Anatomy Practical 1 Flashcards
What are the phases of eating and swallowing?
1) oral phase: voluntary control (motor cortex and cortical areas)
2) Pharyngeal phase: co-ordinated by swallowing centre in medulla oblangata and pons, reflex initiated by touch receptors in pharynx as bolus of food gets push to back of mouth by tongue
3) oesophageal phase: ANS coordinated
How does tongue push bolus to the back of the mouth?
Elevates the hard palate using intrinsic muscles of the tongue
What is laryngeal closure?
primary laryngopharyngeal protective mechanism to prevent aspiration during swallowing
vocal fold adduction and retroversion of epiglottis
anatomically directs food bolus laterally towards piriform fossa
What is the oesophageal phase?
involuntary neuromuscular control
propagation of food bolus is slower than in pharynx
bolus enters oesophagus and is propelled downwards by striated muscle first then smooth muscle
upper oesophageal sphincter relaxes letting food pass
striated constrictor muscles of pharynx + peristalsis + relaxation of LOS = bolus is pushed through oesophagus into stomach
What are some risk factors for aspiration of foreign materials into the lungs?
- poor gag reflex in unconscious after stroke/brain injury
- drinking large amounts of alcohol
- general anaesthesia
- old age
- swallowing problems
- coma
- being less alert due to medicines, illness
What is the oesophagus?
fibromuscular tube
2cm diameter
pharynx to stomach
What is the position and direction of the oesophagus?
in between trachea and vertebral column
descends in posterior mediastinum passing posterior to right of arch of aorta and left atrium
deviates to left behind pulmonary artery and left bronchus passing through oesophageal hiatus at T10 vertebra to reach stomach
What is posterior, anterior and to the left and right of the upper oesophagus?
Posterior - vertebral column
Anterior - trachea
on both sides - dome of pleura and superior lobe of each lung
What is posterior, anterior and to the left and right of the lower oesophagus?
Posterior - vertebral column
Anterior - heart (LA)
Left - descending thoracic aorta
Right - azygos vein and inferior lobe of right lung
What are the oesophageal sphincters?
UOS -> voluntary skeletal muscle comprised of inferior pharyngeal constrictor/cricopharyngeus
LOS -> specialised segment of circular muscle layer of distal oesophagus, first anti-reflux barrier protecting oesophagus from acidic gastric content
What are the levels of the upper and lower oesophagus?
Upper - C6-T4
Lower - T4-T10
What is a crus?
one of two tendinous structures that extends below the diaphragm to the vertebral column
What is the costal margin?
lower edge of the chest (thorax) formed by the bottom edge of the rib cage.
What is a hiatus hernia?
protrusion of upper part of stomach into thorax through tear/weakness in diaphragm, often result in heartburn but can cause chest pain with eating, most common cause is obesity
What is the most common form of hiatal hernias?
sliding hiatus hernias
What is the inguinal ligament?
Thickening of the external oblique aponeurosis spanning from ASIS to pubic tubercle of pelvis
What is the inguinal canal?
A space passing obliquely through abdominal wall in the inguinal region, found over medial half of inguinal ligament
formed by anterolateral muscles of abdominal wall (external and internal oblique and transversus abdominis) and their aponeuroses
What are the openings of the inguinal canal?
- deep internal ring: opening in transversalis fascia located at midpoint of inguinal ligament, halfway between ASIS and pubic tubercle
- superficial external ring: opening in external oblique aponeurosis, located above pubic tubercle
What does the inguinal canal contain?
Male - spermatic cord and ilioinguinal nerve
Female - round ligament of the uterus and ilioinguinal nerve
What is a hernia?
A protrusion of a tissue/structure/part of an organ through a wall which normally contains it
Areas of abdominal wall may be weak so predisposed to contents protruding through them
How do hernias usually present?
As a lump/mass with/without pain
Why are hernias clinically important?
Bowel lumen can become obstructed or strangulated (blood supply in its wall cut off) requiring surgical intervention
What are the causes of hernia?
1 - anything raising intra-abdominal pressure (excessive coughing, lifting, heavy weights)
2- anything weakening/stretching abdominal wall (old age, incision from operation, obesity, pregnancy)
What are the most common hernias?
Inguinal and femoral
What is the femoral canal?
A space found in the femoral triangle
Medial to femoral vein containing lymphatic vessels and lymph gland
What are inguinal hernias classified as?
Direct - protrude through abdominal wall (often through Hasselbach’s triangle)
Indirect - pass through deep inguinal ring and can extend through inguinal canal out of superficial ring into scrotum
What is the peritoneum?
Continuous serous membrane sitting on abdominal cavity lining abdominal viscera completely or partially
Visceral peritoneum covering organs and parietal covering body wall
potential space between 2 layers containing serous fluids allowing organs to slip over one another friction free
What are intraperitoneal organs?
Organs engulfed within the peritoneum
positions can vary and are not fixed
What are retroperitoneal organs?
Organs which press from behind
In fixed posiitons
What are ligaments, mesentery and omentum examples of? What is their function?
Folds - as organs press into peritoneum they form folds providing double layers of peritoneum
- carry nerves, blood vessels, lymphatics and provide support for viscera
What is the mesentery?
Folds of visceral peritoneum that arise from posterior abdominal wall and extend to jejunum and ileum
What is the mesentery proper?
part of the mesentery suspending the small intestine
What is the omentum?
greater and lesser
greater - larger double layer of visceral peritoneum starting from greater curvature of stomach hanging down in front of small intestine then double layer folds back on itself and attaches to back of transverse colon
lesser - double layer of peritoneum extending from liver to lesser curvature of stomach and part of duodenum
What does the falciform ligament attach?
Liver, anterior abdominal wall and diaphragm
What is laproscopy?
process of viewing inside the abdomen using fibre optic camera
What are adhesions?
Inflammation/incisions causes scarring = two layers of peritoneum can stick together and limit movement of internal organs
What are the two types of abdominal pain?
visceral pain - layer sparsely innervated hence produces dull, poorly localised pain
parietal pain - richly innervated by somatic nerves, causes well localised sharp pain
What does the foregut, midgut and hindgut contain?
Foregut - liver, gall bladder, pancreas, spleen, proximal duodenum
Midgut - distal duodenum, jejunum, ileum, caecum, appendix, ascending colon, 2/3 transverse colon
Hindgut - 1/3 transverse colon, descending colon, sigmoid colon, rectum
What are the levels of the foregut, midgut and hindgut?
foregut - T6-T9
midgut - T8-T12
hindgut - T12-L2
Where does the thoracic aorta become the abdominal aorta?
T12 when it passes through the diaphragm
What is the blood supply to the gut derived from?
Abdominal aorta via 3 main arteries - coeliac trunk, SMA, IMA
What are the branches of the SMA?
- branches to jejunum and ileum
- 3 large branches supplying colon
- 15-18 branches to small bowel which unit forming arches
What is the marginal artery?
Where the SMA and IMA overlap
What is mesenteric ischaemia?
occurs as a result of blockage of blood supply to gut from IMA or SMA due to thrombus/embolus formation causing abdominal pain, vomiting, bloody stool and can result in gangrenous bowel and death if blood supply not restored within 24/48 hrs
What is the position of the sigmoid colon?
Starts anterior to pelvic brim, below it is continuous with rectus, intraperitoneal, mobile and forms a loop, attached to posterior pelvic wall by fan shaped sigmoid mesocolon
Where does rectum start?
anterior to 3rd sacral vertebra
How can a sigmoid volvulus occur?
Sigmoid colon is mobile so can rotate around mesentery, may correct itself spontaneously or rotation may continue until blood supply is shut off, rotation occurs commonly clockwise
What is the position of the rectum?
Follows curves of sacrum and coccyx
Ends at tip of coccyx by piercing pelvic diaphragm and becoming continuous with anal canal
Lower 1/3 devoid of peritoneum covering
What is the puborectalis?
Portion of levator ani muscle forming a sling at the junction of rectum with anal canal pulling bowel forward producing anorectal angle
blend with deep fibres of external sphincter
What blood supply is there to the rectum?
superior, middle and inferior rectal arteries
superior rectal artery is direct continuation of inferior mesenteric artery
middle rectal artery is small branch from internal iliac artery
inferior rectal artery is branch of pudendal artery anastomosing with middle rectal artery at anorectal junction
What is the anal canal?
Last part of large intestine
starts at anorectal junction at level of pubo rectalis muscle
split into 2 sections - upper and lower divided by pectinate line
What is the upper part of the anal canal?
Originates from the embryological endoderm (hindgut) at the anorectal junction
has anal columns of Morgagni joined by anal valves inferiorly marking inferior border of upper part of anal canal and secrete mucous on defaecation
blood supply and drainage by superior rectal artery and vein
How is the innervation different above and below the pectinate line?
above - visceral nerve supply coming from hypogastric plexus, sensitive to stretch
below - somatic, from inferior rectal nerves, sensitive to pain/temp/touch
What is the blood supply to the lower half of the anal canal?
Inferior rectal artery
divided into 2 zones separated by Hilton’s white line (anal verge)
What are the anal sphincters?
Internal - involuntary smooth muscle sphincter supplied by PS fibres passing through pelvic splanchnic nerves, sphincter relaxes in response to pressure distending rectal ampulla
external - voluntary innervated primary by S4 through inferior rectal nerve
Where are the anal cushions?
At the level of the pectinate line
What are prolapsed haemorrhoids?
Lump around anus, may need to be pushed back or may return to anal canal on their own after bowel movement
some unable to be pushed back and can become extremely painful but haemorrhoids generally not painful
symptoms may also be seen in patients with colorectal cancer
