Human Development Anatomy Flashcards
What is the lumbrosacral trunk?
Where fibres from L4 and all of L5 join, this emerges medial to psoas major and runs inferiorly over the pelvic brim and joins the sacral plexus
What type of outflow is present in the parasympathetic nervous system?
Cranio-sacral: cranial (CN III, VI, IX and X) and sacral (S2,3,4; pelvic splanchnic nerves)
Where do the ovarian arteries originate?
Branches from the abdominal aorta and arise from L2 region
What is the blood supply to the uterus and vagina?
Uterine and vesicular arteries (branches of the internal iliac)
What is the inguinal canal?
Space that passes obliquely through the abdominal wall in the inguinal region, and is found over the medial half of the inguinal ligament
What are the openings at each end of the inguinal canal?
Deep (internal) ring and the superficial (external) ring
Describe the deep (internal) ring of the inguinal canal
An opening in the transversalis fascia and is located at the midpoint of the inguinal ligament. This is the point halfway between the ASIS and the pubic tubercle.
Describe the superficial (external) ring of the inguinal canal
An opening in external oblique aponeurosis. It is located above the pubic tubercle.
What does the inguinal canal contain in males?
Vas deferens, testicular vessels and ilioinguinal nerve
What does the inguinal canal contain in females?
Round ligament of the uterus and ilioinguinal nerve
What forms the walls of the inguinal canal?
Anterolateral muscles of the abdominal wall (external oblique, internal oblique and transversus abdominis) and their aponeuroses
What are the boundaries of the urogenital triangle?
Roof = pelvic diaphragm (levator ani and coccygeus muscles) Walls = narrow walls of the pelvic cavity below the attachment of the levator ani muscle. Posterior = perineal body
What are the two divisions of the perineum?
Urogenital and anal triangles
What does the deep perineal pouch contain in females?
Proximal part of the urethra, mass of smooth muscle and dorsal neurovasculature of the clitoris
Where does the superficial perineal pouch lie?
Between the perineal membrane and the membranous layer of the superficial fascia is the superficial perineal pouch, which contains the erectile tissues of the clitoris and associated skeletal muscles
What are the contents of the superficial perineal pouch in women?
Clitoris and associated muscle (ischiocavernosis), bulbs of the vestibule and surrounding muscle (bulbospongiosis), greater vestibular glands, deep perineal branch of internal pudendal vessels and nerve, superficial transverse perineal muscle
What is the anorectal ring?
the junction of the rectum, anal canal, the internal sphincter, the deep part of the external sphincter and the puborectalis muscle form the anorectal ring
Describe the internal anal sphincter
Involuntary sphincter
Describe the external anal sphincter
Voluntary sphincter and the puborectalis fibres of the levator ani blend with the deep fibres of the external sphincter
Describe the descent of the testes in development
Testes develop high on posterior abdominal wall –> descend through the inguinal canal in the anterior abdominal wall and into the scrotum of the perineum.
What is the tunica vaginalis?
The serous covering of the testis
What is the tunica albuginea?
The fibrous covering of the testis, superficial to the tunica vaginalis
Which artery supplies the testis and from which vessel does it branch?
Testicular artery from the abdominal aorta
Which vein drains the testis, and into which vessels does this then drain?
Testicular vein and this drains into the IVC on the right side and the left renal vein on the left side
How is the pampniform plexus involved in regulating the testicular temperature?
It’s a network of very small veins in the spermatic cord which act as a heat exchanger too cool blood in adjacent arteries
Describe the path of the vas deferens
Begins at tail of epididymis (superior pole) –> ascends testis medial to epididymis –> spermatic cord –> inguinal canal –> crosses external iliac vessels –> passing between ureter and bladder –> medial to seminal vesicles –> joins seminal vesicle duct to form ejaculatory duct –> urethra
Describe the 3 coverings of the peritoneal outpouching formed by the tunica vaginalis
Transversalis fascia (deepest), musculature of internal oblique, aponeurosis of external oblique (superficial)
Describe the gubernaculum
Helps descent of testis and extends from the inferior border of the developing gonads to the labioscrotal swellings
Why are there no parasympathetic fibres in the spermatic cord?
Because only sympathetic innervation is used in ejaculation
Describe the pouch of Douglas in females
Deep recto-uterine pouch (posteriorly between the uterus and rectum), and is the lowest point in the female pelvis
What is the trigone in the bladder?
Smooth triangular area between the openings of the ureters and urethra on the inside of the bladder
Describe the structure of the bladder
Apex directed towards top of pubic symphysis, base of bladder shaped like inverted triangle (faces posteroinferiorly)
Which muscles ‘cradle’ the inferolateral surfaces of the bladder?
Cradled between the levator ani muscles of the pelvic diaphragm and the adjacent obturator internus muscle
What is the infundibulum?
Expanded trumpet-shaped end of uterine/Fallopian tube
What is the fimbriae?
Finger-like projections on the end of the Fallopian tube
What is the ampulla of the ovary?
The stem of the Fallopian tube that carries eggs to the uterus
Describe the broad ligament
Peritoneal fold that suspends the uterus and the uterine tubes
Describe the ovarian suspensory ligament
Suspends the ovaries from the lateral pelvic wall
Describe the ovarian ligament
Tethers the ovary to the uterus
Describe the round ligament
Connects the uterus to the labia majorum via the inguinal canal
How does the course of the ovarian vein differ on the left compared to the right?
On the right it ravels through the suspensory ligament of the ovary to the IVC, on the left it joins the left renal vein (NOT IVC)
Describe the structure of the clitoris
Composed of two corpora cavernosa and the glans clitorisl embedded in the connective tissue of the perineum (superficial pouch).
Describe the location of the vestibular glands in females
Either side of vaginal opening are the bulbs of the vestibule, and posterior to the bulb of the vestibule are the greater vestibular glands (Bartholin’s gland)
Where is the S3 dermatome located?
Innermost thigh
Where is the S4 dermatome located?
Encircles anal triangle
Where is the S5 dermatome located?
Encircles the external anal sphincter
What are the three terminal branches of the pudendal nerve?
Inferior rectal nerve, dorsal nerve of penis/clitoris and perineal nerve
What supports the uterus to prevent prolapse?
Levator ani muscles, ligaments (transverse cervical, pubocervical and sacrocervical)
What are the main events in week 1 of embryological development?
Fertilisation, cleavage, blastocyst formation, implantation
What is the cortical reaction in fertilisation?
Where the penetration of the sperm into the oocyte stimulates a reaction rendering the secondary oocyte impermeable to other sperm
What is a blastula?
When the zygote cytoplasm is successfully cleaved, resulting in smaller blastomeres
What is a morula?
Mulberry-looking cell at the 16-32 cell stage which has an inner and outer cell mass
When does blastocyst formation occur?
When fluid secreted within the morula becomes the blastocyst cavity
What is an ectopic tubal pregnancy?
When the zygote doesn’t implant in the uterus, but does so elsewhere
What is gastrulation?
A process that establishes the three primary germ layer (ectoderm, mesoderm
and endoderm), thereby forming a trilaminar embryonic disk.
What is neuralation?
Formation and closure of the neural tube
What does the notochord form in adults?
Nucleus pulposus of the IV disc
Name the three primary brain vesicles
Prosencephalon (forebrain), mesencephalon (midbrain) and rhombencephalon (hindbrain)
Name the five secondary brain vesicles
Telencephalon (forebrain), diencephalon (forebrain), mesencephalon (midbrain), metencephalon (hindbrain), myelencephalon (hindbrain)
Describe the adult brain structures that arise from the telencephalon
Cerebrum and the lateral ventricles
Describe the adult brain structures that arise from the diencephalon
Thalamus, epithalamus, hypothalamus, retina and third ventricle
Describe the adult brain structures that arise from the mesencephalon
Midbrain and cerebral aqueduct
Describe the adult brain structures that arise from the metencephalon
Pons, cerebellum and fourth ventricle
Describe the adult brain structures that arise from the myelencephalon
Spinal cord and central canal
What is the significance of elevated α-Fetoprotein defects?
Elevated AFP levels are associated with neural tube defects and oesophageal or duodenal atresia
What is the significance of reduced α-Fetoprotein defects?
Associated with Down’s Syndrome
Define atresia
Absence or abnormal narrowing of an opening or passage in the body
Outline the transition between four sites of haemopoiesis in foetal development
Blood cell formation first occurs within the extraembryonic mesoderm around the yolk sac during week 3 of development. Beginning of week 5, haemopoiesis is taken over by a sequence of embryonic organs: liver, spleen, thymus and bone marrow
What does the heart develop from?
Areas in the mesoderm known as heart forming regions (HFR)
Name the five dilations that are evident along the length of the primitive heart tube
Sinus venosus, primitive atrium, primitive ventricle, bulbus cordis and truncus arteriosus
What does the sinus venosus become in an adult?
Incorporated into the right atrial wall in order to form the smooth part called the venarum sinus as well as the SAN and coronary sinus
What does the primitive atrium become in an adult?
Left and right atria
What does the primitive venrticle become in an adult?
Ventricles (provides trabeculated parts of ventricular walls)
What does the bulbus cordis become in an adult?
Right ventricle (provides smooth part)
What does the truncus arteriosus become in an adult?
Aorta and pulmonary trunk
Where is the blood entering the single heart tube?
The bottom
Describe the main events that lead to the closing of the foramen ovale
Drop in pulmonary vascular pressure due to beginning of breathing –> greater pO2 –> ductus arteriosus closure –> causes pressure drop in the right atrium –> no force exerted on foramen ovale –> no blood shunting
What does mesoderm differentiate into?
Muscles and arteries
What do neural crest cells differentiate into?
Bone and connective tissue
What are pharyngeal pouches?
Evaginations of endoderm that lines the foregut (e.g. oral cavity and oesophagus)- internal
What are pharyngeal grooves (clefts)?
Invaginations of ectoderm located between each pharyngeal arch – external.
What are pharyngeal membranes?
Structures consisting of ecto-, meso- and endoderm and neural crest cells located between each pharyngeal arch.
Outline the cranial nerves that supply the 4 pharyngeal arches
1st arch = CN V
2nd arch = CN VII
3rd arch = CN IX
4th arch = CN X
Which arch, pouch, groove & membrane contribute to the ear canal?
1,1,1
Which pharyngeal arch forms the anterior 2/3rds of the tongue?
Pharyngeal arch 1
Which pharyngeal arch forms the posterior 1/3rd of the tongue?
Pharyngeal arches 2-4
What three swellings make up the face?
The frontonasal prominence, the maxillary prominence and the mandibular prominence
What does the medial nasal prominence become?
Upper lip and nose
Which pharyngeal arch do the maxillary and mandibular prominence come from?
Pharyngeal arch 1
What is the intermaxillary segment?
Forms when the medial growth of the maxillary prominence pushes the two medial nasal prominences together at the midline. The intermaxillary segment forms the philtrum of the lip, four incisor teeth and the primary palate.
Describe the secondary palate
Forms from outgrowth of the maxillary prominences called the palatine shelves; initially the shelves project downward either side of the tongue but then attain a horizontal position and fuse along the palatine raphe to form the secondary palate.
Where do the primary and secondary palate fuse?
At the incisive foramen to form the definitive palate
Name the four fontanelle of the skull
Mastoid (by ear), sphenoid (closer to temples), anterior (top of head) and posterior (right at back of the head)
