ANATOMY HNS; Lecture 1, 2, 3 - Cranium, meninges and brain, Vertebral column, Neck Flashcards
What are the bones in the head?
Skull: 22 total (w/out ossicles of ear); mandible, cranium, viscerocranium
What are the meninges?
3 layers -> Dura mater, arachnoid mater, pia mater
What is the dura mater?
Thick and inelastic with 2 layers (periosteal and meningeal - most places fused together but sometimes periosteal breaks away and it is filled with blood called sinuses which drain the csf impurities
What is the arachnoid mater?
Avascular, elastic - spider-like projections
What is the pia mater?
Innermost, thin, delicate layer
What is a herniation and give examples?
Space occupying lesion (e.g. blood, tumour, oedema, cyst) in any compartment may raise intracranial pressure and lead to herniation of part of brain.
What are the 3 herniation types?
Subfalcine (no clinical significance), uncal (Affects midbrain causing unconciousness) and tonsillar (affects medulla causing cardiorespiratory failure)
What holds the bones of the skull together?
By fibrous joints called sutures - fontinelles present in babies for ease of birth through birth canal and fuse later in life
Why is the sphenoid bone important?
Middle meninges artery is behind this bone, which means that a rupture can cause a huge build up of pressure leading to the need to drill to open up and reduce the pressure
What passes through the formaina in the skull base?
CN and vessels supplying the brain
What are the 3 divisions of the cranial fossa?
Anterior, middle and posterior holding different parts of the brain - ant.=frontal lobe, middle = temporal and post= cerebellum
What are the major holes in the skull and what goes through them?
X
Where is the epidural space in the CNS?
In the spine which can be used for epidural injections for labour, whereas in brain there is no extra space
What are the different dural folds?
Have issues due to being rigid so herniatin can occur if there is a space occupying lesion, causing imtracranial pressure to increase
Why is the cavernous sinus a clinically relevant structure?
Artery is present inside the sinus, and if a thrombus is present the could impinge on CN (3 or 4 different ones)
What is are the 2 main functions of the vertebral column?
Support and protection; movement
What are the support and protection functions of the vertebral column?
Body weight, transmits forces, supports the head and upper limbs, protects the spinal cord
What does the vertebral column aid in movement?
Upper limbs and ribs (extrinsic muscles), postural control and movement (intrinsic muscles)
What are the 5 regions of the vertebral column?
Cervical, thoracic, lumbar, sacrum, coccyx
What are the curvatures of the vertebral column in adult vs newborn?
x
What are the different types of curvatures?
1ry is the same as the fetal position and 2ry is in the other direction -> Lordosis is common in pregnant women, scoliosis is most common in pre-pubescent girls (thought to be associated with hormonal changes)
How many bones in the vertebral column and how many in each section?
33 vertebrae -> 7 cervical, 12 thoracic, 5 lumbar, 5 sacral (fused), 4 coccygeal (fused); size of vertebrae increase due to increase of weight on the vertebrae
How does a typical vertebra look?
How is a typical vertebrae adapted for its function?
Vertebral body is the major weight bearing part; vertebral arch forms roof of vertebral canal, has projections for attachments of muscles and ligaments, has sites of articulation for adjacent vertbrae; pedicles anchor the vertebral arch to the vertebral body
How do the typical vertebrae of the cervical, thoracic and lumbar look?
Foramen transversarium is for the cerebral arteries to move through (don’t exist on other parts of the vertebral column)
What are the atypical vertebrae?
Atlas (C1), axis (C2)
How does atlas look and differ from the other vertebrae?
NB: Allows movement in many directions; the articulate surface articulates with the skul; also no vertebral body
How does axis look and differ from the other vertebrae?
NB: Dens (vertebral body of C1 fused onto C2)
What are the ligaments between the occipital bone and the atlas; the atlas and the axial bones called?
Atlanto-occipital joint (YES), atlanto-axial joint (NO) -> Cruciform ligament stabilises the dens, alar ligament attaches from occipital bone to the dens
Which other ligaments are present in the vertebral column?
Posterior/Anterior longitudinal ligament, ligamentum flavum, inter/supraspinous ligament
What is the structure of the intervertebral discs?
Provide weight bearing and movement of heavy loads, allowing large range of movement -> Annulus fibrosus (rigid) and nucleus pulposus (jelly-like) which can rrupture and ooze out causing nerve impingement
How do the spinal nerves emerge from the vertebrae?
C1-7 above the vertebrae and C8-coccygeal from below the vertebra (30 vertebrae and 31 nerves)
What are prolapsed vertebral discs?
Occurs mostly between L5 and S1 due to the large change in angle at the sacrum -> Impinges on nerve root or on the cauda equina (medical emergency)
What are the 4 movements of the spine?
NB: Flexion to foetus
Which muscles are used in flexion and extension, lateral flexion and rotation of the spine?
Which are the extrinsic and intrinsic muscles attached to the spine?
Which set of muscles associated with the spinal column does the posterior ramus and the anterior ramus innervate?
Posterior innervates intrinsic muscles and anterior (larger) innervates extrinsic
What is the range of motion of the cervical spine?
What is the range of motion of the thoracolumbar spine?
What are the vertebral meninges?
Epidural space in the vertebral column
Where is the needle injected in epidural and spinal anaesthesia?
Epidural given during labour
Where would you insert the needle for caudal-epidural and trans-sacral anaesthesia?
Needle can be inserted in the sacral hiatus
What are some common spinal pathologies?
Low back pain, prolapsed intervertebral disc (sciatica), spondylolysis, spondolysis, spondylolisthesis, spondylitis
What is spondolysis?
Degeneration - causes decrease in height of spine and compression of emerging nerve or spinal cord
What is spondylolysis?
Stress fracture of pars interarticularis
What is spondylolisthesis?
Forward displacement of vertebra
What is spondylitis?
Inflammation of vertebrae
What are some common spinal injuries?
Occipital condyles, Jefferson fracture of C1, hyperextension injury, dislocations of cervical vertebrae
What are the most common causes of spinal injuries?
Broken neck or back due to road traffic accidents, accidents during sports/recreation, falls
How can the nerve be impinged in between 2 vertebrae?
There can be hypertrophy of the intervertebral ligament which can narrow the intervertebral hole for the nerves to pass through
What is the cauda equina?
A collection of nerves descending in the vertebral column from L2 to the sacral, wrapped in pia mater
What are the functions of the neck?
Structural -> support and moving head (inside prevertebral fascia); visceral functions -> inside/associated with pretracheal fascia; conduit for blood vessels/nerve -> inside/associated with carotid sheaths
Identify the pretracheal, prevertebral and the carotid sheaths in the diagram
x
Transverse slice through neck - ID infrahyoid muscles, pretracheal, prevertebral layers, carotid sheath sternocleidomastoid muscle
What are the levels of the neck?
C1 - open mouth; C2 - superior cervical ganglion; C3 - body of hyoid; C4 - upper body of thyroid cartilage and bifurcation of common carotid artery; C6 - cricoid cartilage, middle cervical ganglion; C7 - inferior cervical gangion
What are the triangles of the neck?
POST bordered by: Ant edge of trapezius muscle and post border of SCM and clavicle; ANT bordered by angle of mandible and ant edge of SCM
What is present in the anterior triangle of the neck?
Mainly muscles: platysma (supplied by facial nerve), mylohyoid, digastric (2 nerve supplies), infrahyoid (strap) muscles - thyrohyoid muscle, omohyoid muscle, sternothyroid muscle (all muscles useful in swallowing and talking)
What is present in the posterior triangle of the neck?
Mainly vessels and nerves: EJV (test heart function by lying patient with head lower than heart and watching it fill up and when they stand up it should all drain away), IJV (larger than EJV as it drains the brain), SCA, SCV, trunks of brachial plexus, phrenic nerve, vagus nerve (carotid sheath), spinal accessory nerve (motor nerve supplying trapezius)
What is present in the root of the neck?
Strap muscles going towards the hyoid bone; recurrent laryngeal nerve, vagus, subclavian artery sits behind the scalene muscle and the vein sits in front
Where are the different points of lymphatic drainage located in the neck?
What are the characteristics of lymph nodes in the neck?
Oval bean shaped; around 1-2mm to 1-2cm -> around 200 in the neck
What causes lymph node enlargement?
Infection/inflammation (local, generalised, in gland); neoplastic (of node or metastatic)
How do you find out whether the lymph node enlargement is due to infection/lymphoma/metastasis?
History, examination (PNS, pharynx, larynx), investigations (FNA cytology, scan)
How does the lymph flow from nodes to nodes in the neck?
What are the majority of the cancers present in the neck and how do you know if the patient has it?
Squamous cell carcinoma; history -> smoking, ulcer in mouth; examination -> using scope; nasoendoscopy, CT/MRI/PET, Bx and palpitation; IgA Ab
How would you examine the neck to check for lymph node enlargement?
Palpate around ant triangle and then post triangle; then deep under the sternacleidomastoid
What are the different lymph node levels in the neck?
What are the different risk factors which increase metastatic risk into the lymph nodes?
Depth of invasion; location of tumour (in larynx doesn’t really affect lymphatic drainage, but at start of oesophagus can cause damage/complications)
How do you treat cancers in the neck?
Remove the lymph nodes surgically which are most likely to be involved but preserve every other part in the skin; radiotherapy of the neck (which burns the skin)
