FAB Lower Limb Exam Questions and Answers set PDF

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Summary

A set of questions and answers for the Lower Limb sessions of the FAB Cambridge Anatomy course....

Description

FAB Questions – March Embryology of the GI tract 

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Formed in 4th week of intrauterine life o Head o Tail o Lateral folds incorporate dorsal part of yolk sac into embryo – ie folds over. 3 parts: o Foregut  Ends PRECISELY at point which hepatic bud forms.  Coeliac plexus

Foregut Pharynx Oesophagus Larynx

Respiratory tract

Atresia Stenosis Tracheoesophageal fistula Hoxa3 TF

Stomach

Liver

Duodenum up to Sphincter of Oddi.

Differen tial growth

BMPs

Annular pancreas

Pyloric stenosis

HNF3

PDX1

Pdx1 TF

HNF4

PAX1

FGF2

Hoxb4 TF

o

o

Retroper

PAX6 

o

Pancreas

Respiratory tract forms from respiratory diverticulum  As it grows a tracheoesophageal septum is formed.

 Midgut  Starts where hepatic bud forms.  Later this becomes Sphincter of Oddi in 2nd part of duodenum.  The junction with the hindgut not distinguishable.  Superior mesenteric artery Hindgut  Defined as 2/3 along transverse colon in adult.  Inferior mesenteric artery All arteries reach gut via dorsal mesentery.  Dorsal mesentery derived from visceral layer of lateral plate mesoderm.

Biliary tree

Regionalisation  Differentiation of the gut tube regulated by interactions between gut endoderm and mesoderm. o Mediated by sonic hedgehog (SHH)  SHH upregulates factors in mesoderm that then deterimine type of structure formed from gut tube.  Establishes nested expression of HOX genes.  EXAMPLE = in hindgut, SHH expression establishes nested expression of Hox genes in mesoderm. Once mesoderm specified this then directs endoderm.  Retinoic acid (RA) increasing caudally (colon has highest [RA], pharynx lowest [RA]). Stomach  Differential growth in its walls and position causes rotation around longitudinal and antero-posterior axes. o Ventral border (front)  Lesser curvature o Dorsal border  Greater curvatuve o Dorsal mesogastrium  Greater omentum (including lienorenal and gastrosplenic ligaments) o Rotation around longitudinal axis produces space at back = lesser sac. o Left surface  anterior (front left vagus) o Right surface  posterior surface (sup. By right vagus) o “GET RIGHT BACK, ONLY FRONT LEFT.”  Also duodenum fuses with peritoneum of post. Abdo wall (secondary retroperitoneal) whilst liver is also enlarging  reduces lesser sac entrance to epiploic foramen. Spleen Spleen is formed in the greater omentum by LATERAL PLATE MESODERM. Liver  Forms from: o Hepatic bud-endoderm of primitive gut lining  Forms biliary tract (incl. hepatocytes) and gall bladder  Signalled by cardiac mesoderm (FGF2) and septum transversum (BMPs). o Vitelline/umbilical veins form the sinusoids of liver.  ALL FOREGUT ENDODERM HAS POTENTIAL TO DIFFERENTIATE TO LIVER o This is inhibited by factors produced by surrounding tissues. o These inhibitors are blocked in liver region by FGF2 (fibroblast growth factor 2) secreted by cardiac mesoderm and blood vessels adjacent to hepatic bud. o Bone morphogenetic proteins (BMPs) secreted be mesoderm of septum transversum enhance sensitivity to FGF2. o Endoderm differentiation to hepatocytes and biliary mediated by:  HNF3  HNF4 (hepatocyte nuclear transcription factors)  Function of foetal liver: o Relatively large size of liver in foetal life due to maematopoiesus.  Fills most of abdo cavity pushing out midgut into umbilicus. o Starts to secrete bile @ 12th week. Pancreas  Initially an outgrowth of hepatic bud  forms ventral pancreas  uncinate process + inferior part of head of pancreas (empties via minor pancreatic duct).  Main part from gut tube  dorsal pancreas  Upper head, neck, body, tail (drained by main pancreatic duct)  Ventral head rotates round o Failure to rotate results in annular pancreas

Midgut o

Midgut    

Starts where hepatic bud forms. Later this becomes Sphincter of Oddi in 2nd part of duodenum. The junction with the hindgut not distinguishable. Superior mesenteric artery

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A persistent vitelline duct that fails to close is a MECKEL’S DIVERTICULUM.

Midgut abnormalities

Midgut Primary intestinal loop

Omphalocele

Gastroschisis

Meckel's Diverticulum

The Caudal limb

Cephalic limb

Failure in recanal

Atresia

Lower duodenum

Lower ileum

Cysts

Jejunum

Caecum

Duplication

Part of ileum

Appendix

Septa

ascending colon part of transverse colon 

 

At month 3 herniated midgut returns to abdo cavity.  Comparative reduction in size of liver to growth  Expansion of abdo cavity. Cephalic part fixes to lef Caudal swelling descends from under liver to right iliac region.

Hindgut o

o

Hindgut  Defined as 2/3 along transverse colon in adult.  Inferior mesenteric artery All arteries reach gut via dorsal mesentery.  Dorsal mesentery derived from visceral layer of lateral plate mesoderm. Hindgut endoderm

Distal 1/3 of transverse colon

Descending colon

Sigmoid colon

Hirshsprung's Disease (aganglionic megacolon)

Rectum

Rectal atresia

Imperforate anus

Rectal fistulae

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Cloaca is a expanded area of hindgut

Upper anal canal

Lining of urinary bladder and urethra

Inner endoderm Outer is ectoderm  Outer depression of ectoderm is anal pit Allantois separated from terminal hindgut by ridge of mesoderm = urorectal septum o Anterior allantois forms urogenital sinus o Posterior allantois forms anorectal canal. @ 7 wks urorectal septum reaches cloacal membrane and fuses. Fusion forms perineal body. Cloacal membrane becomes urogenital membrane and anal membrane posteriorly. o o

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How is the liver supported?   

Falciform ligament Triangular ligaments Coronary ligaments

Name two ligaments associated with the spleen?  

Lienorenal ligament o Peritoneal fold Gastrosplenic ligament o Peritoneal fold

Name the five arteries that supply the stomach?     

Lef gastric (LO and lesser curve) Short gastrics (fundus) + lef gastroepiploic (greater curvature)  Splenic artery Right gastric  HEPATIC ARTERY Gastroduodenal  Common hepatic artery Right gastroepiploic (greater curve)  gastroduodenal  CHA.

Give the blood supply of the pancreas 

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Blood supply o splenic artery runs along the top margin of the pancreas, and supplies  neck,  body  tail of the pancreas. Superior pancreaticoduodenal  Coeliac trunk Inferior pancreaticoduodenal  Superior mesenteric

Name the main branches of the superior mesenteric artery 1. 2. 3. 4. 5.

Inferior pancreaticoduodenal Middle colic Intestinal branches (jegunal and ileal) Right colic Ileocolic

Where does the inferior mesenteric arise? Supplies?  

L3 from abdo aorta. Gives rise to: o Lef colic artery o Sigmoid branches o Superior rectal

Appendicitis pain?   

Slow onset umbilical pain  pain is reffered to T10 dermatome around umbilicus Inflammation of midgut overlying parietal peritoneum supplied with somatic nerves then leads to colicky pain in the right iliac fossa – pts writhe around. Rebound pain due to localised peritonitis.

Lymphatic drainage of the abdominal wall? Above the umbilicus, lymph drains to the pectoral group of axillary nodes. Below the umbilicus, lymph drains to the superficial inguinal nodes.

What structure does the median umbilical ligament represent? Obliterated umbilical vein.

What structures form the posterior wall of the inguinal canal? 

Posteriorly = conjoint tendon + transversalis fascia

What incision for open appendectomy? The McBurney incision for appendicectomy. Would cut through external oblique, internal oblique and transversus abdominis. They are located laterally in the abdominal wall, stacked upon one another.

How would you treat a neonate umbilical hernia? An umbilical hernia is relatively common in neonates, particularly in premature births. There is usually herniation of small bowel, but the neck of the hernia is wide and strangulation is rare. They ofen close spontaneously in the first few years.

What is the nerve supply of the conjoint tendon? The conjoint tendon is supplied by the ilioinguinal nerve (L1)

What is a caput medusa? Porto-systemic anastomoses via opening of umbilical veins around umbilicus.  Connection between: o Portal  veins in ligamentum teres and superior o Systemic  Superior/Inferior epigastric veins.

Portal venous system- name the constituent parts 

Contains: o Portal vein o Splenic vein o Superior and inferior mesenteric veins  (to absorb all the nutrients from GI tract and do first pass metabolism).

What is adrenal medulla nerve supply? 

Symp o o

o

The adrenal medulla is the only structure that receives preganglionic sympathetic fibres. These arise largely from T10, pass with the splanchnic nerves, and then via the coeliac plexus to the adrenal medulla, whose cells are effectively postganglionic neurones. However, adrenaline is released as a hormone rather than a neurotransmitter close to the effector organ.

Define the transpyloric plane              

L1 or half way between pubic symphysis and suprasternal notch. Spleen Pylorus Lef colic flexure Right colic flexure Transverse colon Origin of portal vein End of spinal cord End part of duodenum Fundus (gallbladder) Origin of sup. Mes. Artery. Renal hila DJ flexure Neck of pancreas

Attachments of the external obliques  

ASIS Pubic tubercle

Where is the linea semilunaris?

Name the structure producing the lateral umbilical fold. The lateral umbilical fold (contains the inferior epigastric artery)

Study the inguinal canal Name the structures forming the roof, floor, posterior and anterior walls of the inguinal canal Anterior wall = external oblique Roof = Internal obturator + transversus abdominis Floor = Inguinal ligament + lacunar ligament Posterior wall = conjoint tendon and transversalis fascia

Name the nerve which lies over the spermatic cord or round ligament in the inguinal canal? Ilioinguinal nerve (L1)

What is the main function of the iliotibial tract? IT tract is a lateral thickening – a continuation of the proximal part of gluteus maximus.  It supports the knee o In addition, the ITB contributes to lateral knee stabilization. o When gluteus maximus is contracted it supports the extended knee (locking it)  Tensor fasciae latae also acts on the IT tract to provide stability to the hip and the knee in the upright posture (Superior Gluteal Nerve).

Which direction does the patella/knee dislocate in normally? 

Patella has a tendency to dislocate laterally o Described by Q angle. o Tendency to allow patella to be pulled laterally and upwards. o Vastus medialis inserts on medial side of patella to PULL BACK PATELLA in a medial opposing direction. o Strong medial retinacular fibres. o Lateral protuberance condyle – protrudes anteriorly more than medial therefore helps hinder dislocation.

Describe the mechanism of the physiological knee locking and unlocking Locking Full extension  Taut anterior cruciate (ACL)  No further symmetrical extension  Medial femoral condyle moves back – lateral condule moves forwards  results in Femur internally rotates on tibia on axis of ACL  Medial/lateral collateral ligaments tighten maximally  At this pt TFL and GM tighten the IT tract  Knee is hyper extended therefore locked. Unlocking Popliteus externally rotates femur on tibia  locked ligaments loosen  hamstrings can then flex the knee.

Draw a dermatome map for lower limb

Name the cutaneous nerves supplying the foot

Peroneal = common fibular

Name the areas drained by the 3 groups of superficial inguinal lymph nodes The superficial inguinal lymph nodes are the inguinal lymph nodes that form a chain immediately below the inguinal ligament.  Found in femoral triangle  Approximately 10 of them  Receive afferent lymph from o Scrotum o Perineum o Buttock o Abdo wall below the umbilicus o Vulva o Anus (below pectinate line) o The thigh and medial side of the leg.  (THE LATERAL LEG DRAINS TO POPLITEAL FOSSA LYMPH NODES).

Understanding the Sub-talar joint (list the evertors and invertors)   

Inversion and eversion of the foot OCCURS at the subtalar joint. It is a composite of the posterior talcalcaneal and talocalacaneonavicular joints – functioning as one joint. The muscles which act on the joint are: o The lateral compartment of the leg muscles (fib long and brevis) provide eversion of the foot  Sole of the foot attempts to face outwards. o The anterior compartment of the leg’s tibialis anterior provides inversion at the subtalar joint. (Tib ant. Provides dorsiflexion and inversion)  Inversion is movement of sole inwards to face each other – it occurs at the subtalar joint).

Look up the details of the cruciate and trochanteric anastomoses? 

The cruciate anastomosis is a circulatory anastomosis in the upper thigh of the inferior gluteal artery, the lateral and medial circumflex femoral arteries, and the first perforating artery of the profunda femoris artery. Also, the anastomotic branch of the posterior branch of the obturator artery. The cruciate anastomosis is clinically relevant because if there is a blockage between the femoral artery and external iliac artery, blood can reach the popliteal artery by means of the anastomosis.

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The trochanteric anastomosis provides circulation around the head of the femur. It includes the superior gluteal artery and the medial and lateral circumflex femoral arteries (the former of which provides the main supply to the femur). o Due to artery of the head of the femur degrading with age to become ligamentum teres.

Name the four structures in the subsartorial (adductor) canal    

Femoral artery Femoral vein Saphenous nerve (the largest cutaneous branch of the femoral nerve (L2,L3,L4) – strictly sensory. (L3,L4) Nerve to vastus medialis (a branch of the femoral nerve)

Why is the iliofemoral ligament particularly important? 

Iliofemoral ligament o Connects Ilium (hip bone) to femur o Most important (STRONGEST + PREVENTS HYPEREXTENTION OF HIP) ligament out of the 3 (iliofemoral, ischiofemoral, pubofemoral) o Shaped like Y with stems from:  ASIS  Acetabular rim o Attaches to:  Upper and lower end of intertrochanteric line.

Different types of ankle injury  

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Twisted ankles  ofen tear of anterior talofibular band of LATERAL LIGAMENT o Results in chronic pain and instability. Ankle fractures o Ofen come with medial and lateral collateral ligament damage as will as distral tibiofibular ligaments o Simply dealing with bony injury yields poor outcomes. Maisonneuve fracture o A tear along interosseous membrane along with medial ligament rupture PLUS fracture of proximal shaf of fibula.

Nerve supply of biceps femoris? Dually innervated  Long head = tibial portion of sciatic nerve.  Short head = common fibular nerve.

Describe ligaments of knee 

Knee

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LCL, ACL, PCL, MCL injury. “PM and AL” mnemonic o AL means ACL arises from plateau and passes laterally inserting on medial side of lateral condyle o PCL arises way back on plateau and passes medially – inserting lateral aspect of medial femoral condyle far down posterior. GREAT Mnemonic to remember strucutres anterior  posterior

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“MALLMP” on plateau

What is the unhappy triad? 

Occurs when there is a blow to lateral side of knee when foot planted on ground. o Main problem medially  1st = MCL tear  2nd = medial meniscus tear  3rd = ACL tears as taught during extension

Why are perforating veins between deep and superficial veins in lower limb important? Perforating veins are communicating vessels between the superficial and deep veins. Valves in the veins ensure one-way flow of blood from superficial to deep veins, and then back to the heart. This is important as muscle pump of the deep veins is used to pump deoxygenated blood back to the heart for recirculation. IN the arm the superficial veins pump blood back to the heart while in the leg the perforating veins direct the blood towards the deep veins, so that the soleus muscle can act as a pump to return the blood to the heart.

Give two clinical important facts about the soleal plexus of veins? 

Important muscle pump for pumping blood back to heart.

Lymphatic route from melanoma of right hallux Dorsum of foot and anterior of leg and thigh run superficially follow course of great saphenous vein ending in superficial inguinal nodes  drain through saphenous opening  deep inguinal nodes  through femoral canal  enter abdomen  some drains in Cloquet’s node (in inguinal region, considered the superiormost deep inguinal node), rest drains to internal and external pelvic nodes

Lymphatics from sole of foot and posterior leg runs superficially with short saphenous vein to popliteal lymph nodes  then follow deep veins to deep inguinal nodes lying in femoral triangle.

Give two functions of flexor pollicis longus Flexor of wrist when thumb fixed Flexor of thumb joint.

Describe the basic embryology of limb development  Forelimbs begin formation first at the 4th week initiated by Tbx5  Followed by hind limbs  They arise at PRECISE POSITIONS Limb development   Week 5 o Limb buds form   week 6 o Grow out   week 8 o Structural definitions arise. o Based on proximal/distal patterning  Humerus specified first then radius/ulnar then digits.

Limb outgrowth and patterning Limbs begins lateral protrusions of mesenchyme (mesenchyme = loose embryonic mesoderm tissue that develops into connective skeletal tissues such as bone and lymph) with ectoderm surrounding it. 

The tip of limb is the APICAL ECTODERMAL RIDGE (AER) o AER produces a signal that promotes proximal/distal development of limb. o Removal of AER leads to truncation of limb. o Secretes important factors:  FGF8 expressed in AER.  FGF8 is the molecule responsible.  The length of time cells are exposed to FGF8 indicates distal/proximal location.  Cells close to source of FGF8 remain undifferentiated.  Those out of reach of FGF8 signal start to differentiate Failures in AER  Thalidomide in 1st trimester results in lost of proximal limb structures – it inhibits cell growth/ encourages cell death. (FGF8 still expressed so only distal structures made.  Perturbs distal “progress zone”. Dorsal/palmar patterning is controlled by the ectoderm. (Wnt7a)  Ectoderm! produces signals that confer dorsal/palmar information.  Wnt7a secreted protein is produced in dorsal part of lumb only o Wnt7a diffuses from ectoderm into mesoderm where it induces expression of genes for dorsal things. Zone of Polarising activity (ZPA) produces SHH and therefore cranial/caudal patterning Cranial caudal (thumb to little digit) patterning depends on SHH.  SHH (sonic hedgehog protein)  Gradient of SHH formed and structures specified based on the conc gradient. Hox genes controlled by [SHH]

Summary Hox genes directed theref...