Week 1 Anatomy

Branchial arches

In the development of vertebrates, the pharyngeal arches are primordia for a multitude of structures. In the human embryo (where the vasculature of the pharyngeal arches is also known as the aortic arches), they develop during the fourth week as a series of mesodermal outpouchings on both sides of the developing pharynx. In fish, the branchial arches support the gills.

  • Between the ectoderm Branchial clefts and endoderm pharyngeal pouches
  • They eventually develop into the face, jaw, pharynx
  • 6 pairs
  • Nerve supply from cranial nerve, splanchnic mesoderm – so structurally same as skeletal muscle(voluntary) but usually covered by mucosa or near a mucocutaneous junction. Involved in superficial reflexes and glandular secretion


Tension Lines in Skin

  • Relaxed skin tension lines(Kraissl) – cuts parallel cause less scarring. Langer is cleavage lines in cadaver.


Types of cartilage

  • Hyaline – most common, weakest, has perichondrium – ribs, nose, larynx, trachea. Is a precursor of bone.
  • Fibro- strongest, no perichondrium – intervertebral discs, joint capsules, ligaments.
  • Elastic – maintains shape, has perichondrium- external ear, epiglottis and larynx.


Muscle form types (unipennate, bipennate etc.) and examples.

  • Form is determined by arrangement of muscle fibres – parallel, unipennate(tib posterior), bipennate(rectus femoris), multipennate(deltoid). Parallel ones shorten more.


Types of joints (and examples).

  • Fibrous – solid and no joint cavity- bones bridged by fibres eg cranial sutures, syndesmosis, gomphosis
  • Cartilagenous – solid and No joint cavity. primary cartilagenous are two bones bridged by hyaline cartilage(epiphyseal plates of long bones), secondary cartilagenous are always in midline – bone-hyaline cartilage- fibrocartilage -H-B eg intervertebral discs, pubic symphysis, manubriosternal angle. – allow little bit of movement.
  • Synovial – joint cavity lined by synovial membrane, articular surfaces covered in hyaline cartilage – eg knee, elbow made for movement.
    • Plane (facet joint)
    • Uni axial, bi axial and multi axial
    • Simple/compound/complex(joint cavity subdivided into multiple compartments- sternoclavicular joint)


Hilton’s Law.

  • The nerve supplying a muscle that extends across or acts at a joint also innervates that joint


Stability of joints

  • Bony – congruity of articular surfaces
  • Ligamentous – fibrous capsule(intrinsic), collaterals, cruciates, accessory(AC joint)
  • Muscular – popliteus, rotator cuff – more important in more mobile joints.
  • Other – fibrocatilage, menisci, labrum
  • Maximal stability is at the close packed position


Dermatomes / axial lines.

  • Overlap for adjacent dermatomes that are consecutive have significant overlap – pain and temp more than touch
  • So adjacent dermatomes that aren’t conseq don’t overlap and cutaneous nerve branches don’t cross axial lines.



  • Hip flexion: L2,3
  • Hip extension: L4,5, S1 (4 muscles, like triceps)
  • Hip abduction: L4, 5, S1 (absolutely same as ext)
  • Hip adduction: L2,3,4 (add one)
  • Knee flexion: L5, S1 (turn point)
  • Knee extension: Kick L2,3,4
  • Ankle dorsiflexion: Toe high L4,5
  • Ankle plantar flexion:  S1,2 tippy toe
  • Inversion: toe inside L4,5
  • Eversion: weird one L5, S1
  • Great toe ext: toe high plus one L4,5,S1


  • Shoulder abduction: C4,5,6 chicken tonight
  • Elbow flexion: C5,6 pick up sticks
  • Elbow extension: C7, 8 put em straight
  • Wrist flexion: 6,7,8 get on your bike
  • Wrist extension: short triceps 6,7
  • Finger abduction: C8, T1 muscles of hand
  • Finger adduction: T1
  • Thumb abduction: T1



  • Knee: knee ext: L2,3,4
  • Ankle: plantar flexion: S1,2
  • Plantar: 5 tippy toes: L5, S1,2
  • Triceps: 7,8
  • Biceps: 5,6
  • Supinator: 5,6
  • Finger: 8


Organisation of autonomic nervous system.

  • Central/peripheral. Somatic/visceral. Sympathetic/parasympathetic/enteric
  • Sympathtic
    • Thoracolumbar outflow T1- L2 – control smooth muscle tone of arterioles. Sympathetic trunk and gnaglion where visceral efferents synapse.
    • Dilate pupils and bronchioles, adrenaline, ejaculation
  • Parasympathetic
    • Craniosacral outflow – CN III, VII, IX, X and S2-4
    • Bradycardia, salivation, lacrimation, accomodation, miosis, erection


Organisation of a spinal nerve.

  • 31 pairs of spinal nerves.
  • Posterior nerve roots are purely sensory and anterior are purely motor. Dorsal root ganglion houses the nerve body of the afferent.
  • Spinal nerve is once the ant and post nerve roots join –> after spinal nerve you can split to ant and posterior rami.



  • Artery – endothelium, intima, media, adventitia
  • Elastic then muscular arteries. Arterioles have the largest wall thickness to lumen ratio. Greatest BP drop occurs over arterioles.
  • Capillaries – single layer endothelium with basement membrane.



  • Accompany veins, usually have a blind start. Are in the dermis. Drain to atleast one LN before draining into vein
  • Ant thorax, skin of glans penis and clitoris drain direct to deep LN
  • Watersheds- vertical and horizontal.
  • R lymphatic duct and Thoracic duct – origin of R and L brachicephalic veins.



  • Are separators eg investing fascia, retinaculum, septa. Made of collagen fibres. Deep is dense, superficial is loose.
  • Deep – nonelastic and gives attachment site for muscles. Eg palmar and plantar aponeurosis.
  • No deep fascia in face and other areas that expand a lot.
  • Mobile fascial planes are two sheets parallel to each other- give path of least resistance. Vessels and liquid may course along it. Vessels do not pierce it cos it can get kinked with movement. Vessels/nerves pierce fixed fascia.