneal cleft (ectoderm)
Pharyneal pouch (endoderm)
Pharyngeal arches
1
CN3 (mandibular breanch)
Everything we need to chew
Mal and inkUs
2
CN7
Facial expression
Stapes and stapedius
3
CN 9 Glossopharyngeal
4
CN 10 Vagus (sup laryngeal)
Make food go down the right way and produces speach
6
CN 10 Vagus (recurrent larynhgeal)
produces speach
Tongue = 3 arches
Ant 2/3 FIRST ARCH
Post 1/3 THIRD AND FOURTH ARCHS
Pharyngeal clefts
1 helps to form the ear (external aud meatus and ear drumbs)
2-4 fade as embryo grows
