HTHSCI 1DT3 Lecture 9: anatomy sur-61-68
26 Dec 2020
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The 3 tenia coli fuse around the rectum to form a continuous muscle layer. Middle and inf. rectal arteries and veins. White line = where anal canal becomes true skin. Deep segment of external sphincter which is continuous c puboretalis muscle (part of levator ani) Palpable on pr ~5cm from the anus. Demarcates junction between anal canal and rectum. Subcutaneous bleeding from a burst venule caused by straining or the passage of hard stool. Also called an external pile: a misnomer. Tender blue lump at the anal margin. Anal cushion: mass of spongy vascular tissue. Positioned @ 3, 7 and 11 o"clock. Where the three major arteries that feed the vascular plexuses enter the anal canal. Gravity, straining engorgement and enlargement of anal cushions. Hard stool disrupts connective tissue around cushions. Cushions protrude and can be damaged by hard stool. Haemorrhoids arise above dentate line not painful. May be gripped by anal sphincter thrombosis.
