Anatomy Flashcards
Sulci of the heart
Coronary sulcus (atrioventricular groove) travels transversely around the surface of the heart (between atria and ventricles) Anterior and posterior sulci; run vertically on their respective sides separating left and right ventricles.
Surface landmarks of heart
left and right auricles (function to increase atrial capacity).
Apex (bottom).
Base of heart (along atrioventricular valve line).
Superior border (base of vessels entering heart).
Right and left borders.
inferior border.
Describe hearts positioning
fist sized organ, located slightly to the left within the thoracic cavity (in the middle mediastinum). The in situ positioning of the heart means the heart lies obliquely, with the right side sitting anteriorly and the left posteriorly. The apex of the heart sits around the 5th intercostal space.
Endocardium
Endocardium: Innermost layer of cardiac wall, lining cavities and valves. Is comprised of loose connective tissue and its function is to regulate contractions and aids embryonic development. Endocarditis is inflammation to this layer, it occurs most frequently in the valves of the heart, commonly caused by bacterial infection. Endocarditis can cause heart murmurs and once contracted are likely to reoccur.
Subendocardium
Subendocardium: Layer between the endocardium and myocardium. This layer joins the endo and myocardial layers. Composed of loose fibrous tissue, it contains vessels and nerves (including purkinje fibres). Damage to this layer arrhythmias due to containing elements of the conducting system.
Myocardium
Myocardium: Cardiac muscle (involuntary striated muscle). Is responsible for contractile force. Myocarditis is inflammation to this layer from a virus. Causes chest pain, shortness of breath and tachycardias.
Subepicardial: layer between the myo and epicardial layers.
Epicardium
Epicardium: Hearts outermost layer; formed by visceral layer of the pericardium. Composed of connective tissue and fat. Connective tissue secretes a small amount of lubricating serous fluid into the pericardial cavity. Outer layer is lined by squamous cells.
Pericardium and functions
Fibrous sac surrounding the heart and great vessels. It is innervated by the phrenic nerve.
Two main layers:
Fibrous - continuous with central tendon of diaphragm, tough connective tissue, non-distensible, function to prevent rapid overfilling.
Serous - Further divided into two layers: outer parietal and inner visceral. Parietal lines the fibrous pericardium and the visceral lines the epicardium of the heart. Made of a single layer of epithelium called mesothelium.
Functions of the pericardium:
Prevent overfilling of the heart
fix the heart in position
lubrication
Protection from infection (physical barrier)
Pericardial sinuses
Transverse pericardial sinus - Superior to the heart (left atrium), posterior to the ascending aorta and pulmonary trunk, anterior to the SVC. Separates the arterial from venous vessels. Can be used to identify and ligate vessels during coronary artery bypass surgery.
Oblique pericardial sinus - Blind ending passage posterior to the heart surface
Right atrium
receives deoxygenated blood from the SVC, IVC and coronary veins. Blood is then pumped through to the right ventricle via the tricuspid valve. The right auricle is located in the antero-medial portion. Interior is separated into two by a muscular ridge termed the crista terminalis. Posterior to the crista terminalis is the sinus venarum. This has smooth walls and is derived from the sinus venosus. Anterior to the crista terminalis is the atrium proper, derived from the primitive atrium. This has rough, muscular walls formed from the pectinate muscles. The coronary sinus receives blood from the coronary veins and opens into the right atrium between the IVC and the atrioventricular orifice.
Left atrium
receives oxygenated blood from the pulmonary veins, passes through to the left ventricle via the mitral valve. Posterior border of the heart (in its anatomical position). Left auricle extends from the superior aspect of chamber to overlap the pulmonary trunk root. Divided into two by embryological origin: INFLOW PORTION: surface is smooth, is derived from the pulmonary veins. The OUTFLOW PORTION: is anteriorly located, includes the left auricle. Is lined by pectinate muscles and is derived from the embryonic atrium.
Right ventricle
receives deoxygenated blood from the right atrium, pumped through to the lungs via the pulmonary artery. Forms the majority of the hearts anterior border (anatomical position). Divided into two parts: INFLOW portion: lined by trabeculae carneae muscles (irregular muscles). OUTFLOW portion: superior aspect of the ventricle, termed the conus arteriosus. Has smooth walls and NO trabeculae carnage. Derived from the bulbus cordis.
Left ventricle
receives oxygenated blood from the left atrium, passes to the systemic circulation via the aorta. Also divided into two: INFLOW portion is lined with trabeculae carneae with two papillary muscles to hold onto the mitral valve. OUTFLOW portion is termed the aortic vestibule (goes into the aorta!). Has smooth walls and is derived from the bulbus cordis.
Valves of the heart
Atrioventricular: tricuspid and mitral valve found between atria and ventricle. Both secured with base of each cusp anchored to FIBROUS RING surrounding orifice. Held in place by CHORDAE TENDINAE attached to papillary muscles in turn attached to the cardiac wall. contract in systole to prevent backflow of blood Tricuspid - 3 leaflets, mitral - 2. Mitral is only valve with ‘true’ leaflets better for functioning, has to resist greater pressures.
semilunar: Close at beginning of DIASTOLE. pulmonary valve- 3 cusps, aortic valve - 3 cusps. Aortic valve leaflets are slightly dilated on the sides, creating the aortic sinus (marks place of coronary arteries) supplies the heart with blood during DIASTOLE
Ascending and arch of the aortic branches
Ascending aorta - coronary arteries
Arch of aorta -
Brachiocephalic artery
left common carotid
left subclavian artery
Coronary arteries
Arise from the coronary sinus; Left and Right Coronary arteries.
Left: passes between left pulmonary trunk and left auricle before dividing into the left anterior descending (LAD)/ left atrioventricular artery. LAD travels interventricular groove to the apex and anastomoses with posterior IV branch. LCA also gives off a main branch (left marginal artery) and left circumflex artery. Circumflex travels round to the posterior surface.
Right: Passes to right of pulmonary trunk along coronary sinus. Branches into Right marginal artery which moves along right and inferior border toward the apex. In 80-85% population, the RCA branches into the posterior interventricular artery. This travels along the post. interventricular groove to anastomose with the LAD.
Cardiac veins
Great cardiac vein: originates from apex follows anterior atrioventricular groove around to left side of coronary sulcus. Main vein.
small cardiac vein: anterior surface passes to right side
middle cardiac vein: posterior surface
left marginal vein: posterior surface on left side
left posterior ventricular vein: posterior side in interventricular sulcus to the coronary sinus.
All drain into the coronary sinus
Cardiac conduction cycle
Myocardial cells have auto-rhythmicitiy so can contract by themselves due to having their own intrinsic firing rate.
This auto-rhythmicity is fastest in the SAN, and so this is the heart’s pacemaker
SAN is a cluster of cells in right atrial wall just inferior to the SVC entrance. These cells have the fastest depolarisation rate and so determine heart rhythm (apx. 70-80BPM; the sinus rhythm)
impulse created by SAN travels along intra-atrial conduction network to contract both atria simultaneously (ATRIAL SYSTOLE). Also travels along inter-nodal pathways to AVN
AVN is located in inter-atrial septum, above tricuspid valve. Has slower depolarisation rate (40-60BPM). Once AVN receives impulse from SAN there is a small delay to ensure atria have fully emptied before ventricular systole takes place.
Impulse travels down Bundle of His fibres in septum
passes to left and right bundle branches also within septum
Rapidly travels to purkinje fibres in the apex of the heart
Impulse then spreads to ventricular myocardium causing simultaneous contraction of ventricles (total time elapsed so far roughly 0.22seconds)
total time is 0.8seconds
Cardiac output factors
HR
Preload
Afterload
Contractility
HR and CO
Heart Rate: CO = HR X SV. Stroke volume = volume of blood pumped from LV per beat. When SV is stable, raising HR will raise CO proportionally (direct correlation)
Preload and CO
Preload: End-diastolic volume (EDV) = volume of blood in the ventricle at the end of diastole (the load of blood DELIVERED to the heart). The greater the preload, the greater the ventricles stretch, the greater strength of contraction and therefore the greater the stroke volume. Frank-Starling Law: when all other factors remain constant, the more EDV, the more SV.
Afterload and CO
Afterload: The load the heart contracts against to eject blood (RESISTANCE it overcomes to push blood into the aorta). blood pressure is the result of heart pumping pressure and arterial wall resistance. Ejection fraction: roughly 2/3rds blood ejected from ventricles per pump (67%). If afterload was increased, ejection fraction would DECREASE lowering SV.
High BP/afterload = lower EF and SV and vice versa.
Contractility and CO
refers to intrinsic strength of ventricle, independent of preload and afterload. Inotropic medication INCREASES contractility. This increases SV and vice versa for lowering.
What is Cardiac output?
The amount of blood pumped out by each ventricle in one minute
CO’s of both ventricles are equal
70ml stroke volume per beat = 5L/min (whole adult blood content)
This value can increase while exercising up to 5 fold
Brachial plexus terminal branches and innervation
Musculocutaneous - Skin of anterolateral forearm - Brachialis, biceps brachii, coracobrachialis
Axillary - skin of lateral portion of shoulder+upper arm - Deltoid and teres minor
Radial - Posterior aspect of lateral forearm and wrist+post. Arm - triceps brachii, brachioradialis, anconeus, extensor muscles of post. Arm and forearm
Median - skin of lateral 2/3rd of hand+tips of digits 1-4 - forearm flexors, thenar eminence, lumbricals of hand 1-2
Ulnar - skin of palm and medial hand+ digits 3-5 - hypothenar eminence, some forearm flexors, thumb adductor, lumbricals 3-4 and interosseous muscles
Sacral plexus nerves
'Some Irish People Came Traveling Quickly On Perfect Paper Planes Laughing Proudly': Superior gluteal nerve Inferior gluteal nerve Nerve to Piriformis muscle Common fibular division of sciatic nerve Tibial division of sciatic nerve Nerve to Quadratus femoris Nerve to Obturator internus Posterior cutaneous nerve of thigh Perforating cutaneous nerve Pudendal nerve Nerve to Levator ani Perineal branch of S4
Main sacral plexus branches (6Ps and SIPPS)
6Ps Nerve to Piriformis Posterior cutaneous nerve of thigh Perforating cutaneous nerve Pudendal nerve Perineal branch of the 4th sacral nerve Pelvic sphlancnic nerves Major branches SIPPS: S – Superior gluteal nerve (nerve to quadratus femoris/inferior gemellus may be associated here since they share nerve roots) I – Inferior gluteal nerve (nerve to obturator internus/superior gemellus may be associated here since they share nerve roots) P – Posterior cutaneous nerve of thigh P – Pudendal nerve S – Sciatic nerve
Brachial plexus outline
C5 and C6 roots join -
branch dorsal scapula nerve and contribute to long thoracic -
superior trunk branches subclavian and suprascapula nerves-
anterior superior division branch posterior superior nerve to join posterior middle division -
lateral cord branches lateral pectoral nerve - musculocutaneous nerve terminates branch contributes to median nerve with C8 and T1
C7 root contributes to long thoracic nerve - middle trunk no branches -
posterior middle division sends anterior middle branch to join anterior superior division and joined by posterior superior and inferior from superior and inferior divisions respectively -
posterior cord branches upper subscapular, thoracodorsal and lower subscapular nerves - radial nerve branches auxiliary
C8 and T1 join -
inferior trunk -
anterior inferior division branches posterior inferior branch to posterior middle division- medial cord branches medial brachial cutaneous, medial pectoral and medial anterior brachial cutaneous -
branch contribute to median nerve with C5 and 6 and terminates in ulnar nerve
MABP =
CO X Total Peripheral Resistance (TPR)
Brachial plexus roots and what they give rise too
C5+6 - dorsal scapular nerve, contribute to long thoracic, suprescapular nerve and nerve to subclavian, branch to join posterior trunk, lateral pectoral, branch to join median nerve, terminates as musculocutaneous
DLSSPLMM - dont leave small smelly pubes lying mindlessly marooned
C7 - contributes to long thoracic nerve, branch to join anterior trunk, upper and lower subscapular branches, thoracodorsal, axillary branch and terminates as radial nerve
TAULTAR - lets get married at T’AULTAR (northern accent)
C8+T1 - T1 first intercostal nerve, branch to join posterior trunk, medial pectorial, medial cutaneous branches to forearm(C8) and arm(T1), contributes to median nerve, terminates as ulnar nerve
IPMMMU - If peeing might make much urine
Compensatory mechanisms in HF
Activation of sympathetic system Activation of renin-angiotensin system Natriuretic peptides (BNP) Ventricular dilation Ventricular remodelling
Activation of SNS in HF
Improves ventricular function by increasing HR and myocardial contractility
Does this by constricting veins, increasing venous return (preload)
Also, leads to constriction of arteries, increasing BP, increasing afterload; reducing SV and therefore CO
Activation of renin system in HF
Fall in CO and increased sympathetic tone detected by decreased renal perfusion in kidneys leads to activation
Increases salt and water retention and increases venous pressure (preload) maintaining SV and CO
As this retention increases, peripheral and pulmonary congestion occurs (oedema and dyspnoea)
Angiotensin also leads to arteriolar constriction; increasing BP (afterload); decreasing SV and CO
Natriuretic peptides BNP in HF
Released from ventricles; diuretic, natriuretic, hypotensive hormones help reduce pre and afterload
But this is inadequate long term
Ventricular dilation in HF
Myocardial failure leads to reduced SV and increased blood remaining in ventricles after systole.
This stretches myocardial fibres and restores myocardial contraction
Once HF is established, heart is not able to compensate enough via this method
Causes peripheral and pulmonary oedema
Ventricular remodelling in HF
Hypertrophy; loss of myocytes and increases fibrosis
Progressive and irreversible contractile failure occurs from this
HF progression
heart failure begins with depressed ejection fraction (EF)
Begins after index event like MI, producing initial decline in pumping capacity
After this, compensatory mechanisms are activated
In the short term these systems restore CO and cardiac function to normal range and patient is asymptomatic
With sustained activation of these systems can lead to secondary end-organ damage within the ventricle, remodelling of LV occurs and subsequent cardiac decompensation. Patient becomes symptomatic
Upper and lower respiratory tract consists of..
Upper - nasal cavity, pharynx and larynx
Lower - trachea, primary bronchi and lungs
Chest/back surface landmarks for clinical relevance
Sternal angle, or Angle of Louis, is a palpable clinical landmark in surface anatomy.
Junction line of manubrium and body of the sternum.
2nd ribs attach the sternum at this level.
Trachea also bifurcates at this level/imaginary plate.
Apex of scapula:
7th ICS space usually
Apex of axilla:
Gently separate the arm from the thorax for a few cm. Push hand into axilla space can reach 2nd ICS
VAN bundles
ICS vein, artery and nerve (VAN) are found anterior to innermost ICS and posterior to Internal ICS directly inferior to superior rib in the intercostal groove
Clinical relevance; approach from upper margin to avoid VAN bundle, except in nerve block
Ribs and ICM
12 pairs:
7 true, 1-7; attach directly to the sternum
3 False, 8-10; attach to the rib above
2 floating, 11-12; only attached to the spine with no anterior attachment (protect the kidneys posteriorly)
Intercostal muscles:
Three layers; external, internal and innermost intercostal muscles
External: elevates ribs during forced inspiration
Internal: depresses ribs during forced expiration
Innermost: depresses ribs in forced expiration
Intercostals of each hemithorax act as one muscle: if one point is painful, then half the thorax will reduce movement
Lungs
Main functions:
Gaseous exchange
Anatomy:
Right lung divided into 3 lobes; left is 2
Trachea divides at the carina (at sternomanubrial junction) into right and left main bronchi. Right is steeper (clinical relevance to aspiration). Branch into secondary, tertiary bronchi, bronchioles then into terminal bronchioles and finally alveoli
Lungs enclosed with visceral and parietal pleura (join at hilum)
Interpleural space has small amount of lubricating fluid for movement
Alveolar pneumocytes - type I; 95-97% total surface area of lungs, where gaseous exchange occurs. Type II; secrete pulmonary surfactant and reabsorb sodium and water, preventing fluid buildup. Macrophages; remove pathogens in lungs.
Mucocillary clearance - Mucous membranes in our respiratory tract trap airborne pollutants and tiny cilia transport them to our pharynx, where they are swallowed or coughed out
Airways lined with ciliated columnar cells and goblet cells (mucus producing). Fewer goblet cells in smaller airways. Mucus traps macrophages, inhaled particles and bacteria and is moved by the cilia in cephalad direction
Dual blood supply: pulmonary artery (venous) and bronchial artery (arterial)
Bronchial artery from descending aorta along larger conducting airway carries oxygenated blood to lung tissue
Common lung pathologies
Haemothorax: blood between pleura
Pleural effusion: fluid build up between pleura
Pneumothorax: Air between pleural layers
Pyothorax/empyema: pus/infection within pleura
Vanishing tumour: fluid within fissures of lungs
During PE: occlusion to branch of pulmonary artery NOT bronchial
Hemorrhagic necrosis: alveolar spaces filled with blood; shows opacity/consolidation in CXR
Pleuritis: severe pain; changes with breathing
Pleuritic chest pain - pain aggravated with breathing
mechanism of inspiration
Inspiration - active:
Diaphragm descends (innervated by phrenic nerve C4-5 keeps the thorax alive!)
ICS move ribs upwards and outwards
Volume of thorax increases
Increases negative pressure in thorax and therefore alveoli
Suction of air through trachea and bronchi into lung parenchyma
Gaseous exchange
During REST:
75% respiration is abdominal (diaphragm)
25% thoracic (external ICS)
mechanism of expiration
Expiration - passive
Elastic recoil
Diaphragm returns
ICS relax and ribs move down and inwards
Pressure becomes more positive
Air forced out of thorax and airway
During EXERCISE or respiratory distress:
Accessory muscles are recruited during inspiration - sternomastoids, scalenes etc.
Ventilation increases and expiration becomes active
Expiration causes contraction of abdominal wall and internal ICS
Also active during cough reflex
Granulomatous disease in the lung
Tubercle in the lung/Granuloma in the body, is an organized collection of macrophages and is a special defensive cell arrangement.
Granulomas form when the immune system attempts to wall off substances, it perceives
as foreign, but is unable to eliminate.
Such substances include infectious organisms including bacteria (MTb etc.), fungi, foreign bodies (suture fragments etc.)
In TB, macrophages often fuse to form multinucleated giant cells (Langhans giant cell).
Granulomatous disease causes
Microorganisms Tuberculosis Leprosy Schistosomiasis Histoplasmosis Cryptococcosis Cat-scratch disease (Bartonella henselae) Listeria monocytogenes Leishmania spp. Pneumocystis pneumonia Unknown/Auto-immune Rheumatic Fever Sarcoidosis Crohn's disease Rheumatoid arthritis Granulomas associated with vasculitis FB Foreign-body granuloma Aspiration pneumonia (food particles, pill fragments, …)
anterolateral abdominal muscles
From deep to superficial:
Originate from thoracolumbar fascia, anterior iliac crest and external surfaces of ribs and costal cartilages.
Insert in forming rectus sheath surrounding the rectus abdominis muscle.
Innervated by thoraco-abdominal nerves.
Transversus abdominis: fan like array of muscle extending transversely. Innervated by T6-12 anterior rami and first lumbar nerve.
Internal oblique: hands to boobs direction, innervated by anterior rami T6-12 spinal nerves and first lumbar nerve
External oblique: hands in pockets arrangement. Innervation T7-11 and subcostal nerve. Free border forms inguinal ligament between the ASIS and pubic tubercle
Rectus abdominis: arises from pubic symphysis and pubic crest and inserts into the xiphoid process and 5-7th costal cartilages. Innervated by anterior rami T6-12.
80% people have and insignificant muscle called pyramidalis (located anterior to inferior rectus abdominis) origin pubic crest to the linea Alba. Draws down on the linea alba.
Arteries and origin of anterolateral abdominal wall
Musculophrenic (descends along costal margin supplies diaphragm) and superior epigastric (descends in rectus sheath supplies ab wall) from the internal thoracic artery
10 and 11th posterior ICA and subcostal arteries from the aorta (supply lateral abdominal wall)
Inferior epigastric and deep circumflex from the external iliac artery (deep abdominal wall)
Superficial circumflex and superficial epigastric from the femoral artery (superficial abdominal wall)
Inguinal canal contents and structure
Males: spermatic cord
Females: uterine ligament
Both: blood and lymphatics, ilio-inguinal nerve, genital branch of the genitofemoral nerve
Has a deep and superficial inguinal ring (openings where the cord enters and exits the abdominal fasciae)
GI tract in order
Oral cavity Pharynx Oesophagus (T10 crosses diaphragm) Stomach Small intestine: duodenum, jejunum and ileum Large intestine/colon: Cecum (with/without appendix), ascending, transverse, descending, sigmoid Rectum Anal canal
Quadrant division of abdomen and contents
Right upper: liver, gallbladder (posteriorly)
Right lower: large and small colon, cecum and appendix
Left upper: spleen, stomach, pancreas (posterior to stomach) flexure of transverse colon and top of descending colon
Left lower: large colon and small intestine
Pelvic region: sigmoid colon, rectum, uterus (female), anal canal, perineum
Main arteries of arm and hand
Origin from brachiocephalic which splits into common carotid and subclavian (on the right side) and directly from the arch of the aorta on the left side (left subclavian)
Becomes the axillary passing underneath clavicle with the superior thoracic, thoraco-acromial, lateral thoracic, subscapular and anterior/ posterior circumflex humeral arteries branching from it
Becomes brachial artery around humeral neck level branching the profunda brachii, superior and inferior ulnar collaterals
At the cubital fossa splits into the ulnar (medial) and radius (lateral) artery
Radial artery has a radial recurrent branch and ulnar has a posterior and anterior recurrent branch
Both are connected by common interosseous artery just under cubital fossa level
At the wrist the arteries become the deep and superficial palmar arches which then extend to become the common palmar digital artery (fingers and thumb)
Veins of the arm and hand
All deep venous networks follow the same name structure as the arteries of the hands and arms
Superficial:
Hands: dorsal digital network collect venous blood in the hand
At the wrist posteriorly are the basilic and cephalic (superficial) veins. These travel and move anteriorly throughout the forearm.
Anteriorly the median vein of the forearm travels up from the wrist and joins the cephalic at the ante cubital fossa.
The median cubital vein connects the basilic to the cephalic at the cubital fossa level
These veins are the most common venous puncture sites: median cubital, basilic, cephalic, brachial (deep)
In the arm the basilic and cephalic vein travel anteriorly either side of the deep brachial vein and the basilic joins the brachial forming the axillary vein travelling under the clavicle
The cephalic also joins the axillary near the coracoid process of the scapula
The axillary becomes the subclavian and the subclavian is joined by the internal and external jugular veins to form the brachiocephalic vein leaving the arm
Arteries of the leg
Abdominal aorta splits at L4 (aortic bifurcation) into the right and left common iliac vessels
These split into the internal iliac and external iliac vessels
Internal iliac (more internal) branches the obturator, superior and inferior gluteal vessels supplying the obturator externus, pectineus, adductors, gracilis and muscles attached to ischia tuberosity.
External iliac branches the inferior gastric which travels on the anterior iliac fossa.
External iliac becomes the femoral artery at level of inguinal ligament. Femoral artery travels down to the knee from anterior crossing to posterior via the adductor hiatus
Branches the profunda femoris (with perforating branches) which pass through the adductor Magnus, supplying the medial, lateral and posterior parts of the anterior thigh.
Profunda femoris branches the medial (supply the head and neck of femur and anastomoses with inferior gluteal artery) and lateral (supplies anterior gluteal region and joins genicular peri-articular anastomoses via the descending branch) circumflex branches
At the popliteal fossa the femoral artery becomes the popliteal which splits into the anterior and posterior tibial arteries
Anterior travels down the anterior tibia becoming the dorsalis pedis at the ankle level
Branches the arcuate artery and all terminates in dorsal metatarsal and dorsal digital arteries
Posterior tibial travels posteromedially branching the fibular artery. Splits into the medial and lateral plantar arteries on sole of foot, joined by the plantar arch artery. Then branches into plantar metatarsal then plantar digital arteries to terminate
Thoracic aorta branches
Descending thoracic aorta - Boys May Only Pinch Silly Inane Substances: Bronchial Mediastinal Esophageal Pericardial Superior phrenic Intercostal and Subcostal arteries
Abdominal aorta branches
Abdominal aorta - Inside Cold Supermarkets Really Get Icy Liquids: Inferior phrenic (T12; PAIRED) Coeliac artery (T12) Superior Mesenteric artery (L1) Renal arteries (L1-2 PAIRED) Gonadal arteries (L2 PAIRED) Inferior Mesenteric artery (L4) Lumbar arteries (L1-4 TWO PAIRS)
Shoulder joints
Acromioclavicular - gliding Joint less movement than others
Scapulothoracic
Sternoclavicular - physically a saddle joint but functionally a ball and socket joint
Glenohumeral - ball and socket
Glenohumoral joint
Ball and socket synovial joint
Lax capsule to allow movement - very weak capsule hangs dependent underneath joint therefore making it very unstable
Most common dislocation in body however only affects 1-2% of population
Head of humerus is 3-4x larger than the glenoid fossa therefore it doesn’t sit in the joint entirely also making it unstable
Stability of the joint comes from the rotator cuff muscles and ligaments
Glenoid labrum helps deepen glenoid cavity by 2.5mm however is prone to damage from dislocations or from age etc. Causing tears or detachment. Also acts as anchoring point for ligaments
Subscapular bursa - can also get bursa infraspinatus but not common.
Blood supply from suprascapular, subscapular, anterior and posterior circumflex humeral arteries
Innervated by axillary, suprascapular, lateral pectoral nerves
Factors affecting glenohumeral stability
Glenoid fossa and humeral head mismatch size
Glenoid labrum helps deepen cavity 2.5mm. Acts as chock block and attachment site for ligaments and long head of biceps. 20% of joint compression effect.
Glenohumeral, coracoacromial and corcacohueral ligaments help stabilise
Intra articular pressure - negative pressure creates suction between bones holding joint together. If pressure is dissipated dislocation very likely
Muscles - rotator cuff (supraspinatus for abduction, teres minor, infraspinatus and subscapularis), long head of biceps and deltoid very important
Ligaments of the glenohumeral joint
Superior, middle and inferior glenohumeral ligaments extend from the scapula to the head of the humerus
Superior - supraglenoid tubercle to lesser tuberosity blends with coracohumeral ligament to close the rotator interval
Middle - labrum or bony glenoid neck to medial to lesser tuberosity inferior to subscapularis tendon, often stretched by heavy lifting
Inferior - hammock shaped important for arm abduction to cup head.
Between the superior and middle protrudes the supscapular bursa
Long head of biceps femoris is continuous with the glenoid labrum
Coracohumeral ligament goes from the coracoid process to the humerus
Transverse ligament runs above the glenohumeral ligaments over the long head of biceps attachment
Stability of shoulder from muscles
Primary - rotator cuff muscles (supraspinatus, infraspinatus, subscapular and teres minor), Deltoid and long head of biceps
Secondary - teres major, latissimus dorsi, pectoralis major
The cuff muscles actively resist deltoid shear forces - the glenohumeral joint compression centres the humeral head making more stable
Rotator cuff tendons blend into the capsule - cuff tension actively tightens glenohumeral ligaments
Proprioceotion - joint position awareness and repositioning through continuous afferent input and efferent output
Ligaments of the spine
Ligamentum flavum - runs between one vertebrate to another in the foramen
Interspinous ligament - runs over the superior and inferior articulating processes
Intertransverse ligaments - between transverse processes of superior and inferior vertebrae
Posterior longitudinal ligament - runs whole length of spine inside foramen anterior to ligamentum flavum
Anterior longitudinal ligament - runs whole length of spine on anterior body of vertebrae
Supraspinous ligament - runs length of whole spine on spiney processes
Coeliac artery branches
Branches off aorta at level of T12, splits into three: left gastric, common hepatic and splenic artery.
Left gastric artery branches off to supply the lesser stomach (also gives of oesophageal branch) and anastomoses with the right gastric artery
Splenic artery gives off the posterior gastric artery then supplies the spleen and gives off the left gastroepiploic branch supplying greater stomach
Common hepatic artery divides into the hepatic artery proper, gastroduodenal (which gives off the right gastroepiploic branch to the greater stomach and the pancreatic-duodenal superior artery) and supra duodenal artery. These supply the stomach, pancreas, first part of duodenum and distal bile duct.
the hepatic artery proper splits into right and left branches. the right gives off the cystic branch which supplies the gallbladder and cystic duct.
Superior mesenteric branches
Branches off the aorta at level of L1
Gives off the pancreatic-duodenal inferior branch which anastomoses with the superior branch from the gastroduodenal artery (origin common hepatic) to supply the pancreas and duodenum
Gives off the middle, right and iliocolic arteries which all supply the large intestine as well as several other branches to the small intestine. All these anastomose together the mesentery fascia
Inferior mesenteric artery
Branches off aorta at level L4
Gives rise to left colic artery (supply colon), which in turn gives rise to sigmoid branch supplying the sigmoid colon
Later the inferior mesenteric artery splits into the sigmoid branch and superior rectal. The sigmoid anastomoses with the other sigmoid branches to supply the colon while the superior rectal supplies the rectum
Azygos vein system/chest wall drainage
The first left and right ICV drain the first ICS directly into the brachiocephalic veins
The right and left 2nd and 3rd ICV drain into the superior ICV
The left superior ICV joins the left brachiocephalic while the right superior ICV joins the azygos vein.
The 4-7th left ICV joint the accessory hemiazygos vein (crosses the vertebrae at T6 to join the azygos
The 8-12th left ICV join the hemiazygos vein (arises from ascending lumbar vein), crossing over around T7 to join the azygos
All ICV after the 3rd on the right side drain into the azygos vein directly
The azygos arises from the IVC, passes through the aortic hiatus (T12) and drains into the SVC at the 2nd ICS level posteriorly.
Hepatic portal drainage system
Begins at capillaries of the GIT, gallbladder, pancreas and spleen. Tributary veins drain these organs directly into the hepatic portal vein branches in the liver, delivering blood to the sinusoids for digestion/processing of carbohydrates, amino acids, lipids, vitamins and iron. These molecules are stored or distributed around the body or degraded and excreted via the kidneys.
The hepatic vein then travels from the liver to the IVC, joining just underneath the diaphragm to bring the blood back to the heart and therefore redistribute any molecules put back in via the sinusoids
Describe the abdominal peritoneum
A serial membrane of the abdominal cavity
Peritoneum attached to the organs is termed visceral, while that attached to the body wall is termed parietal. The space in-between (peritoneal cavity) has a small amount of serous fluid to lubricate movements or organs.
Organs that have migrated away from the body wall during development are suspended within the peritoneum, and these developments create folds of the peritoneum onto itself within the abdominal cavity, called the greater and lesser omentum (the lesser sits above the stomach, and the greater covering the large and small intestines)
The peritoneum suspending the large and small intestines is termed the mesentery, and contains all vessels supplying all of the organ.
All innervation comes retroperitoneal from the spinal nerves, and travels to intraperitoneal organs via the mesentery
Retroperitoneal organs
SAD PUCKER
Supradrenal glands Aorta/IVC Duodenum (first 2/3) Pancreas Ureters Colon (ascending and descending) Kidneys (E)Oesophagus Rectum
Surface landmarks of the abdomen
Linea alba
Umbilicus
Semilunar lines (bilaterally either side linea alba borders rectus sheath)
ASIS
Pubic symphysis
Inguinal grooves (V lines where inguinal ligament would run internally)
Abdominal regional divisions of reference
Divided into 9 segments by the midclavicular (sagittal) plane, subcostal and transtubercular (transverse) lines
Superiorly consists of the right and left hypochondrium regions and the epigastric region (centre division)
Middle row consist of the umbilical (centre) region and the right and left lateral regions
Inferior row consists of the right and left inguinal regions and the pubic (hypogastrium) region in the centre.
The division of these helps to localise pain during diagnosis to help determine which organ is causing said pain.
Mcburneys point
Used to help diagnose appendicitis
1/3rd away from the ASIS (between the ASIS and the umbilicus) is McBurneys point. Palpating this area in patients with appendicitis can cause significant pain
Dermatomes of the abdomen and referred pain
Referred pain is sent to the area of the skin that the corresponding nerve supplies, instead of the organ itself as this is what the brain is most used to receiving so can feel like the pain is elsewhere when it is in fact the organ sending pain signals.
The diaphragm is supplied by C4 and referred pain is often in the anterior shoulder
Oesophagus supplied by T4/5 often pain is felt in the centre of the thorax between the nipples
T6 extends across just under the nipple line
T7 runs straight across
T8 supplies the stomach, liver and gall bladder - referred pain for the stomach sits roughly on skin anterior to the stomach itself
T10 and 11 also supply the liver and gall bladder, extending across the abdomen along the umbilicus line - referred pain sent to umbilicus area
T10 supplies the small intestine - referred pain sent to umbilicus area
T11 the large intestine - referred pain sent to just underneath the umbilicus area
T10-L1 supplies the kidneys and testes and referred pain is found along the inguinal groove regions
T11-L1 supplies the urinary bladder and referred pain is around the pubic symphysis
Primary functions of the GIT
Absorption Secretion Storage Motility Digestion
Phases of digestion overview
Cephalic: chemoreceptors and mechanoreceptors in the nasal and oral cavity are stimulated by tasting, chewing, swallowing, smelling food or eating, engaging primary neuronal responses. Mainly mediated by Vagal nerve (cranial nerve 10)
Gastric phase: begins when food enters the stomach and is linked to stomach distension and contents (amino acids and peptides) engaging neuronal and hormonal responses (local nervous secretory responses, vagal reflexes and gastrin-histamine stimulation)
Intestinal phase: left stomach enters the intestines, involves intestinal contents (proteins, fats, H+ ions) engaging primarily hormonal but also paracrine and neuronal responses. (hormones and neural response)
PNS and SNS actions in GIT
PNS: mediated via vagal nerve and acetylcholine increase secretions increase motility decrease sphincter constriction increase blood flow
SNS: mediated via thoracolumbar nerves decreased sections decreased motility increase sphincter contractions decreased blood flow
Neural signalling molecules in the GIT and function
Acetylcholine: Released from PNS. Acts on glands, smooth muscle and blood vessels. Increases secretions, motility and blood flow.
ATP: released by SNS. Act on blood vessels to decrease blood flow (construction)
Calcitonin-gene related peptide (CGRP): released from afferent sensory nerve, act on blood vessels to increase blood flow
Enkephalins. released from the enteric nervous system. Act on smooth muscle to constrict sphincters.
GRP: released from PNS and ENS. Act on glands to increase gastrin secretions (increases H+ ions)
Norepinephrine: released from SNS acts on glands, smooth muscle and blood vessels to decrease motility, secretion and blood flow
Neuropeptide Y: released from ENS and SNS. Acts on smooth muscle to decrease motility
Substance P: released from Afferents and PNS. Acts on blood vessels and glands to increase blood flow.
Vasoactive intestinal peptide: released by glands, acts on smooth muscle, blood vessels to increase motility and blood flow.
GIT primary hormones and actions
Cholecystokinin (CCK): released by I cells throughout the small intestine (tapering off in the ileum). Acts on the exocrine pancreas, gallbladder and stomach. Acts to increase enzyme secretion, increase gallbladder contraction and decreases gastric emptying.
Gastrin: released from G cells in the antrum of the stomach, duodenum and tapering off in the jejunum. Acts on the stomach to increase acid secretion.
Glucose insulin peptide (GIP) released from K cells in the duodenum and jejunum. Acts on the stomach and endocrine pancreas to inhibit acid secretion and release insulin
Motilin: released from M cells in the duodenum and jejunum. Acts on smooth muscle to increase contractions and MMC
Secretin: released from S cells throughout the small intestines (tapering off in the ileum). Acts on the pancreas and stomach. Increases bicarbonate and pepsin secretion
Paracrine signalling molecules in GIT
Histamine: released from enterochromaffin-like cells and mast cells. Act on the stomach to increase acid secretion
Nitric oxide: released from numerous cell types acting on smooth muscle, blood vessels to relax smooth muscle and increase blood flow
Prostaglandins: from numerous sources. Acts on gut mucosa to increase mucous and bicarbonate secretion
Somatostatin: released from D cells. Acts on the stomach and pancreas to inhibit secretion.
Small intestine gross anatomy overview
A highly convoluted thin walled tube
The duodenum (1st part) is suspended by the lesser omentum
The 2nd/descending and 3rd/horizontal parts are retroperitoneal
The 4th/ascending part emerges anteriorly in the common mesentery suspended by the smooth muscle at the duo jejunum junction
The jejunum is suspended in the common mesentery as is the ileum. The blood vessels travel in this mesentery to supply the tissues
Cellular anatomy of the small intestine
In the duodenum the submucosal glands of Brunner secrete bicarbonate containing mucus to neutralise HCL entering from the stomach
The luminal surface (especially the jejunum) consists of circumferential (ring like) folds called plicae circulares composed of mucosal and submucosal tissue
Mucosal surface is filled with villi and deep tubular glands (crypts) lined by simple columnar goblet cells for secretion and absorption. They produce a watery medium promoting uptake of minerals and nutrients
Enter-endocrine cells secrete hormones such as CCK and secretin to encourage glandular secretion
Paneth cells secrete lysosomes into the crypts for digestive enzymes to destroy bacterial cells
The vascular lamina propria supports the lacteal (blood vessel)
The submucosa supports Large blood and lymph vessels and cell bodies/axons of the parasympathetic neurons
Peyers patches are found in the submucosal and lamina propria and are masses of lymphoid nodules mostly located within the ileum
Specialised M cells at the epithelium-lymphoid nodule interface play a role in taking antigen to immune reactive lymphocytes, also located in the ileum
Important anatomical levels
C3 - hyoid bone
C4 - thyroid cartilage
C6 - beginning of trachea and oesophagus
T4 - aortic arch and sternal angle of Louis
T8 - IVC hiatus
T10 - oesophageal hiatus
T12 - aortic hiatus
L1 - transpyloric plane (fundus gallbladder, neck of pancreas)
L4 - iliac crest and aortic bifurcation
Constituent and accessory elements of the GIT
Constituent: Mouth Larger part of the pharynx Gullet (esophagus) Stomach Small intestine Colon
The accessory digestive organs include:
Teeth Tongue Salivary glands Liver Gall bladder Pancreas
Enteric nervous system of the GIT
‘brain of the GIT’
Has around 100 million neurons, extending from oesophagus to anus. Can operate independently of the ANS but still subject to regulation via neuronal control.
The Auerbach’s plexus/plexus myentericus and the Meissner plexus/plexus submucosus constitute the nervous system of the intestinal wall
The Auerbach’s plexus controls the motility of the GIT as well as frequency and strength of muscle contractions. Motor neurons of the plexi supply the longitudinal and circular muscle layers of the muscularis
The messier plexus innervates the secreting cells of the mucosa epithelium via motor neurons so controls GI secretion
Swallowing process
Swallowing occurs in 3 stages:
Voluntary phase
Pharyngeal phase
Esophageal phase
Voluntary phase begins with the bolus of food being moved up and down by the tongue and forced against the palate in the posterior oral cavity and the oropharynx
The involuntary phase begins with the entry of the bolus into the oropharynx. Receptors are stimulated and transmit to the medulla and lower pons. Inducing the upward movement of the soft palate and uvula and to close the nasopharynx preventing more food being swallowed. The epiglottis closes the laryngeal opening also preventing it enter the respiratory system. Once the oesophageal sphincter is relaxed the food bolus enters the oesophagus
The oesophageal phase begins when the bolus enters the oesophagus. Peristalsis propels the bolus pushing it to the stomach. When the lower oesophageal sphincter relaxes it can then go into the stomach.
Stomach physiology
Once food reaches the stomach, mixing waves occur every 15-a 25 seconds. Food is macerated (soaked and softened) and converted to chyme by the gastric gland secretions.
Mixing waves increase in strength when chyme nears the pyloris. This is followed by gastric emptying and the chyme enters the duodenum as each mixing wave periodically pushes small bits of chyme out via the pyloric sphincter. The remaining amount is pushed back into the corpus of the stomach, constantly back and forth to ensure good mixing.
The food will have emptied from the stomach within a few hours from intake. Carbs spend the least time there while food with high protein content remains longer, fatty food remains longest.
Only a small amount of food is absorbed (water and certain medications like aspirin, and alcohol) here since the epithelial cells are impermeable to most substances.
Stomach enzymes physiology
Salivary amylase is inactivated once chyme mixes with gastric acid. Tongue lipase is activated which degrades triglycerides into fatty acids and diglycerides.
Microbes taken in with food are killed by the high acidity, proteins are also partially denatured by the Hydrochloric acid (secreted by parietal cells). But the Hcl stimulates secretion of hormones promoting flow of bile and pancreatic juice.
Pepsin is active in acidic environments and digests proteins. To prevent digestion of proteins in the stomach wall it is secreted in its inactive form pepsinogen and is activated by Hcl.
Parietal cells are also needed for Vit B12 absorption
Gastric lipase cleaves triglycerides into fatty acids
Pancreatic lipase is also a significant digestion enzyme
Composition of pancreatic juice
Every day, the pancreas produces about 1200–1500 mL of pancreatic juice, characterized by clear, colorless fluid.
It mainly consists of water, a little salt, sodium carbonate, and a few enzymes.
Sodium carbonate in the pancreatic juice increases the alkaline pH value slightly, which activates the digestive enzymes in the small intestine:
Consists of the head, neck, body and tail
Mostly formed of acinar sac-like exocrine glands that secrete enzymes and sodium bicarbonate
It is secreted into tributaries of the pancreatic duct and then the duodenum via the ampulla sphincter
Trypsin cleaves proteins into amino acids, lipase digests fats and amylase helps digest carbohydrates
Pancreatic secretion is regulated by CCK and secretin primarily, as well as ACh from the vagal nerves
The biliary system
Consists of ducts transporting bile from the liver cells to the gallbladder and second part of the duodenum
Bile if formed within the liver hepatocytes (consists largely of water, bile and pigments from spleen and RBC breakdown)
It is then discharged into the surrounding bile canaliculi, which then merge into bile ductules that converge with intrahepatic branches of the portal vein and hepatic artery
Bile is brought out of the liver by the right and left bile ducts, merge at the porta hepatis, to form the common hepatic duct
The duct is joined by the cystic duct (from the gallbladder) to form the bile duct
Joins with the pancreatic duct forming the ampulla of Vater in the wall of the second part of the duodenum
Small intestine (duodenum) physiology
Chyme enters the duodenum. This stimulates the intestinal mucosa to produces secretin and cholecystokinin pancreozymin (CCK).
CCK triggers the release of pancreatic enzymes into the bloodstream, ensuring rhythmic contraction of the gall bladder and stimulation of bile secretion to be released via the bile duct
The papilla of Vater is in the middle of the duodenum and is the point where the junction of bile and pancreatic ducts enter
Further digestive enzymes are released from both to process the acidic chyme.
At the same time the chyme is also neutralised via alkaline secretions of the duodenum.
Food absorption of the small intestine
90% of food absorption occurs via diffusion, osmosis and active transport.
10% occurs in the stomach and colon
All monosaccharides are transported via facilitated diffusion or active transport. Faeces only contains indigestible cellulose and fibres.
Fructose is transported via facilitated diffusion while glucose and galactose via secondary active transport (Na+ gradient needed)
Most proteins use active transport mainly in the duodenum and jejunum
Some amino acids need Na+ dependent transport similar to glucose
Di and tripe-tides need at least a symporter (Na+) to enter cells for hydrolysis to single amino acids
Dietary fats use simple diffusion once digested enough.
Bile salts facilitate formation of micelles which can transport lipids and lipid soluble vitamins (A, D, E and K) and cholesterol
Bile salts are reabsorbed within the ileum and returned to the liver via the hepatic portal system
Dermatomes of the head
A dermatome is an area of skin supplied by a single spinal nerve.
Dermatomes of the head are supplied by branches V1, V2 and V3 of the trigeminal nerve: Trigeminal nerve (CN V)
V1: ophthalmic branch – the lateral aspect of the forehead
V2: maxillary branch – the cheek
V3: mandibular branch – the lower jaw (avoid the angle of the mandible as it is supplied by C2/C3)
Other
C2: 1-2 cm lateral to the occipital protuberance
C3: the supraclavicular fossa in the midclavicular line.
Dermatomes of the upper limb
C4: over the acromioclavicular joint.
C5: the lateral aspect of the lower edge of the deltoid muscle (known as the “regimental badge”).
C6: the palmar side of the thumb.
C7: the palmar side of the middle finger.
C8: the palmar side of the little finger.
T1: the medial aspect antecubital fossa, proximal to the medial epicondyle of the humerus.
Dermatomes of the torso
T2: the apex of the axilla.
T3: the intersection of the midclavicular line and third intercostal space.
T4: the intersection of the midclavicular line and the fourth intercostal space at the level of the nipples.
T5: the intersection of the midclavicular line and the fifth intercostal space, horizontally located midway between the level of the nipples and the level of the xiphoid process.
T6: the intersection of the midclavicular line and the horizontal level of the xiphoid process.
T7: the intersection of the midclavicular line and the horizontal level at one quarter the distance between the level of the xiphoid process and the level of the umbilicus.
T8: the intersection of the midclavicular line and the horizontal level at one half the distance between the level of the xiphoid process and the level of the umbilicus.
T9: the intersection of the midclavicular line and the horizontal level at three-quarters of the distance between the level of the xiphoid process and the level of the umbilicus.
T10: the intersection of the midclavicular line, at the horizontal level of the umbilicus.
T11: the intersection of the midclavicular line, at the horizontal level midway between the level of the umbilicus and the inguinal ligament.
T12: the intersection of the midclavicular line and the midpoint of the inguinal ligament.
Dermatomes of the lower limb
L1: the inguinal region and the very top of the medial thigh.
L2: the middle and lateral aspect of the anterior thigh.
L3: the medial epicondyle of the femur.
L4: the medial malleolus.
L5: the dorsum of the foot at the third metatarsophalangeal joint.
S1: the lateral aspect of the calcaneus.
S2: at the midpoint of the popliteal fossa.
S3: at the horizontal gluteal crease (the horizontal crease formed by the inferior aspect of the buttocks and the posterior upper thigh).
S4/5: the perianal area.
Myotomes and important myotomes
A group of muscles innervated by a single spinal nerve.
C4: shoulder shrugs C5: shoulder abduction and external rotation; elbow flexion C6: wrist extension C7: elbow extension and wrist flexion C8: thumb extension and finger flexion T1: finger abduction L2: hip flexion L3: knee extension L4: ankle dorsiflexion L5: big toe extension S1: ankle plantarflexion S4: bladder and rectum motor supply
Plexuses and general innervations
Cervical plexus (C1 – C4): innervates the diaphragm, shoulders and neck.
Brachial plexus (C5 – T1): innervates the upper limbs.
Lumbosacral plexus (L2 – S1): innervates the lower extremities.
Colon functions
Completion of resorption
Formation of certain vitamins
Formation of feces
Excretion of stools from the body
Colon physiology
Chyme from the ileum is regulated by the ileocecal sphincter. Peristalsis is increased post meal by the stomach-ileum reflex, transporting the chyme into the cecum. This movement across the sphincter stimulates the colon to produce austral contractions and peristalsis.
No enzymes are secreted, all digestion here is carried out by bacteria. Several vitamins (B and K included) are absorbed here.
The glands of the mucosal wall only secrete mucus to lubricate the bolus.
Chyme remains in the colon for approx. 3-10 hours before it becomes solid or semi-solid due to water absorption by the colon. The resulting stool is made of excess water, inorganic salts, GI epithelial cells, bacteria, products of bacterial metabolism or indigestible food parts.
The exocrine pancreas function and enzymes
Produces 1.5–2 liters of fluid that contains enzymes that help to break down carbohydrates and fats, proteolytic proenzymes (preliminary stages of enzymes), and bicarbonate.
Aids in meal digestion through the merocrine secretions that it produces. Malnutrition and malabsorption result without the exocrine pancreas.
Bicarbonate creates an alkaline pH (7.8-8) and also helps neutralise the acidity in the duodenum via secretion through the ductus pancreaticus.
Enzymes produced:
Trypsinogen and chymotrypsinogen Procarboxypeptidase Proelastase Lipase Cholesterinesterase enzyme α-amylase Ribonuclease and deoxyribonuclease
Function and activation of trypsin in the gut
The duodenal cuticular layer and the Brunner’s glands secrete the enzyme enterokinase that transforms trypsinogen into trypsin. Trypsin transforms all of the other pancreatic proenzymes into their active forms
ANS neuron comparison
PNS ganglion are located in the peripheries, neurotransmitters tend to only be ACh to muscarinic receptors
SNS located adjacent to the spine (short pre-ganglionic neuronal and long post-ganglionic) neurotransmitters tend to be noradrenaline to alpha or beta receptors but can be ACh to muscarinic receptors
Spinal nerves
31 pairs 8 cervical - all arise above the corresponding vertebrae aside from C8 which comes from below. all other nerves arise from below after this. 12 thoracic 5 lumbar 5 sacral 1 Coccygeal
Grey and white matter in the brain and CNS
Brain: white matter in the middle grey In the peripheries
Spinal chord: white matter in peripheries and grey in the centre
Ratio of the grey to white is low in the cervical section and increases inferiorly (gets bigger going down the spine into thoracic, lumbar, sacral etc)
Ratio is high in sacral bodies (lots more axon tracks joining the spinal cord so lots more myelinated axons)
Grey matter: is divided into ‘horns’ which have a functional division:
- dorsal horn receives sensory input
- ventral horn houses alpha and gamma motor neurons
- There is an intermediate horn in T1 - L2/3 which houses visceral motor output (sympathetics relay here)
How to orientate yourself with the clavicle
Superiorly should be very smooth while inferiorly is not due to ligament articulations and subclavian groove (attachment for subclavius). Then to orientate left or right: find smooth smaller end that articulates with the sternum and other larger end is acromial end
Movements of the upper limb and joints
Sternoclavicular: elevation and depression and protraction (forward) and retraction (back)
Glenohumoral: extension, flexion, adduction and abduction, internal (medial) and external (lateral)
Elbow: flexion, extension, supination, pronation,
Wrist: flexion, extension
Fingers: flexion, extension, finger adduction and abduction
Axial and appendicular skeleton
Axial: supportive structure of the body. Includes the skull, vertebrae, sternum, ribs and hyoid bone
Appendicular: Makes possible a considerable degree of movement in the body. Includes the pictorial and pelvic girdles, upper and lower limbs
Classification of bones
Long bones: Clearly long and have a medullary cavity, hollow diaphysis of compact bone and at least 2 epiphyses eg femur or phalanx
Short: are cuboid shaped, predominantly cancellous bone with thin cortex of compact bone with no cavity. eg carpal or tarsal bones
Flat: generally more flat than round eg cranial or ribs
Irregular: Have more than two shapes within them such as scapulae or vertebrae
Sesamoid: developed in tendons, often mixed with fibrous tissue and have a cartilaginous articular surface facing an articular surface of an adjacent bone. May be part of a synovial joint, generally pea sized (pisiform) the largest being the patella. They resist friction and compression, enhance joint movement (fulcrum for joint) and may assist local circulation
Joint classifications
Immovable/synarthroses
Partly moveable/amphiarthroses
Freely moveable/diarthroses
FIBROUS joints are connected by fibrous tissue eg sutures of the skull and are immovable.
Syndesmoses are partly moveable fibrous joints such as interosseous ligaments between the bones of the forearm and leg
Cartilaginous joints (synchondroses): essentially immovable and are seen during growth such as epiphyseal plates
Fibrocartilaginous joints are partially moveable eg intervertebral discs
Symphyses are also partly moveable fibrocartilaginous joints such as the pubic bones and manubrium and body of the sternum.
Synovial joints (diarthroses) are freely moveable. They are capped with articular cartilage and enclosed by fibrous joint capsule lined by synovial membrane with internal synovial fluid lubricating it
Joint movement classifications
Ball and socket: hip and shoulder: allows flexion, extension, adduction, abduction, internal and external rotation and circumduction
Hinge: ankle, interphalangeal joints: flexion and extension only one plane of movement
Saddle joint: carpometacarpal joint at thumb base: permits all actions but rotation
Ellipsoid: radoiocarpal joints: reduced ball and socket joint with reduced rotation able
Pivot joint: C1 and C2 vertebrae: allows pivot movement
Gliding joints: acromioclavicular, inter carpal, inter tarsal joints: allows sliding small motions in all directions without rotation. Have flat articulating surfaces
Difference between small intestine components
The duodenum and jejunum are roughly similar in wall structure, the main differences between these two and ileum is the duodenum and jejunum have fewer peyer’s patches (lymphoid nodules) than the ileum, but have many more villi folds within the wall*
Ileus has shorter villi, M cells are present and lymphoid aggregates forming follicles (Peyer’s patches) that extend throughout the lamina propria and submucosa
Sphincter of Oddi
refers to the smooth muscle that surrounds the end portion of the common bile duct and pancreatic duct. This muscle relaxes during a meal to allow bile and pancreatic juice to flow into the intestine.
The gallbladder
Serves as a storage chamber for bile discharged from the liver
Bile is concentrated here
The walls have multiple microvilli on luminal surfaces of the simple columnar epithelial cells that absorb water from the dilute bile
When the duodenum releases CCK in response to fat this stimulates the contraction of the gallbladder to discharge its contents into the cystic duct via peristaltic contractions
Oesophageal anatomy
Muscular tube 23-25cm long connects the pharynx to the stomach
Passes through the diaphragm at oesophageal hiatus (T10)
Has rich lymphatic system in submucosa
Three parts: cervical, thoracic and abdominal
Lining of lumen is stratified squamous epithelium
Part of the foregut, has three layers but no mucosa: important in cancer spread, bacterial spread after perforation etc.
Located in mediastinum
Three natural narrow points: upper oesophageal sphincter (anatomical sphincter, cricopharyngeus muscle), middle where aorta/left bronchus pass anteriorly and the lower oesophageal sphincter (gastro-oesophageal junction- physiological sphincter, no special/isolated muscle)
Upper one third is striated muscle, somatic sensation, voluntary control
Lower two thirds, smooth muscle, visceral sensation, involuntary control
Function to transport food using helical peristaltic movements
kidneys
Two bean shaped organs located in retroperitoneal abdomen between T12-L3 mostly protected by ribs
Filter the blood: roughly 150Litres per day (30x total body volume)
Regulate blood pH, volume, pressure and osmolality
Produce hormones: erythropoietin, renin and 1,25-dihydroxy vitamin D
Renal hilum is the entry and exit point for all blood, lymph and nerve vessels and ureters.
Biochemical measurements of kidney function: eGFR, BUN and creatinine
Structure:
Renal fascia outermost layer
Adipose capsule
Renal capsule
Outside rim in renal cortex: divided into outer cortical zone and inner juxtamedullary zone
Inner is the medulla: 10-18 renal pyramids make up the medulla. The tips of these pyramids are called renal papilla, these project into minor calyces, which collect forming major calyces and drain into the renal pelvis. Ureter connects to the renal pelvis.
Roughly 1 million nephrons per kidney
nephrons
Roughly 1 million per kidney
Divided into the renal corpuscle (begins filtration) made of the glomerulus (capillaries) and the bowman’s capsule (renal cells and basement membrane surrounding capillaries)
Podocytes line the basement membrane which form the basement membranes filtration slits allowing passage to water, glucose, ionic salts, but preventing passage of large proteins and RBCs
The wider diameter of the afferent arteriole compared to the efferent increases the pressure within the glomerulus (hydrostatic pressure) forcing water and solutes out of the capillaries into the bowman’s capsule forming the glomerular filtrate (around 170-180 L per day
Filtration + secretion + reabsorption = urine
Filtrate then passes into the renal tubule
Divided into the proximal convoluted tubule, Loop of Henle, distal convoluted tubule and the collection duct which sends the filtrate into the calyces.
All around these tubes are blood capillaries to reabsorb necessary solutes from the tubules filtrate
Filtrate is fine tuned based on the osmolarity of the blood in the surrounding capillaries
Reabsorption of Na, Cl, K ions and water occurs throughout
Once passed through this, remaining filtrate drains into the minor calyces, major calyces then the renal pelvis.
From here drains into the ureter
juxtaglomerular complex
Located between the afferent arteriole and DCT
Helps to regulate blood pressure and glomerular filtration rate
Made up of three cell types: macula densa cells, extraglomerular mesangial cells and juxtaglomerular cells
Macula densa cells are located in DCT, detect when Na, Cl levels are low, send signal to JG cells (located in wall of afferent arteriole)
Signalling is assisted by the extraglomerular mesangial cells
JG cells independently detect low BP and also receive signal from MD cells and will secrete renin to increase Na reabsorption, increase blood volume, increase constriction of blood vessels and increase blood pressure
