Understand 1st year medicine

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Cardiovascular System: Anatomy and Physiology

Anatomy of Thorax
Thorax: Region is from
thoracic inlet to diaphragm

Thoracic aorta tributaries:

Superior vena cava

Inferior Vena Cava
I like to rise so high
Iliac, lumbar, testicular, renal, suprarenal, hepatic vein (not portal vein!)

Heart surfaces

  • Anterior (sternocostal)
  • Inferior (diaphragmatic) rests upon central tendon of diaphragm
  • Base (posterior)

1) Superior mediastinum
Angle of Louis separates superior from inferior mediastinum; and is an important anatomical landmark as it has..

  • Bones/cartilage: T4/5 and Costal cartilage for second rib
  • Respiratory: Trachea bifurcation
  • Cardiovascular: Beginning and end of aortic arch
2) Inferior mediastinum
  • Anterior: Thymus
  • Middle: Heart
  • Posterior: Aorta

Anatomy of Coronary Circulation


Coronary arteryCardiac vein
Marginal artery
Anterior interventricular artery
Posterior interventricular artery
Small cardiac vein
Great cardiac vein
Middle cardiac vein

Coronary Sulcus: Grooves in
Atrioventricular/Coronary sulcus: Separates atrium from ventricle
  • Anterior: coronary sulcus which appears on the right
  • Posterior: Coronary sulcus which appears on the left
Interventricular sulcus: Separates R&L ventricle
  • Anterior: Great cardiac vein and anterior interventricular artery
  • Posterior: Middle cardiac vein and posterior interventricular artery

muscle (Woven ridges of cardiac muscle to permit strong contraction with minimal muscle mass) in Atrium
  • Anterior portion of atrium: Present more in right than left atrium
  • Posterior portion of atrium: Absent, hence, appears smooth

Right atrium
  • Blood supply: SVC (superior vena cava), IVC (inferior vena cava), Coronary sinus
  • Coronary sinus: Drains blood from myocardium
    • From small, middle and great cardiac vein

Position of heart: 2
nd rib to 5th rib intercostal space

Papillary Muscles

  • found in heart ventricle
  • Attach to AV AtrioVentricular valves only via chordae tendinae
    • Mitral: 2 valves to so 2 papillary muscles (anterior and posterior, just like valves)
    • Tricuspid: 3 papillary muscles (anterior, posterior, septal)
  • Contract → Chordae tendinae tighten → No valve prolapse (regurgitaton) of these valves during (ventricular) systole
  • Relax during diastole so chordae tendinae loose → no resistance for blood flow from atria to ventricle

Myocardial infarction (heart attack) → Papillary muscle rupture → Valve prolapse

Atrioventricular valve

  • Mitral valve: 2 (anterior and posterior
  • Tricuspid valve: 3 (septal, anterior, posterior)

Semilunar valve
  • Aortic valve: 3 (Right - coronary, left - coronary, posterior - non-coronary sulcus) [Mercedes-Benz sign like]
    • 1% of population: 2
  • Pulmonary valve: 3 (anterior, left and right)
  • Located at the base of both pulmonary trunk (pulmonary artery) and aorta
  • NO CHORDAE tendinae
  • Passively open during systole
  • Passively close, due to cup form, during diastole to prevent backflow of blood from the arteries into the ventricles


Phrenic nerve (anterior to heart!)

Vertical path
To IVC (inferior vena cava)opening at T8

Vagus nerve

Loops around right subclavian artery
Forms posterior pulmonary plexus

Descends with subclavian vein
Solitary structure piercing

Loops around aortic arch
Forms anterior pulmonary plexus

Layers of heart

2: Endocardium/tunica intima

1: Purkinje fiber

3: Myocardium/tunica media

a. Tunica intima/endocardium (2)
  • Simple squamous epithelium
  • Fibroelastic tissue
  • Adipose tissue
  • Insulation for Purkinje below?
  • Purkinje fiber

b. Tunica media/myocardium (2)
  • Circular and spiral arrangement of heart muscle - Contraction in 3d

Purkinje fibers surrounded by top and bottom of adipose tissue

c. Tunica externa
  • Adipose tissue
  • Fibroelastic tissue
  • Visceral pericardium: Simple squamous epithelium
    • Secrete pericardial fluid

Pericardial fluid

Parietal pericardium: Serves no function?
Fibrous pericardium
  • Supportive tissue for blood vessels and nerves
  • Anchor to surround organs e.g. diaphragm
  • Prevent heart overfilling

Blood Pressure regulation

Afferent: Baroreceptor and Chemoreceptor to Medulla’s NTS

Sinus for baroreceptor
Body for chemoreceptor (b can’t pair with b!)
aortic - vagus n, carotid - glossopharyngeal n.

1. Peripheral —carotid and aortic bodies respond to low PO2, (< 60 mmHg), high pCO2 and low pH in blood. (3 things)
2. Central — in floor of 4th ventricle (medullary) responds to changes in CSF pH (H+ can’t diffuse directly into CSF... CO2 diffuses freely → CO2 + H20 -> H2CO3 -> H+ → Decrease pH

Baroreceptor reflex:
  1. Increased blood pressurestretch of the aortic and carotid sinus
  2. Increased afferent firing of the baroreceptors to cardioregulatory and vasomotor center in medulla along glossopharyngeal (for carotid) and vagus (aortic) nerves
  3. Efferent
    1. Cardioregulatory center increases PS stimulation using vagus nerve to decrease HR, decrease S stimulation to decrease HR and SV
    2. less vasomotor center firing (-> vasodilation) --> back to normal BP
Vagus nerve
  • Right: SA node
  • Left: AV node
  • Atrium
  • Ventricle: Sparsely only
  • Throughout the heart
Vasomotor nerves (sympathetic)
  • Tunica media of blood vessels
  • a-adrenergic: vasoconstriction
  • b-adrenergic: vasodilation

Innervations of the heart
  • Sympathetic: + Chronotropy (heart rate), inotropy (contractility), dromotropy (conduction velocity)
    • B-adrenoceptor
    • Thoracic sympathetic trunk: Cardiac plexus to SA node
  • Parasympathetic: - Chronotropy, inotropy and domotropy - prone to AV block
    • Muscarinic receptor
    • Vagus nerve (Cranial nerve X): Penetrates diaphragm at T10 (I ‘8’ 10 eggs at 12 - IVC-T8, Esophagus and Vagus-T10,  Aortic, -T12)

Phrenic nerve: (c345 - Diaphragm) Fibrous pericardium (right to right atrium, left to left ventricle)

Axon hillock

Action Potential
  • Heart: nodes: -60 to 0mV (phases 4, 0, 3, 4), Contractile: -60 to +20mV (phases 4, 0, 1, 2, 3, 4)
  • Neurones: add or minus 10 to contractile ... i.e. -70mV to +30; threshold potential -55mV
    • forgot the numbers just remember - resting, depol, repol, undershoot, resting)

Heart Conduction

Conduction velocity
action potential propogates along membrane by current flowing from the depolarised region to the next region at resting potential. Greater current flow → Faster the next resting segment will depolarize.
  • Cardiac contractile: -60 to +20 (80mV!!!!!) → greater current faster conduction velocity due to the voltage-gated sodium channel - goood so the muscles can contract synchronously!!!
  • Nodal:-60 to 0mV → (60mV) only -> slower current → slower conduction velocity due to the slow type voltage-gated calcium channel - AV node to delay!!!

SA (SinoAtrial) node and AV (AtrioVentricular) node: Pacemaker action potential
No phases 1 and 2; phase 4 of SAN: Heart rate, phase 0: Conduction velocity (relates to rate of depolarization)


4 - Funny currents (slow Na+ channels), T-type Ca++ channel, L-type Ca++ channels  - spontaneous depolarization; slope determines heart rate

  • ACh: slows heart rate
  • catecholamine: increase heart rate AND condxn velocity (phase 0)

0 - Upstroke - L-type Ca2+ channels - SLOW, DO NOT have fast voltage-gated Na+ channels unlike ventricular muscle, thus SLOW CONDUCTION VELOCITY (used by AV node to prolong transmission to allow atria to contract fully first before ventricles)
3 - Repolarization - K+ channel open

Depolarization from nodes to cardiac muscle: Transmitted through intercalated disks.

Cardiac muscle action potential; Phase 0-3 is ERP (effective refractory period), 4 is RRP (relative refractory period)


0 - Rapid depolarization (e.g. from adjacent cell) - If threshold potential reached (-70mV): FAST Voltage-gated Na+ channel open -> Rapid Na+ influx (increased Na+ permeability and decreased K+ permeability)
1- Initial repolarization: decreased Na+ and increased K+ permeability (opening of a special type of Cardiac transient outward potassium current)
2 - Plateau phase: Increased Ca2+ conductance matches K+ efflux
- L-type (long - distinguishes itself from nerve and skeletal muscle) calcium channels: Ca2+ entering cell  - this is when TENSION (CONTRACTION) occurs, Calcium-induced calcium release!
3 - Rapid Repolarization: increased K+ and decreased Ca++ conductance
4- Resting potential (-90mV): Highest K+ conductance and closed Ca2+ and Na+ channels
Phases 0-3: ERP - fast sodium channels not fully reactivated (back to the resting activation gates closed, inactivation gates open), therefore cannot respond to stimuli (prevent compounded action potentials!)

Phase 4: RRP - ONLY Some sodium channels back to resting form - a action potential may be evoked if the stimuli is stronger than what would normally be required

Frank Starling Law
F-S law: Cardiac output increases as EDV (end-diastolic volume) increases (up to 180mL) whereupon it will fall

+ Venous return

  • Muscle contraction due to skeletal muscles squeezing!
  • Inspiration: IVC (inferior vena cava) compression as abdominal cavity pressure > thoracic cavity pressure

CO (L/min) Cardiac Output = Stroke volume (L/beat)  x Heart rate (bpm)

Stroke volume: Volume of blood pumped by ventricle per beat
Factors affecting
  • Preload (EDV End Diastolic Volume)): Degree to which heart is stretched (EDV)
    • Increased preload → Sacromeres are stretched more → More cross-bridges form → Greater contractility
  • Afterload: Pressure the ventricles must generate to open the semilunar valves to pump the blood out of the heart
    • High afterload → Low CO Cardiac Output
    • High afterload if hypertension, aortic valve disease

SV (Inotropy)HR (Chronotropy)COExplanation
+Sympathetic+++Catecholamine → +Contractility and HR
+PS ParaSympathetic---Vagal
+Venous return+ (EDV up to 180mL then starts decreasing)Same+Frank starling law
-HR Heart Rate+-SameSlow HR allow more time for filling → increase EDV
Exercise+++S + Muscular pump (venous return)
Sudden BP--+-
+BP Blood Pressure---Baroreceptor reflex inhibits S
Excess calcium+++

 Equation to know for exams

Max HR = 220 - Age

Heart rate reserve = Max HR - Resting HR

Target heart rate: 65 to 85% of Maximum heart rate


Blood Vessel and BP Control

Autonomic innervation for blood vessels found along tunica adventitia

  1. Sympathetic innervation: alpha-adrenergic
  2. Parasympathetic innervation: blood vessels supplying salivary glands, gastrointestinal glands, and in genital erectile tissue
  • ACh and NO: vasodilatory
  • ACh release stimulates kallikrein release → kininogen to kinin
    • Kinin causes increased capillary permeability, artery vasodilation, venous constriction

Artery: Carry oxygenated blood (except pulmonary and umbilical artery); expands during systole and recoils during diastole
  1. Tunica intima: Single layer endothelium
  2. Tunica media: Thick SM (Smooth Muscle), elastin
  3. Tunica adventitia: Collagen and vasa vasorum (artery has thick wall - vasa vasorum bypasses this to allow oxygenation of artery)

Types of arteries (in order of decreasing lumen size and distance away from heart)
  1. Elastic (conducting): tunica media with many elastin; aorta, pulmonary artery
    1. not so prominent IEL (internal elastic lamina) and EEL (external elastic lamina)
  2. Muscular (distributive): THICK tunica media with many SM
    1. prominent IEL and EEL
  3. Arteriole (resistance) - steepest drop in blood pressure
    1. not so prominent IEL and EEL

Capillary: Tunica intima only (squamous endothelium - 1 cell thick to allow for diffusion), no innervation
  • Continuous: Continuous endothelium and complete basal lamina for selective filter
    • tight junction, pinocytotic vesicle
    • allow movement of small molecules only
  • Fenestrated: Fenestrated endothelium and complete basal lamina for selective filter
    • glomeruli
  • Sinusoidal: Fenestrated endothelium and incomplete basal lamina
    • form sinusoids - e.g. liver


Veins: Carry deoxygenated blood (except pulmonary and umbilical veins), collapsable because thin tunica media (SM Smooth Muscle & elastin)
  1. Tunica intima
  2. Not so prominent IEL (Internal Elastic Lamine)
  3. Tunica media: Thin compared to artery
  4. Not so prominent EEL (External Elastic Lamina)
  5. Tunica adventitia
  6. Vasa vasorum: Supply oxygen to veins!

Large veins: NO valve
  • Muscular pump: Skeletal muscle contraction presses against vein
  • Respiratory pump: During inhalation, pressure in thoracic cavity is lower than that of the abdominal cavity → abdominal veins squeezed up
Small - medium veins: Valve
  • 1-3 loose folds of tunica intima whereby the opening points to the direction of blood flow to heart
  • Blood fills the pockets to occlude lumen to prevent backflow

Pulse pressure = SP (Systolic pressure) - DP (Diastolic Pressure)
  • Low: Circulatory shock
  • High: Atherosclerosis, aortic regurgitation, PDA (Patent Ductus Arteriosus = low DP as blood rushes from systemic to pulmonary circuit)

SP: Systolic pressure
  • Dependent on cardiac output

DP: Diastolic pressure
  • Dependent on vascular resistance

Arterial end: Hydrostatic pressure
Venous end: Onctoc pressure

“Fluid shift system”  when in shock
  • Hydrostatic pressure - → Oncotic pressure constant as plasma protein stays in vessel → More fluid return
  • i.e. decreased outflow, increased inflow

Non-pitting: Myxedema (doesn't pit b/c it's not the fluid that gets displaced but the accumulation of increased MPS MucoPolySaccharide in dermis).

Pitting edema causes
  • Decreased serum protein
    • decreased synthesis - low protein intake e.g. kwashiokor, malasborption, liver disease (thus less hepatic synthesis)
    • increased loss (nephrotic syndrome - foamy urine!!!)
  • Increased venous pressure (CHF Congestive Heart Pressure, venous thrombosis)
  • Capillary edema (vasculitis)

Differential for hypo/normo-albuminemia

If <40s, hypoalbuminemia (increased loss or decreased synthesis)
If >40s normoalbuminemia (i.e. cause is venous hyperten)

  • Protein RICH
  • Initial pitting → Late NON-pitting edema due to fibrosis
  • Characteristic: nontender, painless, UNILATERAL
  • Cause: abnormal lymphatic drainage (commonly due to malignancy)
    • upper extremity - breast cancer, surgery/radiation for breast cancer
    • lower extremity - aplasia of lymphatics, or secondary to inflammation (strep infxn), obstructive (UNIlateral - malignancy e.g. men - prostate, women - lymphoma)

Baker’s cyst
  • popliteal cyst -swelling of  synovial fluid  between tendon of medial head of gastroc and semimembranosus muscle, posterior to medial femoral condyle
  • NOT an actual cyst
  • Cause: Arthritis, meniscus tear
  • If large enough to rupture → acute pain and swelling of calf muscle

DVT (Deep Vein Thrombosis)
  • Unilateral
  • Tender
  • Swelling
  • Redness
  • Warm

Circulatory shock: Inadequate perfusion resulting in compromised organ function
  • Clammy and cold skin (Sympathetic → muscarinic sweat glands and vasoconstriction)
  • Pale skin (peripheral vasoconstriction)
  • Tachycardia
  • LATE SYMPTOM: Hypotension (no longer able to maintain BP despite HR and SV)

Classes of circulatory shock
  1. Hypovolemia shock: Low blood volume (less than normal 5L/min)
    1. Hemorrhage, dehydration due to diarrhea, burn
  2. Distributive shock: Excess vasodilation
    1. Anaphylactic shock, sepsis (bacterial blood infection)
  3. Cardiogenic shock: Heart not pumping enough to meet demands
    1. Post MI
    2. Arrythmia (e.g. VF Ventricular Fibrillation)
    3. Valve stenosis

MAP (Mean arterial pressure): ⅓ SP + ⅔ DP (2/3 as diastolic lasts longer than systolic)

BP Blood Pressure or MAP Mean Arterial Pressure = CO (Cardiac Output) x TPR (Total peripheral resistance) ; CO = HR (Heart rate) x SV (Stroke volume)
  • HR: If increase, CO increase, thus BP increase
  • Blood volume: If increase, CO increase, thus BP increase
    • RAAS system - renin angiotensin aldosterone system
  • TPR (Total peripheral resistance)
  • Vessel resistance (R) is directly proportional to the length (L) of the vessel and the viscosity (η) of the blood, and inversely proportional to the radius to the fourth power (r4)
  • Viscosity (n) of blood: Hematocrit
  • Length (L) of vessel: The longer the greater resistance
  • Radius (r) : Resistance is inversely proportional to radius4 (i.e. if radius halves, resistance increases by a factor of 16)
    • NE (Norephinephrine), E (Epinephrine) to alpha-1 receptor →  vasoconstriction

Blood Pressure regulation

1. Peripheral —carotid and aortic bodies respond to low PO2, (< 60 mmHg), high pCO2 and low pH in blood. (3 things)
2. Central — in floor of 4th ventricle (medullary) responds to changes in CSF pH (H+ can’t diffuse directly into CSF (cerebal spinal fludi) ... CO2 diffuses freely → CO2 + H20 -> H2CO3 -> H+ → Decrease pH

Baroreceptor reflex:
  1. Increased blood pressurestretch of the aortic and carotid sinus
  2. Increased afferent firing of the baroreceptors to cardioregulatory and vasomotor center along glossopharyngeal (for carotid) and vagus (aortic) nerves to medulla (solitary nucleus)
  3. Efferent
    1. Cardioregulatory center increases PS stimulation using vagus nerve to decrease HR, decrease S stimulation to decrease HR and SV
    2. less vasomotor center firing (-> vasodilation) --> back to normal BP

Efferent from medulla
Cardioregulatory center: Vagus nerve: HR only
  • Right: SA node
  • Left: AV node
  • Atrium
  • Ventricle: Sparsely only
Cardioregulatory center: Sympathetic: HR and contractility, thus SV
  • Throughout the heart
Vasomotor nerves (sympathetic)
  • Tunica media of blood vessels
  • a-adrenergic: vasoconstriction
  • b-adrenergic: vasodilation

High pulse pressure
  1. Endothelial damage of arteries
    1. Hypertension, Diabetes
  2. Endothelium express adhesion molecules to recruit monocytes and platelet; and attract lipids
  3. Attracted monocytes differentiate to macrophage to ingest lipid → foam cell
  4. Attracted macrophage and platelet secrete cytokines that induce
    1. SM hyperplasia
    2. SM migrate from tunica media to intima (myointimal cell) and change from a contractile to a repair phenotype  to stabalize the lesion
    3. Fibrous cap formation: Smooth muscle, foam cell, inflammatory cell, Extracellular matrix
      1. Overlies necrotic center (cholesterol crystals, foam cells)

Complications of atherosclerosis
  • Vessel weakness (aneurysm
  • thrombosis
    • Atherosclerotic plaque prone to rupture → Expose subendothelial collagen → Thrombus formation → Ischemia
  • HT (e.g. activate RAAS)

BP Regulation: RAAS

Effects of AT2
  • Sympathetic
  • Potent vasoconstrictor (arteriole in systemic, efferent arteriole in glomerular)
  • Stimulate thirst
  • Stimulate adrenal gland to release aldosterone
    • Salt (aldosterone) : Zona glomerulosa
    • Sugar (glucocorticoid): Z. fasciculata
    • Sex (FSH and LH) : Z. reticularis
  • Stimulate posterior pituitary to release ADH (anti-diuretic hormone)
  • Stimulate Na+/H+ exchanger on apical membrane of PCT (proximal convoluted tubule) → more Na+ absorption

3 things that stimulate renin release
  • Low BP sensed by JG
  • Low Na+ sensed by macula densa
  • Sympathetic

Angiotensinogen (Liver) -(Renin from JG cell of kidney)-> AT1 -(ACE from lung)-> AT2 → Aldosterone


Gastrointestinal System


Anterior Abdominal Wall

Skin → Superficial fascia (Fatty camper’s fascia → Membranous scarpa’s fascia) → Muscle → Transversalis fascia → Peritoneum

Fascia: CT Connective Tssieu that surrounds muscles, BV Blood Vessel, nerves

  • superficial: scarpa
  • deep (of muscles): transversalis fascia
  • visceral: peritoneum

External oblique → Internal oblique → Transversalis
Linea alba, linea semilunaris (curved tendinous line on either side of rectus abdominis)

Transpyloric plane L1, subcostal plane L2, umbilicus L3, Trans/intertubercular line L4



McBurney’s Point: ⅓ between ASIS (Anterior superior iliac spine) and umbilicus

  • Where appendix attaches to cecum
  • Acute tenderness: Acute appendicitis
    • rebound tenderness: upon removal of pressure that it hurts


Posterior abdominal wall
  • Diaphragm
  • Arcuate ligament
    • Median: connects right and left crus of diaphragm to form the aortic hiatus; crura = structure extending inferiorly from diaphragm to vertebral column
    • Medial: over psoas major muscle, also allows passage of sympathetic trunk; from L1
    • Lateral: over quadratus lumborum muscle; from the 12th rib to the 1st lumbar vertebrae
  • Muscle
    • quadratic lumborum: transverse process of 12th rib and L1-4 to posterior part of iliac crest to laterally bend the trunk
    • psoas major and minor: transverse process of lumbar to lesser trochanter to flex thigh
    • iliacus: iliac crest to femur lesser trochanter to flex thigh
    • ilipsoas: transverse process of lumbar vertebrae and iliac fossa to lesser trochanter to flex thigh
    • diaphragm
  • Nerve
    • Sympathetic trunk
    • Subcostal nerve (T12)
    • Lumbar plexus (L1-L4)


General histology throughout GI (GastroIntestinal) tract
  1. Mucosa
    1. epithelium
    2. lamina propria - CT Connective Tissue; lymphoid cells or nodules e.g. tonsils, ileum, appendix; lacteal in small intestine
    3. muscularis mucosae
  2. Submucosa
    1. CT
    2. Vascular plexus that gives rise to capillary bed of mucosa
    3. Meissner's plexus
    4. Submucosal glands in esophagus and duodenum (Brunner’s glands)
  3. Muscularis externa
    1. Inner circular
    2. Auerbach's plexus:
    3. Outer longitudinal
    4. Tenia coli: 3 x outer longitudinal in colon
      1. Contracts length-wise to produce haustra (like baggy pants with a “thing” sticking)
  4. Adventitia or serosa
    1. adventitia if surrounded by ordinary CT
    2. serosa if if surrounded by CT + mesothelium (simple squamous) to give it a nice end
      1. visceral peritoneum
      2. continues over abdominal wall as parietal peritoneum


Distal ⅓ Skeletal muscle

Middle ½ skeletal muscle ½ smooth muscle

Proximal ⅓ Smooth muscle

Stomach with rugae

Rugae: folds that allows stomach to expand

Three layers of muscles
  1. Inner oblique
  2. Middle circular
  3. Outer longitudinal

Glandular cells
  • Goblet cell: Produce Mucous
  • Enteroendocrine / G cell: Produce gastrin → stimulates HCl secretion, gastric motility
  • Parietal cell: Produce HCl and Intrinsic factor (aid Vit. B12 absorption)
  • Chief cell: Produce Pepsinogen

Small intestine with plicae circulares

Function: Absorb nutrients

Plicae circulares: folds like rugae in stomach but do not obliterate when extended
These folds slow the passage of food and increase SA for absorption. Add to that the villi and in each villi microvilli!

  • Duodenum: Brunner’s glands (submucosal gland): mucus rich bicarbonate
    • lubrication
    • neutralize acidity of chyme from stomach
    • pH environment for intestinal enzyme
  • Jejunum: Prominent plicae circulares
  • Ileum: Peyer’s patch (M cells - antigen uptake and delivers the intact antigen to underlying APC in the pocket beneath)

Jejunum: Thick wall, prominent plicae circulares, less fat, simple arcade
Ileum: Thin wall, less prominent plicae circulares, more fat, multiple arcade

Parts of duodenum
  1. Superior
  2. Descending: Duodenal papilla
  3. Horizontal
  4. Ascending: Ligament of Treitz (a suspensory muscle) attaches this to diaphragm

Large intestine with haustra

Function: Absorb water, produce vitamin K

Appendices epiploicae: Peritoneum + fat
(Vermiform) Appendix: Blind-ended tube connected to cecum
  • Safehouse for colonic bacteria
  • Flushed if diarrhea
Colonic bacteria

Mouth to second part of duodenumSecond part of duodenum to splenic flexure of colonSplenic flexure to rectum
Vagus nerveVagus nervePelvic splanchnic (PS)
Celiac arterySMA (superior mesenteric artery)IMA (interior mesenteric artery)
Celiac lymph nodeSuperior mesenteric lymph nodeChyle cistern (L1/2)

Celiac trunk branches
  • Left gastric
  • Common hepatic artery (after branching off gastroduodenal artery → proper hepatic artery)
  • Splenic artery

Liver Anatomy

Pancreas Anatomy

  • Superior mesenteric artery and vein cross in front of the uncinate process.

Anatomy of 2nd part of duodenum

Ampulla of Vater: Ampulla = dilated portion (e.g. semicircular canal) - where things come together...

Sphincter of Oddi: Controls flow of digestive juice through ampulla of Vater into second part of duodenum
  • Relax if CCK (duodenal hormone)

Duodenal Papilla: Nipple
  • Major: Opening of ventral pancreatic duct
  • Minor: Opening of accessory (dorsal) pancreatic duct