Gastrointestinal Tract Development PDF

Development of gastrointestinal tract Part 1 of 3 Dr. Katie Dixon Discipline of Anatomy & Histology [email protected]  Learning Objectives 1) Outline main features and events in early development of GIT. 2) Describe how three-dim...

Development of gastrointestinal tract Part 1 of 3 Dr. Katie Dixon Discipline of Anatomy & Histology [email protected]  Learning Objectives 1) Outline main features and events in early development of GIT. 2) Describe how three-dimensional body is formed from 2-dimensional disc of embryonic tissue which forms on yolk sac. 3) Outline process of GIT formation, tracing first formation of GIT, followed successively by major divisions of GIT and then development of its major vessels and accessory organs. 4) Outline processes that result in major congenital abnormalities of GIT: o Herniation and abnormalities of rotation of midgut, o Umbilical hernia o Congenital omphalocele and gastroschisis o Meckel's diverticulum o Congenital megacolon - Hirschsprung's disease.  Outline of video 1) Disc to tube, folding of embryo. 2) The early locations of fore-, mid- and hindgut, and their arterial supply 3) Mesenteries 4) Foregut: growth, derivatives, abnormalities 5) Midgut: growth, derivatives, abnormalities 6) Hindgut: growth, derivatives, abnormalities Overview: GIT development Foregut o Oral cavity o Oesophagus o Stomach o ½ Duodenum o liver, gall bladder o pancreas Midgut o ½ Duodenum o jejunum, ileum, caecum o ascending colon o 1/2 transverse colon Hindgut o 1/2 transverse colon o Descending colon o Sigmoid colon o Rectum o superior part of anal canal  A 3-layered disc ect mes end embryonic dis ectoderm o this is where it all begins mesoderm endoderm ▪ by third week embryo is flat 3 layer disc and it has ectoderm, mesoderm and endoderm innermost layer Trilaminar disk 3 layered embryonic disc 3rd week Schoenwolf et al. Larsen’s Human Embryology © 2008 Churchill Livingstone  Early primordia mesoderm from lateral plate o if it take plane of section through, it results with this picture on right that shows lateral layer of mesoderm o gastrointestinal system develops from endoderm and lateral plate mesoderm 14 days  Early primordia with further growth lateral plate mesoderm starts to hollow out o as result of this hollowing out of lateral plate mesoderm it divides into somatic and splanchnic neck components ▪ it's splanchnic neck component that goes on to become most primitive lining of gastrointestinal tract 16 days  Formation of gut tube then gut tube is formed it's created during fourth week how is gut tube formed from flat disc? o The main force is differential growth rates of different portions of embryo 1. The embryonic disc grows faster in length than yolk sac. 2. The expanding embryonic disc bulges and forms into convex shape. 3. As result of this folding, cranial (head), lateral, and caudal (tail) edges of embryonic disc are brought together along ventral midline. From; Developing Human, Moore Persaud Saunders  Formation of gut tube as that trilaminar disk folds into cylinder, it results with tube consisting of foregut extending into head region, midgut in wide communication with yolk sac and hindgut extending into tail o this middle picture is plane of section through midgut o far right picture is plane of section through midgut to hindgut ▪ in this picture over gut tube suspended by both dorsal and ventral mesentery and flanked on either side by coelomic cavity ▪ lateral plate mesoderm lining these cavities, differentiates into simple squamous epithelium of peritoneum coelomic cavity Hindgut 18 days Midgut  Formation of gut tube by end of first month, organ buds start to grow out from gut tube o bulge for stomach and beginnings of pancreas and liver are shown on the left end picture in first plane of section, that organs are supported by both dorsal and ventral mesentery but in far right picture over through midgut, ventral mesentery of midgut and hindgut disappears but dorsal mesentery remains Foregut Midgut 1 month  Folding summary Midline fusion transforms flat embryonic endoderm into gut tube. o it go from three-layer disc to gut tube When edges of ectoderm fuse along ventral midline, space formed within lateral plate mesoderm is enclosed in embryo and becomes intraembryonic coelom. Initially, gut consists of foregut and hindgut, separated by future midgut, which remains open to yolk sac. o it get 3 distinct parts of gut tube As lateral edges of various embryonic disc layers continue to join together along ventral midline, midgut is progressively converted into tube, and yolk sac neck correspondingly is reduced to slender vitelline duct. o midgut is eventually converted into tube and yolk sack into slender duct  Folding video https://www.youtube.com/watch?v=yXUv4MPuNTA  Folding video https://www.youtube.com/watch?v=yXUv4MPuNTA during fourth week of development period of rapid growth, embryo begins to change shape from flat trilaminar disc into cylinder o process known as embryonic folding  Folding video https://www.youtube.com/watch?v=yXUv4MPuNTA embryonic folding occurs in 2 planes and is result of differing rates of growth of embryonic structures o horizontal plane & median plane  Folding video https://www.youtube.com/watch?v=yXUv4MPuNTA folding of embryo in horizontal plane results in development of 2 lateral body folds  Folding video https://www.youtube.com/watch?v=yXUv4MPuNTA folding in median plane results in development of cranial and caudal folds  Folding video https://www.youtube.com/watch?v=yXUv4MPuNTA folding in both of these planes takes place simultaneously, resulting in rapid development of embryo  Folding video https://www.youtube.com/watch?v=yXUv4MPuNTA cylinder consists of 3 layers derived from trilaminar embryonic dis o ectoderm outermost layer  Folding video https://www.youtube.com/watch?v=yXUv4MPuNTA cylinder consists of 3 layers derived from trilaminar embryonic dis o mesoderm located in between  Folding video https://www.youtube.com/watch?v=yXUv4MPuNTA cylinder consists of 3 layers derived from trilaminar embryonic dis o endoderm innermost layer  Folding video https://www.youtube.com/watch?v=yXUv4MPuNTA endoderm of trilaminar disc is mainly responsible for formation of gastrointestinal tract  Folding video https://www.youtube.com/watch?v=yXUv4MPuNTA As embryonic folding continues endoderm moves towards midline and fuses, incorporating dorsal part of yolk sac to create primitive gut tube  Folding video https://www.youtube.com/watch?v=yXUv4MPuNTA midgut hindgut foregut Primitive gut tube differentiates into 3 main parts foregut, midgut and hindgut  Folding video https://www.youtube.com/watch?v=yXUv4MPuNTA foregut can be seen at cranial or head end of embryo  Folding video https://www.youtube.com/watch?v=yXUv4MPuNTA it is temporarily closed by oropharyngeal membrane which at end of fourth week of development ruptures to form mouth  Folding video https://www.youtube.com/watch?v=yXUv4MPuNTA midgut lies between foregut and hindgut and remains connected to yolk sac until fifth week of development  Folding video https://www.youtube.com/watch?v=yXUv4MPuNTA As embryonic folding continues, connection to yolk sac narrows into to stock known as vitellin duct  Folding video https://www.youtube.com/watch?v=yXUv4MPuNTA hindgut lies at caudal or tail end of embryo  Folding video https://www.youtube.com/watch?v=yXUv4MPuNTA it is temporarily closed by cloacal membrane which during seventh week of development ruptures to form urogenital and anal openings  Folding video https://www.youtube.com/watch?v=yXUv4MPuNTA as result of embryonic folding, major body plan is established and 3 germ layers continue to differentiate, giving rise to their own specific tissues and organ systems  3 regions of gut tube 4.5mm Foregut Midgut Hindgut Professor Alfred Cuschieri, http://staff.um.edu.mt/acus1/Gastro-intestinal.pdf  3 regions of gut tube gut tube is present by week 4 o there are 3 main regions: foregut, midgut and hindgut ▪ all have different arterial Supply and give rise to different organs 1. foregut consists of pharynx, Thoracic oesophagus and abdominal foregut ▪ abdominal foregut forms abdominal oesophagus, stomach and about half of duodenum and it also gives rise to liver, gallbladder, pancreas and their Associated ducts 2. midgut forms other half of duodenum, jejunum and ileum, ascending colon and about 2/3 of transverse colon 3. hindgut forms other third of transverse colon, descending colon, sigmoid colon and upper 2/3 of anorectal canal ▪ lower third of anorectal canal is NOT from gut tube  Regions distinguished based on arterial supply by convention gut region, boundaries are distinguished on basis of their arterial Supply o 5 aortic branches → Thoracic part of foregut (pharynx and thoracic oesophagus) o Coeliac artery → Abdominal foregut … abdominal oesophagus, stomach, Superior half of duodenum and its derivatives including liver, gallbladder and pancreas o Superior mesenteric artery → Midgut… o Inferior mesenteric artery → Hindgut… 5 definative aortic supply thoracic part of foregut n  Mesentery what holds it all in place? o mesentery is fold of tissue that attaches organs to body wall ▪ End of 4th week almost entire gut tube suspended from posterior abdominal wall in peritoneal cavity by double fold of mesoderm – dorsal mesentery Ventral mesentery has disappeared from level of midgut that exists for terminal part of oesophagus, stomach and part of duodenum. ✓ From this picture, abdominal oesophagus (stomach and Superior part of duodenum) are all suspended by both ventral and dorsal mesentery but rest of abdominal gut tube excluding rectum is suspended in abdominal cavity by dorsal mesentery only so ventral mesentery of midgut and hindgut  Intraperitoneal, retroperitoneal and secondarily retroperitoneal organs of abdominal GIT organs of GIT can be classified according to how they sit within abdominal cavity o Intraperitoneal- organs suspended within peritoneal cavity by mesentery ▪ Liver, stomach, sigmoid colon, jejunum, ileum o Retroperitoneal- organs embedded in body wall and covered by peritoneum ▪ Bladder (anterior), Kidneys (posterior) o Secondarily Retroperitoneal- initially suspended but both mesentery and organ fuse with body wall ▪ suspending some Intraperitoneal organs disappears as both mesentery and organ fuse Schoenwolf et al. Larsen’s Human Embryology © 2008 Churchill Livingstone with body wall  Development of gastrointestinal tract Part 2 of 3 Dr. Katie Dixon Discipline of Anatomy & Histology  The foregut derivatives oesophagus stomach proximal part of duodenum liver, gall bladder pancreas  Oesophagus Develops from foregut immediately caudal to pharynx Partitioning of trachea from oesophagus by tracheoesophageal septum o it then get development of septum to separate trachea from oesophagus so this is called tracheoesophageal septum Oesophagus is initially short, elongates rapidly due to growth and descent of heart & lungs Reaches final relative length by 7th week o it assumes postnatal proportions in relation to location of stomach  Oesophagus Epithelium proliferates and partially obliterates lumen but recanalization occurs by end of embryonic period o its epithelium changes during development ▪ it starts out as stratified columnar epithelium and it proliferates until it partially obliterates lumen and then it opens up around about week 8 but with multi-layered ciliated epithelium and that eventually becomes stratified squamous epithelium by fourth month ▪ that process is called recanalization  Oesophagus – Developmental abnormalities a. Oesophageal atresia o Blockage of oesophagus resulting from deviation of tracheoesophageal septum in posterior direction >>> results in incomplete separation of oesophagus from laryngotracheal tube. o Results in: i. newborns appear to be quite healthy and first fuse follows normal but then suddenly fluid returns through nose and mouth and respiratory distress occurs ii. inability to pass catheter through oesophagus into stomach would strongly suggest esophageal atresia iii. Foetus unable to swallow amniotic fluid >>> lead to polyhydramnios Polyhydramnios = excessive accumulation of amounts of amniotic fluid o 1 in 3000-4500 live births (1/3 of those which are born prematurely) o Treatment: Surgical repair with success rate of about 85%  Oesophagus – Developmental abnormalities b. Oesophageal stenosis o Narrowing of lumen, usually in distal third ▪ Usually from incomplete recanalization during 8th week recanalization is process where epithelial lining is supposed to change but it could also occur for such as from failure of oesophagus or blood vessels to develop which would lead to atrophy c. Short oesophagus o caused by failure to elongate as neck & thorax develop >>> congenital hiatal hernia ▪ this could lead to top part of stomach herniating into oesophagus  The stomach: rotation A. 27 days B. 28 days C. 35 days  The stomach: rotation A. 4th week- stomach first becomes apparent o stomach is suspended by both dorsal and ventral mesentery ▪ NOTE: ventral mesentery that connects it to body wall o during fourth week it begin to get small dilation on gut tube where stomach is going to form and that forms enlarged lumen in tube o when stomach first appears its concave border faces dorsally B. 5th week- dorsal wall grows faster than ventral wall o it soon enlarges and broadens ventrodorsally o resulting in greater and lesser curvature ▪ during next 2 weeks dorsal border of stomach grows faster than its ventral border and this demarcates greater curvature of stomach 2 positional shifts bring stomach to its adult configuration a. C. 35 days = Stomach rotates undergoes 90 degree rotation, resulting in greater curvature lies to left ▪ first is 90° rotation in clockwise direction around its longitudinal axis so that its originally dorsal convex border faces left and its ventral convex border faces right b. D. 56 days = Also rotates slightly around ventrodorsal axis so that greater curvature faces slightly caudally and lesser curvature slightly cranially ▪ Second positional shift can consists of minor tipping of pyloric end of stomach in cranial direction so that long axis of stomach is positioned diagonally across body  Stomach - Developmental abnormalities Pyloric stenosis The lower portion of stomach that connects to small intestine is known as pylorus (distal sphincteric region) In pyloric stenosis, muscles in this part of stomach enlarge, narrowing opening of pylorus and eventually preventing food from moving from stomach to intestine. o it get enlargement of muscles in this part of stomach so this Narrows opening of pylorus and can prevent food from moving through to intestines Affects babies between 2 and 8 weeks of age o Causing Stomach distention, highly forceful projectile vomiting >>> can highly rapidly lead to dehydration. ▪ babies generally have weight loss or poor weight gain 1/150 males (more common) o Exact cause unknown but highly prevalent in 1/750 females monozygotic twins >> genetic factors? ▪ its exact cause is NOT highly known but it is more common in Twins and it's more common if parent has had condition so there's some genetic factor involved Treatment: repaired surgically  Dorsal & ventral mesenteries The liver and spleen develop within mesenteries of stomach o ventral body wall also encloses developing liver o spleen also develops within mesentery of stomach  Liver & Gall bladder Proximal duodenum “buds” 4 weeks 5 weeks these pictures show development of those organs at 4 weeks and at 5 weeks so this shows how quickly factors change with rapid duodenal growth Liver bud sprouts first from duodenal endoderm o On day 22 small endodermal thickening –the hepatic plate Moore & Persaud. Developing Human © 2003  Liver & Gall bladder Proximal duodenum “buds” 6 weeks 5 weeks it have ventral pancreatic bud and dorsal pancreatic bud o these will eventually fuse to form pancreas 26 day endodermal thickening (cystic diverticulum) on ventral side of duodenum caudal to base of hepatic diverticulum will form gall bladder and cystic duct. entrance of bile duct into duodenum gradually shifts from its initial position into posterior one so this explains why bile duct in adult passes posterior to duodenum and head of pancreas o cells at junction of hepatic and cystic duct proliferate to form common bile duct  Liver & Gall bladder Proximal duodenum “buds” 20 days 22 days 26 days 32 days hepatic bile bud duct hepatic duct liver cystic gall bud bladder Ventral Dorsal Ventral Dorsal pancreatic pancreatic pancreatic pancreatic bud bud bud bud duodenum starts developing in early in fourth week o it grows rapidly and it forms C shape o liver, gallbladder and pancreas develop from buds ▪ liver forms from hepatic bud ▪ gallbladder from cystic bud ▪ pancreas forms from ventral and dorsal pancreatic buds on Day 26, dorsal pancreatic Bud grows into dorsal mesentery opposite hepatic duct diverticulum  Pancreas 26 days bile hepatic duct bud liver cystic gall bud bladder ventral dorsal Ventral Dorsal pancreatic pancreatic pancreatic pancreatic bud bud bud bud by day 32 ventral pancreatic bud connects to common bile duct  Pancreas 5th week: ventral pancreatic bud with mouth of common bile duct migrates around posterior side of duodenum o then during fifth week ventral pancreatic bud migrates around posterior side of duodenum and meet dorsal pancreatic bud …forms through rotation  Pancreas Week 6: pancreatic buds fused to form definitive pancreas o by week 6, both ventral and dorsal pancreatic buds fuse to form pancreas o main duct of ventral Bud ultimately becomes major major pancreatic duct pancreatic which drains entire duct pancreas  Pancreas - Developmental abnormalities Annular pancreas (ring-shaped pancreas) Arises when 2 lobes of ventral pancreatic bud (a normal variation; that can be called bifid or bilobed ventral pancreatic bud) migrate in opposite directions around duodenum to fuse with dorsal pancreatic bud >>> then compress duodenum >>> may cause gastrointestinal obstruction → duodenal stenosis 1 in 12,000 newborns Treatment: by-passing obstructed segment Schoenwolf et al. Larsen’s Human Embryology © 2008 Churchill Livingstone  Development of gastrointestinal tract Part 3 of 3 Dr. Katie Dixon Discipline of Anatomy & Histology  The midgut derivatives distal duodenum jejunum, ileum, cecum ascending colon, 2/3 of transverse colon  Physiological umbilical herniation during fifth week ileum elongates rapidly and it's thrown into this hair pin fold called primary intestinal Loop (U-shaped loop of gut) o that it grows too fast for space available ▪ Not enough room in abdomen for rapidly growing midgut o also to add to space constraints liver and kidneys are already there and they've taken up lot of room o this continued gut elongation and pressure from growth of other organs forces this primary intestinal loop to herniate through umbilicus where it continues to grow ▪ this is known as normal herniation so physiological umbilical herniation ▪ it needs to happen for proper midgut development  Rotation of midgut as it herniates primary intestinal Loop rotate rotates 90° in counterclockwise around axis of superior mesenteric artery in umbilicus Occurs Week 6-8, and rotation completed by 8th week o small intestine elongates to form jejunoileal loops and caecum and appendix grow  Return of midgut to abdomen Week 10-12: intestinal loop retracts into abdominal cavity - rotates further 180 degrees counterclockwise (thus, total 270 degrees = normal GIT positioning) o there's more room inside so primary intestinal Loop returns to abdominal cavity rotating additional 180° counterclockwise so net rotation is 270° counterclockwise ▪ during 11th week retracting midgut completes this rotation as caecum is positioned inferior to liver ▪ caecum is then displaced inferiorly pulling down proximal hindgut to form ascending colon ▪ descending colon is simultaneously fixed on left side of posterior abdominal wall ▪ jejunum, ilium, transverse colon, sigmoid colon remain suspended by mesentery Schoenwolf et al. Larsen’s Human Embryology, 4th ed. © 2008  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY rotation of midgut happens during second month of uterine life  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY this is gastrointestinal tract consisting of foregut, hindgut and midgut  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY midgut is continuous with vitelline duct or Yolk stalk which later becomes obliterated  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY here's aorta  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY Coeliac trunk for foregut, inferior mesenteric artery for hindgut and superior mesenteric artery for midgut  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY as midgut develops, it protrudes into body's stalk, forming loop with superior mesenteric artery, forming axis of loop  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY as it protrudes, midgut loop makes quarter turn counterclockwise, so its distal part is to left and its proximal part is to right  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY distal part of loop develops bulge that will become caecum  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY proximal part of loop becomes quite convoluted  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY during time these changes are happening, body continues to grow and abdominal cavity becomes large enough to allow midgut to return  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY proximal part of loop returns first  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY it passes under distal part and over to left, that's towards us in this view  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY distal part of loop returns last  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY it passes in front of proximal part and results over to right  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY let's look at same sequence of events from in front and to left so that it can understand how these changes produce rotation of midgut  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY here's midgut loop protruding towards  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY making its first quarter turn counterclockwise  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY bulge appears for caecum  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY and proximal part of loop becomes convoluted  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY abdomen becomes larger and proximal limb of loop returns it passes under distal limb and in effect making another quarter turn counterclockwise  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY abdomen becomes larger and proximal limb of loop returns it passes under distal limb and in effect making another quarter turn counterclockwise  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY then distal limb returns, completing third quarter turn  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY this proximal part of midgut distal duodenum results behind this distal part of midgut, proximal transverse colon  Rotation of midgut https://www.youtube.com/watch?v=AscKR_cQExY Developmental abnormalities of physiological herniation and rotation of midgut it's quite easy to imagine with all of these rotations that factors can easily go wrong and they do so these abnormalities or malrotations result in number of different symptoms: a. Acute abdominal pain b. Vomiting c. Gastrointestinal bleeding d. Failure to thrive e. Occasionally remain clinically silent Diagnosis: barium swallow or barium enema in conjunction with X-rays Treatment: treated surgically  Developmental abnormalities Non-rotation of midgut: “left-sided colon” 1st 90o rotation OK o jejunum & ileum on right but 2nd 180o fails o Whole colons are on left hence ‘left sided colon’ → generally asymptomatic  Developmental abnormalities Reversed rotation of midgut normal 1st 90o rotation OK o jejunum & ileum on right but 2nd 180o CLOCKWISE o = net 90o clockwise rotation o rotation happens in opposite direction so that should also be counterclockwise rotation but in this case it's clockwise rotation so that leaves everything about 90° out of whack ▪ this results in duodenum and transverse colon each lying on wrong side of superior mesenteric artery and this may cause obstruction to colon by pressure from artery duodenum ventral to transverse colon  Developmental abnormalities Volvulus of intestine volvulus refers to twisting of intestines General abnormal rotation & fixation of midgut o Volvulus may occur as suspended regions of gut twist around themselves → Constriction & obstruction of intestine and/or compromising its blood supply (cut off blood supply) → leading to: ▪ Intestinal ischemia (restriction in blood supply) may cause superior mesenteric artery to become constricted as well ▪ Infarction (tissue death (necrosis)) Schoenwolf et al. Larsen’s Human Embryology © 2008 Churchill Livingstone Developmental abnormalities Umbilical Hernia umbilical hernia is relatively common one o this happens when intestines herniate back through umbilicus after they've been returned to abdominal cavity ▪ Intestines return to abdominal cavity during 10th week and then herniate through imperfectly closed umbilicus. o mass is usually NOT bigger than 5 cm and it is coated in skin ▪ Protruding mass covered by subcutaneous tissue & skin ▪ Reaches max size 1 month after birth, 1-5cm. ▪ Protrudes when crying, straining or coughing Surgery NOT required unless it persists after 3- 5 years.  Developmental abnormalities Congenital omphalocele & Gastroschisis Omphalocele 1/3500 o Bowel does NOT fully retract after physiological herniation o Herniated bowel is contained within membranous sac (epithelium of umbilical cord) Gastroschisis 1/10,000 o Bowel herniates through opening in body wall typically to right of umbilical cord, and is NOT contained within membranous sac Schoenwolf et al. Larsen’s Human Embryology © 2008 Churchill Livingstone  Developmental abnormalities Meckel’s Diverticulum Vitelline duct connects fetal intestine to yolk sac o embryonic duct that connects fetal intestine to Yolk stalk or Vitelline duct that should be obliterated during development Vitelline duct  Developmental abnormalities Meckel’s Diverticulum Meckel’s Diverticulum results from failure of that Vitelline duct (embryonic obliteration of duct) that connects foetal intestine to yolk sac to regress, causing Congenital lesion o Meckel’s Diverticulum is finger-like projection of ilium ▪ Vitelline duct normally regresses between 5-8 weeks However, Persists as remnant in approximately 2% of population. Most have no symptoms o 15 to 35% develop symptoms (intestinal obstruction, bleeding, peritonitis) before age 10 ▪ Symptoms very similar to appendicitis. Diverticulum is usually found within 1m of ileocaecal valve and is usually less than 12 cm in length. Up to 60% contains ectopic pancreatic or gastric mucosa (therefore can ulcerate). http://www.surgical-tutor.org.uk/default-home.htm?tutorials/meckels.htm~right and www.merck.com/media/mmhe2/figures/fg275_1.gif; http://www.kanalen.org/foraldrar/img/v5.jpg  Hindgut derivatives Left 1/3 to 1/2 of transverse colon Descending colon and sigmoid colon Rectum and superior part of anal canal  Development of hindgut Cloaca: Chamber at caudal end of hindgut & allantois that divides in most mammals into urinary bladder, rectum and related organs/structures. o Cloaca eventually divides to form bladder and rectum o it becomes divided by Urorectal septum which is wedge of mesenchyme and this produces infolding of walls of cloaca until it finally get full partition forming Moore & Persaud. Developing Human © 2003  Urorectal septum Week 4-6: Urorectal folds grow toward each other and fuse, dividing cloaca into urogenital sinus and anorectal canal o cloacal membrane is at site where gut tube meets body wall o Urorectal septum which growing down in this direction and joins that cloacal membrane and divides cloacal membrane into anal and urogenital Anal atresia in newborn membrane ▪ that point where Ural septum intersects cloacal membrane is future side of perineum Developmental Abnormality: Anal atresia o anal membrane persists, no trace of anal opening  Anal canal (endoderm) (ectoderm) portal anal canal has 2 completely separate Origins o upper 2/3 are derived from hindgut or endoderm o inferior third is from ectoderm because they have those 2 separate Origins, they have different blood and nerve supplies o Anatomic drawing of communication between venous system and systemic circulation. ▪ Upper 2/3 supplied by branches of inferior mesenteric arteries and veins serving hindgut, superior rectal vein, portal circulation (to liver) ▪ Inferior 1/3 supplied by branches of internal iliac arteries and veins, middle  Innervation of GIT: Enteric nervous system GIT is supplied by Enteric nervous system and component of that is myenteric plexus o Myenteric plexus ▪ Regulates processes in GIT including peristalsis, blood flow, secretion, absorption, endocrine processes ▪ These nerve cells migrate along length of GI tract cranial to caudal in weeks 7 to 12, to populate entire length this system develops during weeks 7 to 12 of development extend from oesophagus to anus  Developmental abnormalities Congenital megacolon: Hirschsprung Disease 1:5000 it results from gene mutation in one of several genes (e.g. RET gene) one issue in development of GIT nerve Supply o Nerves within bowel that are responsible for its movement (myenteric plexus) are missing → No intrinsic nerve supply in terminal bowel ▪ in normal development cells would migrate from neural crest to form networks of nerves in wall of colon ▪ However, myenteric plexus and megacolon occurs when this migration fails Partial or total obstruction of large intestine because of absence of ganglia and has no nerve Supply o if it have absence of ganglia in distal colon, this leads to lack of peristalsis in segment distal to dilated part ▪ buildup of waste and no passing of stool and therefore potential for obstruction  Developmental abnormalities Congenital megacolon: Hirschsprung Disease Severity depends on length of "aganglionic bowel” Symptoms – abdominal distention and no meconium in 1st 48 hrs o Most often presents soon after birth, with newborn NOT passing their first stool (meconium). ▪ it should be consideration for any child that doesn't pass meconium within 24 to 48 hours of birth ▪ sometimes they're even vomiting matter o This leads to progressive abdominal distension. Treatment o “pull-through” operations where aganglionic portion of colon is removed, and normal colon pulled through and sewn to anus (Duhamel procedure). ▪ surgical procedure to fix this involves moving aganglionic portion of colon and connecting healthy portion to anus so it's called pull through procedure  Eye Dr. Saeed Shokri Ph.D. of Anatomical Sciences Lecturer in Biomedical Sciences [email protected]  Learning Outcomes 1) Identify orbit's shape and walls. 2) Describe different layers of eyeball. 3) Describe refractive media of eyeball. 4) Recognize extra-ocular muscles and their actions and innervations. 5) Describe vasculature of orbit. 6) Identify structure of eyelid. 7) Describe lacrimal apparatus.  Bones of Orbit supraorbital foramen Frontal Superior orbital Lesser wing Ethmoid fissure Greater wing Optic canal Lacrimal Zygomatic Palatine Maxilla Inferior orbital fissure Maxillary sinus infraorbital foramen Anterior View Lateral View Gilroy et al, 2020, Gilroy Atlas, 4th Edition, Thieme Medical Publisher Inc  Bones of Orbit in lateral view, orbit has pyramidal shape o as pyramid it has base which is directed in interiorly and Apex directed posteriorly o it also has 4 walls: ▪ Roof: Frontal bone & Lesser wing of sphenoid roof of orbit separates orbit from anterior cranial fossa ▪ Floor: Maxilla (mainly), Zygomatic (anteriorly) & Palatine (posteriorly) Floor is thinnest wall of orbit because there is space which is called maxillary sinus within Maxilla so it's so prone to get fractured ▪ Medial Wall: Maxilla, Lacrimal, Ethmoid, Sphenoid body ▪ Lateral Wall: Zygomatic & Greater wing of sphenoid this wall is thickest wall of orbit and it is so important because it is so prone to direct trauma it also separates orbit from this fossa which is called temporal fossa o base is outlined by orbital margin ▪ above and below it have supraorbital foramen and infraorbital foramen o Apex is within optic canal ▪ lateral to optic canal, there is fissure in between Lesser wing and greater wing of this sphenoid which is called Superior orbital fissure o there's another fissure which is in between floor and lateral well o all these foramina and fissures and canal allow vessels and nerves to enter or exit orbit Eyeball  Eyeball 3 layers of eyeball: 1. Fibrous layer (outer coat): sclera & cornea ▪ as their name suggests contains lots of collagen fibres sclera provides shape and resistance of eyeball and it also gives attachment to extraocular muscles ✓ it can see anterior half of sclera is visible as white of eye cornea is completely transparent and it's also completely avascular and it allows the light to pass through cornea ✓ it can see cornea which looks like glass and protrudes anteriorly 2. Vascular layer or Uvea (middle coat): choroid, ciliary body, & iris ▪ large posterior part is choroid which contains lots of vessels which supplies sclera and retina ▪ second part is ciliary body which contains some smooth muscles ▪ it can see iris as thin contractile diaphragm with aperture Central aperture which is called pupil it can see iris and pupil which is covered by cornea ✓ iris determines colour of eye and also has lot some smooth muscles which controls size of pupil according amount of light passing through pupil 3. Neural layer (inner coat): retina ▪ third layer is neural layer or inner coat which is called retina it has 2 parts optic part posteriorly and non-visual part anteriorly ✓ optic part is thick because it contains 2 layers: ❖ outer pigmented layer ❖ inner neural layer → neural layer contains lots of photoreceptors including rods and cones ✓ non-visual part is continuation of outer pigmented layer of optic retina and it's line the ciliary body and also Iris it can also see optic nerve which is cranial nerve 2 and carrying sensory information from retina to brain it can see is called optic disc this is where axons of ganglion cell leaving eyeball o lateral to optic disc there is depression which is called macula lutea  Refractive Media Posterior Anterior Segment Segment Gilroy et al, 2020, Gilroy Atlas, 4th Edition, Thieme Medical Publisher Inc Anterior Chamber Posterior Chamber  Refractive Media it see suspensor ligaments called zonular fibres connects lens to the ciliary body o ciliary body are under control of parasympathetic nerves ▪ parasympathetic stimulation causes ciliary muscle to contract then zonular fibres relax in absence of stretching, internal tension causes lens to become more spherical to refract, light for near vision vice versa for distant Vision o as people age, their lenses become harder and more flattened ▪ these changes gradually reduces focusing power of lenses condition known as presbyopia ▪ some people also experience loss of transparency or cloudiness of lens from area of opaqueness which is called cataracts anterior to lens is called anterior segment and posterior to lens is called posterior segment. o Anterior segment is divided by iris and pupil into 2 chambers (Anterior & Posterior Chambers). ▪ anterior chamber in between cornea and Iris ▪ posterior chamber in between iris and lens o anterior segment is filled with fluid which is called aqueous humor ▪ it is produced by ciliary processes and then it drains into scleral venous network ▪ aquous humor is transparent and it provide nutrients for avascular structures including lens and cornea o posterior segment is occupied by structure which is called vitreous body ▪ it's jelly like structure it fills ▪ it's transparent and it permits light to pass from lens to retina ▪ it also holds retina against choroid Refractive media: cornea, aqueous humor, lens & vitreous body. Movements of Extra-ocular Muscles Movements of Extra-ocular Muscles  Movements of Extra-ocular Muscles movements of eyeball occur as turning around 3 axis including vertical axis, transverse axis and AP axis o they are described according to direction of movement of pupil from its primary position or of superior pole of eyeball from its neutral position ▪ in this movie it can see Mandarin is eyeball and there is pupil and iris and stick is vertical axis and these fingers act as extraocular muscles when eye turning around this vertical axis, pupil moves toward mid line which is called adduction it moves away from mid line which is called abduction when eye is turning around horizontal axis or transverse axis, pupil moves upwards which is called elevation it moves downwards which is called depression when eye is turning around AP Axis or anteroposterior axis, superior pole of eyeball rotates internally so it is called internal rotation it rotates externally which is called external rotation or extorsion ✓ these rotational movements accommodate changes in tilt of head  Extra-Ocular Muscles of Orbit in these 2 pictures it can see extraocular muscles of orbit from anterior View and Superior view Anterior View Superior View Gilroy et al, 2020, Gilroy Atlas, 4th Edition, Thieme Medical Publisher Inc  Extra-Ocular Muscles of Orbit 4 rectus muscles o as their name suggests rectus means straight because 4 rectus muscles rising from apex of orbit and then they go forward straightly and they attach to eyeball o 4 rectus muscles are named for their individual positions relative to eyeball ▪ when superior rectus contract, it can do elevation when contract independently such as Superior rectus can do intorsion ▪ when inferior rectus contract, it can do depression when contract independently such as inferior rectus can do extortion ▪ when medial rectus and lateral rectus contract, it can do adduction and abduction respectively ▪ Superior rectus and inferior rectus muscles, they also have secondary or tertiary actions such as when they contract together they can help medial rectus to do adduction 2 oblique muscles o from superior view, superior oblique like recti muscle is arising from apex of orbit and then it's tendon passing through this pulley which is called trochlea then it's tendon passing underneath superior rectus and attaches eyeball quite far back ▪ when they contract Superior oblique can do intorsion ▪ when they contract independently such as Superior oblique that tendon of superior oblique attaches to posterior of eyeball so that when it contract it can pull posterior of eyeball anteriorly so it can do depression o inferior oblique is only muscle of extraocular muscles that is NOT rising from apex of orbit but it's coming from anteromedial part of floor of orbit then it's passing underneath inferior rectus and then it's go quite far back and attaches to eyeball next to lateral rectus ▪ when they contract inferior oblique can do extortion ▪ inferior oblique can do elevation o they have secondary or even tertiary actions such as when 2 oblique muscles contract together they can help lateral rectus to do abduction 1 Levator palpebrae superioris  Extra-Ocular Muscles of Orbit Inferior rectus Medial rectus Lateral rectus Superior rectus Vertical Axis Superior Oblique Inferior Oblique  Testing Actions of Muscles of Orbit if gaze is first directed laterally, line of gaze coincides with plane of superior rectus and inferior rectus, then superior rectus produces elevation only and inferior rectus produces depression only. o during physical examination, physician directs patient to follow his or her finger laterally to test lateral rectus and then superiorly and inferiorly to test and isolate function of superior rectus and inferior rectus if gaze is first directed medially, line of gaze is coincides with plane of inserting tendon of superior oblique and inferior oblique, then superior oblique produces depression and inferior oblique produces elevation only o during physical examination, physician directs patient to follow his or finger medially to test medial rectus and then superiorly and inferiorly to test and isolate function of inferior oblique and superior oblique Testing Actions of Muscles of Orbit  Nerves of Orbit CN V3 Memory device: LR6SO4AO3  Nerves of Orbit superior oblique which is innervated by cranial nerve 4 o it is coming from brainstem and it is called trochlear nerve o superior oblique tendon passing through this trochlear lateral rectus is innervated by cranial nerve 6 o it's coming from brainstem and it's called abducent nerve ▪ only action of lateral rectus is abduction rest of extraocular muscles are innervated by cranial nerve 3 which is coming from brainstem and it splits into 2 branches Superior branches and inferior branches and it is called the oculomotor nerve it can also see ciliary ganglion within orbit o it is cranial nerve 3 and it's called oculomotor nerve that carries presynaptic parasympathetic fibers to ciliary ganglion and then it make synapse with post-synaptic parasympathetic nerve ▪ it goes toward towards eye through short ciliary nerve and it innervated smooth muscles of ciliary body and iris in this picture it can also see trigeminal nerve o it's splits into 3 branches V1, V2 and V3 ▪ V1 or ophthalmic nerve enters to orbit through superior orbital fissure and it splits into 3 branches  Supratrochlear n. Supraorbital Ophthalmic Nerve (V1) n. Supraorbital Supratrochlear n. n. Lacrimal n. Nasocilliary Frontal n. n. Infraorbitral n. Anterior View Superior View in this picture it can see that roof of orbit has been removed and from superior view it can see 3 terminal branches of ophthalmic nerve from lateral to medial: lacrimal nerve, frontal nerve and Nasocilliary nerve o then frontal nerve it splits into 2 branches supraorbital and Supratrochlear from anterior view all these 3 terminal branches of ophthalmic nerve supply structures related to anterior orbit (e.g., lacrimal gland and eyelids), face, and scalp. o it's sensory nerve and it's carrying sensory information from this different places to brain  Arteries & Veins of Orbit Lateral View Superior View  Arteries & Veins of Orbit in this picture from superior view, it can see internal carotid artery, and it gives off to ophthalmic artery then it's traveling along optic nerve through optic canal to enter to orbit and it gives off 3 main branches from lateral to medial: lacrimal, supraorbital and Supratrochlear o 3 terminal branches of ophthalmic artery (lacrimal, supraorbital and supratrochlear) supply extra-ocular muscles, lacrimal gland and eyelids, face, and scalp. Central retinal artery, short and long posterior ciliary and anterior ciliary supply different layers of eyeball. o as its name suggest Central retinal artery pierces optic nerve and Supplies retina o it can also see long posterior ciliary artery and short posterior ciliary artery and anterior ciliary artery ▪ all these ciliary branches they provides blood to different layers of eyeball o from lateral view, it can see 2 ophthalmic veins, inferior ophthalmic vein and Superior ophthalmic vein ▪ they join together and they exit orbit through superior orbital fissure and drain into this cavernous sinus anteriorly ▪ they make anastomoses with facial vein point is that there is no valve within this vein so if there is infection or inflammation in face, it can convey freely into orbit and involve eyeball or even it can involve meninges into cranial fossa  Eyelids Bulbar conjunctiva Palpebral conjunctiva Inferior conjunctival fornex Sagittal section through anterior orbital cavity Bulbar conjunctiva  Eyelids eyelids are movable fold with upper eyelid and lower eyelid o eyelids are covered anteriorly by thin skin and internally by mucus membrane which is called palpebral conjunctiva ▪ palpebral conjunctiva reflects onto eyeball to be continuous with which is called bulbar conjunctiva palpebral conjunctiva at the bottom ▪ point of reflection is called fornex (there is superior conjunctival fornex and inferior conjunctival fornex) bulbar conjunctiva covers sclera (loosely attached to sclera) or “white” of eyeball. deep to skin, it can see extraocular muscles deep to muscle, it can see superior tarsus or inferior tarsus connective tissue o tarsus forms skeleton of eyelid and contains tarsal glands. there is band of fibrous connective tissue that attaches to orbital margin through orbital septum deep to tarsus, it have tarsal gland that produces lipid substance to moen and lubricates margin of upper and lower eyelid it can also see levator palpebrae superioris which attaches to superior tarsus deep to this it have smooth muscle which is called Superior Tarsal muscle which is under control of sympathetic nerve o when it are so excited it contracts to elevate upper eyelid more Lacrimal Apparatus from anterior view it can see lacrimal gland o this gland is located in superior lateral part of orbit Production of lacrimal fluid is stimulated by parasympathetic impulses from CN VII (Facial nerve). 1. after producing, tears releases into conjunctival sac 2. then it crosses cornea from lateral to medial 3. accumulates in medial angle of eye which is called lacrimal Lake 4. then it drains into this lacrimal sack through this canaliculi (small canal) 5. then it passes through nasal lacrimal duct into nasal cavity in this space which is called inferonasal meatus  Anatomy of Ear Dr. Saeed Shokri Ph.D. of Anatomical Sciences Lecturer in Biomedical Sciences [email protected]  Learning Outcomes 1) Recognize different parts of ear including external, middle, and internal. 2) Describe auricle and external auditory meatus. 3) Identify tympanic membrane, tympanic cavity, and auditory ossicles. 4) Identify different parts of bony and membranous labyrinthine. 5) Describe cranial nerve VIII (Vestibulocochlear).  Temporal Bone Squamous External acoustic meatus Internal acoustic meatus TympanicMastoi d Gilroy et al, 2020, Gilroy Atlas, 4th Edition, Thieme Medical Publisher Inc  Temporal Bone it can see temporal bone from lateral view temporal bone has 4 parts including squamous, mastoid, tympanic, and petrous. a. above this opening it have this white part which is called squamous part b. below it can see tympanic part c. behind this opening it can see mastoid part d. from superior view of inside of cranium, it can see fourth part of temporal bone which is called petrous part ▪ petrous means rocky or stony it also has 2 meatus which are internal aquatic meatus and external aquatic meatus. o in middle of temporal bone, there is opening which is called opening of ear canal or external acoustic meatus or external auditory meatus o on posterior surface of petrous part it can see another opening which is called internal acoustic meatus ▪ in between these 2 opening external acoustic meatus and internal acoustic meatus, there is cave within petrous part in which different parts of ear (external, middle and internal ear) have embedded within petrous part.  Parts of Ear The ear has 3 parts: external, middle, and internal. o external ear consists of auricle and external acoustic meatus. o middle ear is air space in which auditory ossicles are located. ▪ second part of ear is middle ear which is cavity called Tympanic cavity it's air-filled cavity that houses tiny bones ossicles o internal ear contains membranous labyrinth. ▪ external and middle ear is concerned with collecting sound and transmitting sound A coronal section of ear towards inner ear ▪ then inner ear has 2 functions: making balance and hearing Arthur F. Dalley, II & Anne M. R. Agur. 2022, Moore’s clinically oriented anatomy, 9e. Lippincott  External Ear Conch a Tragus Lobule Auricle  External Ear External ear is composed of shell-like auricle (pinna), which collects sound, and external acoustic meatus (ear canal), which conducts sound to tympanic membrane. o auricle means ear which is composed of irregular shaped plate of elastic cartilage that is covered by thin skin which is prone to skin cancer because ear stick out from body so skin covering auricle get exposed to UV radiation so they're sight of high-risk skin cancers ▪ auricle has several depressions and elevations this marginal elevation is called Helix against Helix it have another elevation which is called anti-Helix in lower part of auricle it have 2 more elevations tragus and antitragus it can also see this deepest depression which is called Concha Lobule is made up of fat and fibrous tissue which is covered by skin and it is easily pierced for taking small blood samples and inserting earrings ▪ main function of auricle is collecting sound waves from different directions and funneling these sound waves towards opening of external auditory meatus o external auditory meatus ▪ lateral part is made up of elastic cartilage like auricle ▪ medial part is made up of temporal bone and it is covered by skin ▪ sebaceous and cerumen glands of these subcutaneous tissue of cartilaginous part produce some cerumen or earwax it protects skin of human ear canal, assisting cleaning and lubrication and provides protection against bacteria, fungi and water tympanic membrane approximately 1 cm in diameter, covered with skin externally and mucus membrane of middle ear internally o it is thin oval semi-transparent membrane at medial end of external acoustic meatus o if it view it by through otoscope, Tympanic membrane has concavity towards ear canal ▪ Apex of this concavity is called umbo o Tympanic membrane is oriented like satellite dish position to receive signals coming from ground in front or and to side of head  Innervation of External Ear The skin of auricle is The internal surface of innervated by cervical tympanic membrane is plexus (C2, C3), CN supplied by CN IX. V3, VII, and CN X. in this picture it can see innervation of external ear o if it divide auricle into 2 parts, interior to opening of external acoustic meatus is innervated by V3 mandibular nerve o posterior to that line is innervated by C2, C3 spinal nerve from cervical plexus this Concha is mainly innervated by vagus nerve and partly is innervated by facial nerve o it can also see innervation of external acoustic meatus by vagus nerve ▪ skin of superior and anterior walls of and external surface of tympanic membrane are innervated by V3 mandibular nerve  Lymphatic Drainage skin over auricle is so sensitive to UV and it's so prone to skin cancer so it should check lymph nodes around auricle The lymphatic drainage of auricle is as follows: o lateral surface of superior half of auricle drains to superficial parotid lymph nodes; o cranial surface of superior half of auricle drains to mastoid lymph nodes and deep cervical lymph nodes; o remainder of auricle, including lobule, drains into superficial cervical lymph nodes.  Tympanic Membrane Arthur F. Dalley, II & Anne M. R. Agur. 2022, Moore’s clinically oriented anatomy, 9e. Lippincott in anterior inferior quarter of tympanic membrane, it can see "cone of light" which is reflection of light of otoscope which is visible large inferior part of tympanic membrane is called pars tensa o because it is tense and it is made up of skin externally and mucous membrane internally and in between them it have some fibrous tissue small superior part of tympanic membrane is called pars flaccida because it doesn't have any fibrous tissue between skin and mucous membrane tympanic membrane moves in response to air vibrations that pass to it through external acoustic meatus o movements of membrane are transmitted by auditory ossicles through middle ear to internal ear ▪ ossicles of ear seen through tympanic membrane. Walls of Tympanic Cavity  Walls of Tympanic Cavity Tympanic cavity or cavity of middle ear which is narrow air filled chamber in Petrous part of temporal bone o it looks like box ▪ superior wall or roof of tympanic cavity is formed by thin bone which is called tegmen tympani tegmen tympani separates middle ear from middle cranial fossa it is so thin that if there is infection in this middle ear it can spreads over and it can involves meninges covering middle cranial fossa ▪ lateral wall which is covered by Tympanic membrane above Tympanic membrane there is space which is called epitympanic recess ✓ it contains some parts of ossicles ▪ in this picture medial wall has been removed so it can see inside of middle ear medial wall separates middle ear from inner ear it has projection which is called promontory ✓ it is it is formed by first or basal turn of concha of cochlear of inner ear ✓ there is Tympanic plexus on promontory ❖ it see Tympanic nerve from cranial nerve 9 glossopharyngeal nerve that make plexus and innervate mucus membrane covering Tympanic cavity above promontory, there is window which is called oval windy ✓ it is covered by this ossicles which is called stapes Below promontory, it have another window which is called round window on Superior part of middle wall there is canal of facial nerve ✓ it is continuation of canal which is on posterior wall above canal of facial nerve, there is prominence of lateral semicircular canal  Walls of Tympanic Cavity Tympanic cavity or cavity of middle ear which is narrow air filled chamber in Petrous part of temporal bone o it looks like box ▪ on floor it can see thin bone which separates middle ear from internal jugular vein anteriorly it have carotid canal that internal carotid artery passing through this canal above this canal there is opening which is opening of pharyngotympanic tube or Eustachian tube or auditory tube ✓ this tube connects middle ear to nasopharynx so air can pass through this tube to middle ear so it can equalize air pressure on either side of Tympanic membrane it also have canal which is called canal for facial nerve (cranial nerve 7) ▪ on posterior wall it have mastoid process within mastoid process it can see some packets which is called mastoid air cells ✓ all these mastoid air cells open this to this cave which is called mastoid antrum ❖ antrum means cave ❖ it opens to middle ear through this opening which is called aditus of mastoid antrum ◊ aditus means access ◊ aditus to mastoid antrum, forming posterior wall. if there is infection in middle ear it can spreads into to this mastoid antrum and it can also involves mucous membrane covering mastoid air cells which is called mastoiditis  Walls of Tympanic Cavity middle ear contains 3 tiny bones as ossicle called malleus, incus and stapes o all these 3 ossicle transmitting vibration of Tympanic membrane to oval window and then to inner ear a. handle of malleus looks like hammer handle attaches to Tympanic membrane when Tympanic membrane vibrates, it moves handle of malleus b. malleus articulates with this bone incus movement of malleus moves or vibrates incus c. incus articulates with head of stapes it can also see 2 muscles o when High peach or louder voice, these 2 muscles are contract and they can dampen amplitude or force of voice so they can prevent inner ear from damaging a. here's tensor tympani coming from cartilaginous part of Eustachian tube and attaches to handle of this malleus tensor tympani is innervated by cranial 5 mandibular branch of trigeminal nerve b. other muscle is called stapedius which is coming from this prominence pyramidal Eminence from posterior wall and it attaches to neck of stapes stapedius is innervated by facial nerve internal carotid artery is main relation of anterior wall, internal jugular vein is main relation of floor, facial nerve (CN VII) is main feature of posterior wall.  Bony & Membranous Labyrinths utricle saccule Arthur F. Dalley, II & Anne M. R. Agur. 2022, Moore’s clinically oriented anatomy, 9e. Lippincott secondary tympanic membrane  Bony & Membranous Labyrinths inner ear has 2 parts bony labyrinth and membranous labyrinth o bony labyrinth (purple) acts like cast and it houses membranous labyrinth (blue) ▪ within bony labyrinth (purple) there is fluid which is called perilymph bony labyrinth (purple) has 3 parts: a. cochlea ❖ looks like shell and it begins from vestibule and it makes 2.5 turns around this bony cone ❖ initial basal turn of cochlea make projection towards medial wall of middle ear which is called promontory ❖ below promontory it have opening which is called round window which is covered by secondary tympanic membrane b. vestibule ❖ it houses sacs which is called utricle and saccule ❖ main feature of vestibule is this opening which is called oval window ◊ oval window is covered by base of this ossicle which is called stapes c. semicircular canals ❖ contains semicircular ducts which contains membranous labyrinth ❖ these 3 semicircular canals are at right angle to each other ▪ within membranous labyrinth (blue) it have another fluid which is called endolymph the closed system of membranous tubes and bulbs, membranous labyrinth, is filled with fluid called endolymph (blue) and bathed in surrounding fluid called perilymph (purple).  Structure of Cochlea Arthur F. Dalley, II & Anne M. R. AgLippincottur. 2022, Moore’s clinically oriented anatomy, 9e.  Structure of Cochlea it can see structure of cochlea (purple) and it can see Bony Labyrinth of cochlea which houses membranous Labyrinth which is called cochlear duct o if it take cross-section in this schematic picture it can see cochlear duct separates bony Labyrinth of cochlear into 2 parts ▪ above cochlear duct it have scala vestibuli ▪ below cochlear duct it have Scala tympani o within Scala vestibule and Scala tympani, it have perilymph but cochlear duct contains endolymph Sound waves vibrating tympanic membrane → Transmission vibrations through ossicles, into this oval window → Creating pressure waves in perilymph of scala vestibuli → high frequency sound waves will vibrate proximal part of cochlear duck, but low frequency vibrates distal part of cochlear duct → Displacement of basilar membrane of cochlear duct which contains hair cells → Bending hair cells of spiral organ → action potential will happen within these hair cells → Stimulating and conveying action potentials by cochlear nerve (CN8) which carry this hearing sense into brain o Transferring vibrations across cochlear duct to perilymph of scala tympani → pressure waves in perilymph will damp by secondary tympanic membrane at round window into air of tympanic cavity.  The Vestibular System (Equilibrium or Balance) it can see vestibular system which makes equilibrium or balanced o it can see different parts of this system: saccule and utricle, ▪ it have sensory area within saccule and utricle which is called maculae Maculae maculae are sensitive to gravity and linear acceleration or deceleration. ✓ when it are moving body horizontally or vertically endolymph within utricle and saccule will move, which results in bending of hair cells of maculae so Ampullary it's stimulus primary Sensory neurons of crests vestibulocochlear nerve cranial nerve 8 within semicircular canals, it have widening which is called ampulla o into ampulla it have sensitive area which are called ampullary crest ▪ ampullary crests are sensitive to rotational movement https://open.oregonstate.education/aandp/chapter/15-4-equilibrium/ (acceleration or deceleration) of head. They are recording movements of endolymph in maculae and ampulla resulting from changing position of head. ✓ nodding, shaking or tilting from side to side ▪ when it move head, endolymph within semicircular ducts will flow which results in bending hair cells of maculae and ampullary crests which stimulates primary sensory neurons of vestibulocochlear nerve cranial nerve 8, whose cell bodies are in vestibular ganglion.  Vestibulocochlear (CN VIII) Nerve Arthur F. Dalley, II & Anne M. R. Agur. 2022, Moore’s clinically oriented anatomy, 9e. Lippincott it can see cranial nerve 8 which is called Vestibulocochlear nerve o as its name suggests it has 2 branches: cochlear nerve (nerve of hearing) and vestibular nerve (nerve of balance). ▪ cochlear nerve carrying sensory information from cochlear duct to brain so it is nerve of hearing ▪ vestibular nerve carrying sensory information from vestibular system to brain so it is nerve of balance Anatomy of Swallowing Presented by Associate Professor Bronwen Ackermann School of Medical Sciences Page 1  Overview of lecture 1) Introduction 2) Stages of swallowing (deglutination) – functional anatomy 3) Nerve supply 4) Swallowing changes over lifespan 5) Common swallowing problems Page 2  Swallowing (deglutination) Complex process - divided into 4 phases: 2. Oral phase - 1. Oral Preparatory phase - Bolus formed food leaves oral cavity 1. oral preparatory voluntar 2. oral y 3. pharyngeal involuntar 4. oesophageal y Oral preparatory stage o when it is putting food into mouth and it is trying to get it into some State for to swallow o it is getting food in and chewing Oral state o when it is starting to break down food in mouth by saliva coming in, tongue moving, food around Pharyngeal o at end it go through oropharynx which is back of oral cavity ▪ pharynx being throat into throat o food's gone out of mouth go in mouth, getting pushed out and going down throat Oesophageal phase o last stage then everything passes from Pharynx through into oesophagus 3. Pharyngeal phase - 4. Oesophageal phase- o there's blockage to oesophagus that this muscle needs to relax so that bolus traverses pharynx bolus enters oesophagus it can get food into oesophagus  Swallowing (deglutination) 1. Oral Preparatory phase - 2. Oral phase - Bolus formed food leaves oral cavity swallowing involves co-ordination with breathing processes. o while foods in mouth, it still can breathe in and out through nose mostly but it have airways open o as food starts to come back it have to do series of muscular maneuvers to make sure it close off airway and food can safely pass by into oesophagus ▪ breathing pauses briefly during swallowing to allow bolus to pass through to oesophagus 3. Pharyngeal phase - 4. Oesophageal phase- bolus traverses pharynx bolus enters oesophagus  Mastication (chewing) and Deglutination (swallowing) Involves more than 30 muscles and nerves - voluntary and involuntary. o lot of muscles in tongue alone Adults swallow ~ 600 times in daytime, and 50 times at night o keeping excess saliva out of mouth ▪ saliva is part of problem with what people aspirate with some neurological conditions Food/fluid starts to be processed from mouth to oesophagus o as food comes into mouth and it grind, it want digestion process to start ▪ if not chew food properly, this puts lot more load on rest of system o breakdown of food with saliva in mouth's highly important phase of swallowing The airways need to be protected during swallowing Marked differences between adults and infants o there's big differences through lifespan ▪ and these differences will be affected by disease particularly including neurological conditions along way  Mastication (chewing) and Deglutination (swallowing) Usually divided into 3 phases: oral (2 parts), pharyngeal and oesophageal Complex process integrating movements of: a. facial muscle (lips open then close to bring and contain food in oral cavity), ▪ conditions involving control of lips b. lingual muscle (collecting food and bolus preparation), ▪ it is looking at what happens with tongue and trying to move food around in mouth and make it shaped into this bolus bolus is Latin for “ball” c. mandibular muscle (grinding food and hold jaw closed while bolus moves back into pharynx), ▪ main Jawbone is used to grind food between molars and teeth at front canines, ripping and shredding teeth, cutting teeth so it need teeth to be in good shape to be able to chew food as well d. velar muscle (sealing off nasal cavity from food/fluid), ▪ velar is about space between nose and mouth when it eat or it is chewing and swallowing, it don't want food to come back up into nose e. pharyngeal muscle (moving bolus down into oesophagus) ▪ once food comes into oropharynx, it start to get to this mixture of involuntary phase voluntarily call on peristalsis ✓ this sequence of contractions that pushes food down into stomach that part happens involuntarily  Salivation Softening of bolus occurs via salivation o " lubricate” → it need to get it soft and mushy Saliva contains salivary amylase (ptyalin, or alpha- amylase) and lingual lipase o these begin first chemical digestion process occurs, with no further chemical digestion until food reaches stomach ▪ this is important to make it soft enough to get down to stomach because until it get to stomach there's no other breakdown that's happening ▪ Clinical: if people are NOT chewing their food and fragments are too large it run real risk of choking facial nerve facial nerve (CN7) o facial nerve supplies facial muscles and buccinator (one of muscles https://nci-media.cancer.gov/pdq/media/images/742039.jpg inside mouth) o it passes under and sometimes in parotid gland ▪ Clinical: if it have patients with symptoms of facial nerve due to inflammations or tumors in these glands, then it can affect facial nerve ▪ Clinical: quite commonly surgery of this will certainly affect facial nerve so often facial nerve gets cut in removing tumor  Salivation he major salivary glands include parotid gland, submandibular gland and sublingual gland o parotid gland: it can feel it right on top of corner angle of jaw ▪ glands can swell up for all reasons having flu, cold, fighting, infection that's why it have glands in body o Clinical: If salivary glands are damaged or aren’t producing enough saliva → it can affect taste, make chewing and swallowing more difficult facial nerve → increase risk for cavities, tooth loss, and infections in mouth. ▪ Pleomorphic adenomas (PA) are most common benign salivary gland tumours: 2-3/100,000 https://nci-media.cancer.gov/pdq/media/images/742039.jpg these are little tumors that grow in parotid gland it can get facial nerve weakness and bit of reduced saliva they can start by being benign swelling with no obvious symptoms  1. Oral preparatory stage Mastication (chewing) occurs in oral preparatory phase, with food ground into smaller particle sizes and mixed with saliva to form well-lubricated bolus for swallowing (mechanical digestion). o A greater surface area of chewed food allows more efficient breakdown by digestive enzymes and is more easily swallowed ▪ more that it can grind and mix food around before it form this bolus so longer it chew, more it's digested, easier it is to swallow in that first stage of swallowing o Greater breakdown and surface area helps release flavour and aroma ▪ tongue has taste buds for all flavor effect more it chew it, more flavor it is going to get out of food too o Food is ground up via mastication muscles (that move lower jaw/mandible) ▪ anything that happens to teeth or muscles of mastication is going to affect ability to rip, shred and grind food o Chewing and formed into bolus – action of tongue and teeth ▪ tongue is highly important in forming bolus and they're different muscles that affect facial muscles are supplied by facial nerve (CN7) masticator muscles are supplied by mandibular branch of trigeminal (CNV2) tongue is supplied by glossopharyngeal cranial nerve (CN9)  1. Oral preparatory stage muscular processes – jaw movements 1. Muscles of mastication action – masseter, temporalis, medial pterygoid and lateral pterygoid o moving mandible to grind and chew food between teeth → all these muscles are important in grinding and preparing bolus ▪ if it act unilaterally, those muscles move chin to side and pull chin to left and help grind food there masseter are on outside temporalis sits on temporal bone of skull ▪ lateral and medial pterygoid medial pterygoid on inside & masseters on outside it pushes molars together grinds food lateral pterygoid runs forward and it's involved in Big Mouth opening (involved in second half of mouth opening) ✓ it also helps with side to side movements and it can push chin forwards o muscles of mastication are supplied by trigeminal nerve (CNV) → Clinical: trigeminal neuralgia (pain that can affect ability to chew)  1. Oral preparatory stage muscular processes of tongue Only muscles in body only attached at one end! o NOTE: hyoid bone is only bone in body