Useful anatomy

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All details are arranged in a head-to-toe, up-to-down manner. ie Anatomy related to the head at the top; Anatomy related to the foot at the bottom; Everything else in between.


Cerebral circulation:
Anterior cerebral circulation segments: (Classification varies among different systems)
A1: Origin <---> Ant.Communicating Artery (AComm)
A2: AComm <---> Branch point for callosomarginal artery
A3: Branch point for callosomarginal artery <---> 3cm posterior to the genu of corpus callosum
A4: Pericallosal artery
A5: Terminal branch of ACA

Middle cerebral circulation segments: (Classification varies among different systems)
M1: Origin <---> Bifurcation of MCA
M2: Bifurcation <---> Cortical branches (on the insula)
M3: Within the sylvian fissure <---> Cortical surface of cerebral hemisphere
M4: Distal branches of MCA

Posterior cerebral circulation segments: (Classification varies among different systems)
P1: Origin <---> Post.Communicating Artery (PComm)
P2: PComm <---> origin of Inferior temporal artery
P3: Origin of Int.temporal artery <---> terminal branches
P4: Cortical branches


Thyroid gland measurements (Ultrasound)
Isthmus up to 0.3 cm

Each lobe:

- Length (Superior-Inferior): 4 - 6 cm

- Thick (Anterior-Posterior) / Width (Medial-Lateral): 1.3 – 1.8 cm


Gilula's arch / lines

Red arch: 1st arch: Scaphoid-Lunate-Triquetrum
Purple arch: 2nd arch: Scaphoid-Lunate-Triquetrum
Yellow arch: 3rd arch: Capitate-Hamate

Scapho-lunate angle

Green: Scaphoid ; Orange: Lunate
Blue axis: Scaphoid axis ; Red axis: Lunate axis
Purple angle (alpha): Scapho-lunate angle. Normal 30-60 degrees in neutral position

Liver span: (Ultrasound)
Right mid-clavicle plane: 13-17 cm

Couinaud system of the liver segments:
Segment 1 to 8, including 4a & 4b.
Each segment is divided by Hepatic veins & left Portal vein
Portal veins lie in each segments (except left Portal vein)

Segment 1: Caudate lobe
Segment 2: Superior, lateral of left lobe
Segment 3: Inferior, lateral of left lobe
Segment 4a: Superior, medial of left lobe
Segment 4b: Inferior, medial of left lobe
Segment 5: Inferior, anterior of right lobe
Segment 6: Inferior, posterior of right lobe
Segment 7: Superior, posterior of right lobe
Segment 8: Superior, anterior of right lobe
*Looking at the liver from the front, count each segment clockwise.


Hepatic artery (Ultrasound)
Diastolic velocity <20cm/s
Resistant Index (RI) ~/= 60-70%


Hepatic vein flow (Ultrasound)
Triphasic waveform (related to atrial contractility)
Waveform also affected by breathing
Hepatofugal


Portal vein (Ultrasound)
Hepatopetal flow (flow towards the liver parenchyma), minimal pulsatility

Normal flow velocities: 20 - 30 cm/s (fasted patient)
Normal PV diameter =/< 13mm (at main PV)

A good article more on US Portal vein variability - physiological and pathological
http://bjr.birjournals.org/content/75/899/919.full

Intrahepatic ducts (Ultrasound)
<40% diameter of its adjacent PV
=/< 2mm (peripheral ducts)


Common duct of the biliary system: (Ultrasound)
Duct diameter </= 6mm + Add 1mm for each decade after 60yo
Post-cholecystectomy: 8-10mm
Wall thickness =/< 5mm

Gallbladder

- transverse dimension 4cm

- length usually up to 10cm

- wall thickness up to 3mm

Pancreas thickness
Head <3cm
Body <2.5
Tail <2.5cm

Spleen
- Coronal plane Length =/< 13 cm
- Thickness: Hilum to the opposite border =/<6cm


Kidney
Bipolar length 9 - 13cm
Roughly 3.5 lumbar vertebrae plus the disk spaces (on radiograph)
Left kidney can be longer than the right, up to 2cm
*If right kidney is larger than the left, look for right duplex collecting system

*Actual length varies with body size and age of patient

Urinary bladder wall

under-filled: 5mm

well-distended: 3mm

Testis
Size 15-20 mL (4-5 x 2-3 x 2-3 cm)
Scrotal vein max. 2mm diameter

Endometrial thickness

Endometrial stripe (aka endometrial complex): 

- Made up of two layers of endometrium

- Thickness varies with menstrual cycle

End of menstruation	2-3mm thick	Hyperechoic, well defined
Mid cycle	Up to 8mm thick	Hyperechoic, well defined Occas Trilaminated stripe
Secretory phase	~15mm or more	Hyperechoic, less well defined
Menstruation	Thins out again

- Post-partum endometrial stripe <15mm thick

- Menopause endometrial stripe =/< 5mm thick

Uterus size

Neonate	Prominent uterus & Cx	Due to maternal hormone
Prepuberty	Similar / less prominent in relative to Cx	Maternal hormonal effect wears off
Nulliparous	7 x 5 x 3 cm (L x W x AP)
Parous		Increase w/ each parity
Post-partum	Back to baseline by 7/52	Length is the most reliable indicator
Menopause	Atrophies (prepubertal size)	Def: 1yr post-menopause

Nulliparous:

Cervical canal
30-40mm
Fallopian tube
interstitial, isthmic, ampullary, infundibular segments
5-16cm


Ovaries
- Volume varies with stage of menstrual cycle

- Premenstrual: further divided to 4 age groups with varying sizes

- Nulliparous 9.0 mL - 15/20mL (L x W x AP x 0.5): (3x3x2 x 0.5) 

- Parous 15mL - 20mL (L x W x AP x 0.5): (5x3x2 x 0.5) 

- Menopause:

-          Atrophies

-          Abnormal if: (1) > 15 / 20 mL and/or (2) one ovary is twice the size of the other

Hesselbach's triangle
Site of inguinal hernia. Bordered by:
(1) Inguinal / iliopectineal ligament
(2) Inferior epigastric artery
(3) Lateral border of rectus abdominis
Floor: Transversalis fascia