Anatomy Flashcards
What are the functions of skin?
- an essential barrier between the external environment and the internal body contents
- it protects against mechanical, chemical, osmotic, thermal and UV damage and microbial invasion
- a role in the synthesis of vit D
- regulation of temperature
- psychosexual communication
- a major sensory organ for touch, pain, temperature and other stimuli
What is glabrous skin?
Thick skin round over the palms, soles of the feet and flexor surfaces of the fingers that is free of hair
How many layers of the skin are there and what are they?
- epidermis
- dermis
- hypodermis
What is the epidermis made up of?
Largely layers of keratinocytes
Non-keratinocytes
* melanocytes
* landerhans cells
* merkel cells
What is cornification?
Keratinocytes undergoing terminal maturation - this involves keratin production and migration towards the external surface, a process called cornification
What is the role of melanocytes?
They are responsible or melanin production and pigment formation
What is a Langerhans cell?
It is an antigen-presenting dendritic cell
What are Merkel cells?
sensory mechanoreceptors
What are the layers of the epidermis and what happens in them?
From deepest to superficial:
Stratum basale - mitosis of keratinocytes occurs here
Stratum spinosum - keratinocytes are joined by tight intercellular junctions ‘desmosomes’
Stratum granulosum - cells secrete lipids and waterproofing molecules in this layer
Stratum lucidem - cells lose nuclei and drastically increase keratin production
Stratum corneum - cells lose all organelles but continue to produce keratin
Brownie Spoons Get Licked Constantly
How is the dermis bound to the epidermis?
Through a highly corrugated dermo-epithelial junction
How many layers does the dermis have and what are they?
- Superficial papillary layer
- Deeper thicker reticular layer
What are the cell types and structures found in the dermis and what are their functions?
- Fibroblasts these cells synthesise the extracellular matrix (collagen and elastin)
- Mast cells histamine granule-containing cells of the innate immune system
- Bloods vessels and cutaneous sensory nerves
- Skin appendages hair follices, nails, sebaceouns and sweat glands
What is a pilosebaceous unit?
A combination of the hair follicles and a sweat gland
How do sebaceous cysts release their glandular secretions?
Via a holocrine mechanism into the hair follicle shaft.
What are the two types of sweat gland and how are they different?
- Eccrine glands the main sweat gland of the body, releases a clear odourless substance, comprised of sodium and water for thermoregulation
- Apocrine glands larger sweat glands, located in the axillary and genital regions, the products can be broken down by cutaneous microbes, producing body odour
What is the hypodermis made of and what is it’s function?
It is a major store of adipose tissue, so can vary in size depending on the person
What is hair made of?
Hair is a keratinous filament growing out of the epidermis. It is primarily made of dead, keratinised cells
What is the hair shaft?
The part of the hair not anchored to the follicle, mostly exposed at the skin surface
What makes up the hair bulb?
The hair root ends deep in the dermis at the hair bulb and includes a layer of mitotically active basal cells called the hair matrix. The hair bulb surrounds the hair papilla, which is made of connective tissue and contains blood capillaries and nerve endings from the dermis
What are the layers of the hair?
- Medulla forms the central core
- Cortex a layer of compressed keratinised cells
- Cuticle an outer later of very hard, keratinised cells
What are the three different types of muscle and how are they different?
- Skeletal striated muscle that is under voluntary control from the somatic nervous system - identifying features are cylindrical cells and multiple peripheral nuclei
- Cardiac striated muscle that is only found in the heart - identifying feature are single nuclei and the presence of intercalated discs between the cells
- Smooth non-striated muscle that is controlled involuntarily by the autonomic nucleus per cell
What type of muscle has cylindrical cells and multiple peripheral nuclei?
Skeletal muscle
What is a sarcolemma?
A single cell forms a muscle fibre and its cell membrane is known as the sarcolemma
What type of muscle has singular nuclei and intercalated discs?
Cardiac
What are T tubules?
They are invaginations of the sarcolemma that conduct charge when the cell is depolarised
They are unique to muscle cells
What is the specialised endoplasmic reticulum that muscles have and what ion does it store?
Sarcoplasmic reticulum - large stores of calcium
Muscles have an intricate support structure of connective tissues…. describe it
- Each muscles fibre is surrounded by a thin layer of connective tissue known as endomysium
- These fibres are then grouped into bundles known as fascicles
- These are surrounded by a layer of connective tissue known as perimysium
- Many fascicles make up a muscle, which in turn is surrounded by a thick layer of connective tissue known as epimysium
What are the two contractile filaments in skeletal muscle?
Actin (thin filament) and Myosin (thick filament)
What is a sarcomere?
The function unit of contraction in a skeletal muscle fibre, it runs from Z line to Z line
Label this sarcomere and what the areas represent
Z line - where the actin filaments are anchored
M line - where the myosin filaments are anchored
I band - contains only actin
H zone - contains only myosin
A band - the lenght of a myosin filament, may include overlapping actin filaments
A useful acronym is MHAZI – the M line is inside the H zone which is inside the A band, whilst the Z line is inside the I band.
What two other regulatory proteins are associated with actin and what do they do?
- Troponin a small protein that binds the tropomyosin to the actin
- Tropomyosin a long protein that runs along the actin filament and blocks the myosin head binding sites
What are the three types of troponin and what do they do?
- Troponin I binds to the actin filament
- Troponin T binds to the tropomyosin
- Troponin C can bind to calcium ions
What are the stages of the excitation-contraction coupling on troponin/actin/myosin?
- Depolarising occurs at a neuromuscular junction, this is conducted down the t-tubules, causing a huge influx of calcium ions into the sarcoplasm from the sarcoplasmic reticulum
- Calcium binds to Trop C, which moves tropomyosin away from the myosin binding sites of actin
- Myosin head binds to actin, the power stroke pivots the myosin heads in a rowing motion, moving the actin towards the M line
- ATP then binds to the myosin head, causing uncoupling so it can happen again
What happens to the length of the sarcomere and its zones during the excitation-coupling?
- The length of the filaments do not change
- The sarcomere decreases in size
- The H zone and I band decrease in size
- The A band stays the same
- The Z lines come closer together
Where are tendons situated and what are the joining points called?
Tendons are between bone and muscle
The point at which the tendon joins the muscle is called the myotendinous junction
The point at which the tendon joins the bone is called the osteotendinous junction - it is attached by collagenous fibres called ‘Sharpey fibres’ that continue into the bone matrix
What is the origin, insertion and purpose of a tendon?
The origin is the proximal attachment of the tendon
The insertion is the distal attachment of the tendon
The purpose of a tendon is to transmit forces generated by the muscle to the bone to ellicit movement
What is a tendon mainly made of?
- Mainly type 1 collagen fibres - responsible for strength
- Proteoglycan - responsible for viscoelastic nature
What are the units of tendon composition?
- Primary collagen fibres, which consist of bunches of collagen fibrils, are the basic units of a tendon
- Primary fibres are bunches together to form subfasicles, groups of which bunch together to form secondary fasicles
- Fasicles bind together to form a tendon unit
- All the bundles are surrounded by a sheath of connective tissue called endotenon
- Endotenon in contiguous with epitenon, the fine layer of connective tissue that sheaths the tendon
What are tendon cells called and where do you find them?
- Tenoblasts - immature cells that give rise to tenocytes - occur in clusters, free from collagen fibres
- Tenocytes - mature cells found throughout the tendon structure, typically anchored to collagen fibres
What are the functions of bone?
- Haematopoiesis
- Lipid and mineral storage - bone is a reservior holding adipose tissue within the bone marrow and calcium within the hydroxyapatite crystals
- Support - bones form the framework and shape of the body
- Protection - especially the axial skeleton that surrounds the major organs of the body
What are the three types of cells in bone and their functions?
- Osteoblasts synthesise uncalcified/unmineralised extracellular matrix called osteoid
- Osteocytes as the osteoid mineralises, the osteoblasts become entombed between the lamellae in lacunae, where they become osteocytes, which monitor the minerals and proteins to regulate bone mass
- Osteoclasts are derived from monocytes and resorb bone by releasing H+ ions and lysosomal enzymes. They are large and multinucleated
What is the bone extracellular matrix and how is it organised?
It refers to the molecules that provide biochemical and structural support to cells
The matrix is organised into thin layers, known as lamellae
What is the main mineral salt in bones and what does it do?
Calcium hydroxyapatite associates with the collagen fibres, making bone hard and strong
Under the microscope, bone can be divided into two types.
What are these types and what are the differences between them?
- Woven bone (primary bone) - appears in embryonic development and fracture repair, as it can be laid down rapidly. It consists of osteoid (unmineralised ECM), with the collagen fibres arranged randomly. It is a temporary structure, soon replaces by lamellar bone
- Lamellar bone (secondary bone) - the bone of the adult skeleton. It consists of highly organised sheets of mineralised osteoid. This organised structure makes it much stronger than woven bone. Lamella bone itself can be divided into two types - compact and spongy
What are the periosteum and the endosteum?
- Periosteum is a layer of connective tissue, which covers the external surface of bone
- Endosteum lines the cavities within bone, such as the medullary canal, Volkmann’s canal and spongy bone spaces
What are the two types of lamellar bone and what are their properties?
- Cortical bone - which is compact, dense and rigid, containing Volkmann’s and Haversian canals
- Trabecular bone - spongy bone, marked by many interconnecting cavities, doesn’t contain Haversian and Volkmann’s canals
What is the structure of cortical bone?
- The lamellae are organised in concentric circles, which surround a vertical Haversian canal (transmits small neurovascular and lymphatic vessels). This entire structure is called an osteon.
- The Haversian canals are connected by horizontal Volkmann’s canals which anastomaose with the arteries of the Haversian canals.
- Osteocytes are located between the lamellae, within lacunae, which are interconnected by a series of tunnels called canaliculi
Where is bone marrow within the bone and what are the different types of bone marrow?
The spaces between trabeculae in trabecular bone is often filled with bone marrow
* Yellow bone marrow containes adipocytes
* Red bone marrow consists of haematopoietic stem cells
What are the two mechanisms of ossification (building new bone) and an example for each?
- Endochondral ossification - where hyaline cartilage is replaced by osteoblasts secreting osteoid - an example is femur
- Intramembranous ossification - where mesenchymal (embryonic) tissue is condensed to bone - an example is temporal bone and the scapula
How are the airways in children different from adults and what does this mean?
Narrower airways increase the risk of obstruction from:
* swelling (croup)
* foreign bodies (small toys or food)
* nasal mucous (from bronchiolitis
* large tongues
How is the oxygen consumption different in children and why?
Increased oxygen consumption due to higher respiratory rate driven by a higher metabolic rate
How does the increased respiratory rate in children affect water loss from the lungs?
It increases the water loss
How are children’s alveoli different and what is the effect of this?
Children have smaller and fewer alveoli, resulting in limited alveolar surface area for gas exchange and more dead space in the airway.
Infants must breathe faster to achieve adequate minute ventilation
How is fluid loss due to evaporation different in children?
Vulnerable to greater fluid loss through evaporation from their large body surface area. They require greater fluid requirements to maintain adequate circulating volume
How do children physiologically alter their cardiac output?
They increase their heart rate to increase their cardiac output due to their difficulty changing stroke volume. Their heart is large in relation to body size and has less contractile efficiency
How is temperature regulation susceptibility different in children?
Temperature regulation is not well developed. Exposure can result in hypothermia for neonates and infants. There are also susceptible to heat loss from the surface of their head when exposed.
When does the anterior and posterior fonatanelle remain open til?
Anterior - 12-18 months of age
Posterior - 2-3 months of age
How does having a higher metabolic rate effect children?
- Increased waste production
- Increased fluid and nutrition requirements
- More susceptible to rapid fluid loss
- Higher respiratory rate
- Increased oxygen consumption
- Higher cardiac output
- Higher oxygen delivery
- Increased workload for cardiovascular system
What is the expected urine output of a child?
1-2ml/kg/hr
What is the macro-organisation of skeletal vs smooth vs cardiac muscle?
Skeletal muscle
fascicles and motor unit
Smooth muscle
sheets and bands
Cardiac muscle
function syncytium
What is the innervation of skeletal vs smooth vs cardiac muscle?
Skeletal muscle
voluntary motor, every cell, no automaticity
Smooth muscle
autonomic, not every cell, automaticity
Cardiac muscle
autonomic, not every cell, limited automaticity
What is the metabolism of skeletal vs smooth vs cardiac muscle?
Skeletal muscle
High energy requirements, fatiguable, very fast conduction
Smooth muscle
Low energy requirements, non-fatiguable and slow conduction
Cardiac muscle
Extremely high energy requirements, non-fatiguable, fast conduction
What is the histology of skeletal vs smooth vs cardiac muscle?
Skeletal muscle
Huge and long, multinucleated cells arranged in sarcomeres with T-tubules
Smooth muscle
Very small single nucleus disorganised cells with cavolae
Cardiac muscle
Small binucleated cells arranged in sarcomeres with T-tubules
What are dense bodies in the smooth muscle and what do they do?
The contractile elements of the smooth muscle insert along the entire length of the myocyte, anchored to ‘dense bodies’.
They are rigid and rather large. They function as attachment points for intermediate filament cables made of desmin and contractile actin filaments
What is the central nervous system vs the peripheral nervous sytem?
Central nervous system is made up of the brain and the spinal cord
Peripheral nervous system is made up of cranial and spinal nerves, ganglia, plexuses, and sensory receptors
What is the autonomic nervous system?
It is the part of the nervous sytem that is responsible for homeostasis. Except for skeletal muscle, innervation to all other organs is from the ANS.
Classic definiton: preganglionic and postganglionic neurons within the sympathetic and parasympathetic divisions
What are the two divisons of the autonomic nervous system?
Sympathetic & Parasympathetic
Some target organs are innervated by both divisons and others are controlled by only one
What are the differences between preganglionic and post-ganglionic neurons?
The cell bodies of the preganglionic neurons are located in the intermediolateral (IML) column of the spinal cord and in motor nuclei in the cranial nerves.
The axons of the preganglionic neurons are small-diameter, myelinated, relatively slow conducting B fibers
The axons of the postganglionic neurons are mostly unmyelinated C fibers and terminate on the visceral effectors
How many postganglionic neurons does a preganglionic axon diverge to?
Usually around 8 or 9.
In this way, autonomic output is diffuse
How do alpha-motor neurons differ from preganglionic axons?
In contrast to the large diameter, rapidly conducting alpha-motor neurons, preganglionic axons are myelinated, relatively slow conducting B fibers
What neurotransmitter is released by all neurons whose axons exit the CNS and what neurons does this include?
Acetylcholine
It is released by cranial motor neurons, alpha-motor neurons, gamma-motor neurons, preganglionic sympathetic neurons, and preganglionic parasympathetic neurons
What neurotransmitters do postganglionic sympathetic and postganglionic parasympathetic neurons release?
Postganglionic parasympathetic neurons also release acetylcholine
Postganglionic sympathetic neurons release either norepinephrine or acetylcholine
Where are the sympathetic preganglionic neurons situated?
In contrast to alpha-motor neurons, which are located at all spinal levels - sympathetic preganglionic neurons are located in the IML of only the first thoracic to the third or fourth lumbar segments
What is the path of the sympathetic neurons?
- The preganglionic sympathetic neurons leave the spinal cord at the level of the vertebral body
- They exit via the ventral root the seperate from the ventral route via the white rami communicans, they project to the adjacent sympathetic paravertebral ganglion
- Some of them end here on the cell bodies of the postganglionic neurons
- Some of them pass through the sympathetic chain and end on postganglionic neurons located in prevertebral (or collateral) ganglions
- Some of them leave the chain ganglia and re-enter the spinal nerves via the grey rami communicans
What is the sympathetic chain?
Paravertebral ganglia are located adjacent to each thoracic and upper lumbar spinal segment, there are a few ganglia adjacent to the cervical and sacral spinal segments
They are all connected together via the axons of preganglionic sympathetic neurons that travel rostrally or caudally. Together these axons and ganglia for the sympathetic chain
Where are the preganglionic parasympathetic ganglions?
They are located in several cranial nerve nuclei (III, VII, IX, and X)
What makes up the cerebrum?
It includes the cerebral hemispheres and the basal ganglia.
The cerebral hemispheres are separated by the falx cerebri within the longitudinal cerebral fissure
Label this diagram with the sulci, prominent gyri and lobes
What is the diencephalon?
It consists of:
epithalamus
dorsal thalamus
hypothalamus
It forms the central core of the brain
Where is the midbrain? Which cranial nerves is it associated with?
The rostral part of the brain, it lies at the junction of the middle and posterior cranial fossa.
CN III and IV
Where is the pons? What cranial nerve is associated with it?
The part of the brainstem between the midbrain rostrally and the medulla oblongata caudally. It lies in the anterior fossa.
CN V is associated with it
Where is the medulla oblongata? What cranial nerves are associated with it?
It is the most caudal subdivision of the brainstem that is continuous with the spinal cord - it lies in the posterior cranial fossa.
CN IX, X, XI, XII
What does the ventricular system of the brain consist of?
It consists of two lateral ventricles, and the midline 3rd and 4th ventricles connected by the cerebral aqueduct. CSF fills the ventricles
Where does CSF travel out of the ventricles?
It is created in the ventricles.
It either drains into the subarachnoid space via the fourth ventricle through a single median aperture and paired lateral apertures.
or
CSF flows into the subarachnoid cisterns and from there travels through the sulci and fissures of the cerebral hemispheres
What happens if the median and lateral apertures get blocked?
The CSF gets trapped and you get hydrocephalus
What are subarachnoid cisterns?
At certain areas on the base of the brain, the arachnoid and the pia are widely separated by the subarachnoid cisterns, which contain CSF and soft tissue structures that anchor the brain
How much CSF is secreted daily and how does it happen?
400-500mls/day
Mainly secreted by the choroidal epithelial cells of the choroid plexus in the lateral, third and fourth ventricles
They are on invaginations in the roof of the third and fourth ventricles and the floor of the lateral ventricles
How is CSF absorbed?
The main site of CSF absorption is through the arachnoid granulations. It extends into the cores of the arachnoid granulations. It enters the venous system through two routes
1. mostly by transport through the cells of the arachnoid granulations into the dural venous sinuses
2. moves between the cells making up the arachnoid granulations
What is the function of the spinal cord?
It is the major reflex center and conduction pathway between the body and the brain
What structures protect the spinal cord?
The cyclindrical structure, slightly flattened anteriorly and posteriorly, is protected by the vertebrea, their associated ligaments and muscles, the spinal meninges and CSF.
Where does the spinal cord start and end?
It begins as a continuation of the medulla oblongata.
In adults it is 42-45cm long.
It extends from the foramen magnum to the levels of L1-L2
The spinal cord is enlarged in two regions in relationship to innervation of the limbs. Where are these?
- The cervical enlargement extends from C4 to T1 and most of the anterior rami of the nerves arising from it form the brachial plexus
- The lumbosacral enlargement extends from T11 to S1 - the anterior rami of the nerves arising from it form the lumbar and sacral plexuses
How many cervical nerve roots are there and what level do they exit the canal?
8
C1 passes superior to the arch of C1 vertebrae
C2-7 pass through foramina superior to their vertebrae
C8 passes through the foramina in between C7-T1 (note there is no C8 vertebrae, only the nerve!)
How many thoracic nerve roots are there and what level do they exit the canal?
12
They all pass through foramina inferior to their corresponding vertebrae
How many lumbar nerve roots are there and what level do they exit the canal?
5
They all pass through foramina inferior to their corresponding vertebrae
How many sacral nerve roots are there and what level do they exit the canal?
5
They branch into posterior and anterior rami in the sacrum, with the respective rami passing through the anterior and posterior sacral foramina
What is the filum terminale?
It arises from the tip of the conus medullaris and descends among the spinal roots, perforating the dura, continuing through the sacral hiatus as the filum terminale externum to attach to the dorscum of the coccyx to anchor the spinal cord
What does the spinal meninges consist of?
Internal to external:
Pia matter
Arachnoid matter
Dura matter
What is spinal dura matter made of?
Mainly tough fibrous tissue with some elastic fibres
What is the epidural space made of and how long is it?
The spinal dura is separated from the vertebral canal by the epidural space.
It is occupied by epidural fat.
It runs the length of the vertebral canal
How does the spinal dura merge with the brain dura?
The spinal dura forms the spinal dural sac, which adheres to the margin of the foramen magnum, where it is continuous with the cranial dura matter
How does the spinal dura merge with the epineurium (outer connective tissue protecting the spinal nerves)?
The spinal dural sac has tapering lateral extensions that surround each pair of posterior and anterior nerve roots as dural root sheaths, which blend with the epineurium
What is spinal arachnoid matter?
It is a delicate, avascular membrane composed of fibrous and elastic tissue that lines the spinal dural sac
What is the subarachnoid space and what does it consist of?
It is the space between the arachnoid and the pia matter.
It is filled with CSF and contains the spinal cord, spinal nerve roots and spinal ganglia
What is the dura-arachnoid interface?
The spinal arachnoid is not attached to the spinal dura but is held against it by the pressure of the CSF.
Their aposition is called the dura-arachnoid interface
How are the arachnoid matter and pia matter connected?
Delicate strands of connective tissue, the arachnoid trabeculae, they span the subarachnoid space connecting the spinal arachnoid and pia
What is the pia matter and what is it made of?
The spinal pia matter, the innermost covering membrane of the spin cord, is thin and transparent and closely follows all the surfaces of the spinal cord.
It covers the nerve roots and blood vessels and continues as the filum terminale.
What is the bilateral ligament that runs longitudinally on both sides of the spinal cord? What is it made of?
Where does it attach?
Denticulate ligament
It consists of a fibrous sheet of pia extending midway between the posterior and anterior nerve roots from the lateral surfaces
It attachs to the cranial dura immediately superior to the foramen magnum and extends from the conus medullaris
What is a neuron composed of?
A cell body with processes called dentrites and an axon, which carry impulses to and away from the cells, respectively
What are multipolar motor neurons? Where are they in the nervous system?
They have two or more dendrites and a single axon that may or may not have one or more collateral branches
All of the motor neurons that control skeletal muscle and comprise the autonomic nervous system are multipolar motor neurons
What are pseudounipolar sensory neurons? Where are they in the nervous system?
They have a short, apparently single (but actually double) process extending from the cell body, which separates into a peripheral process, conducting impulses from the receptor organ toward a cell body. The cell body is located outside the CNS in sensory glanglia, and are thus part of the PNS. They communicate with each other at neurotransmitter synapses.
What are neuroglia?
They are non-neuronal, non-excitable cells that form a major component of nervous tissue, supporting, insulating and nourishing the neurons.
In the CNS, what is a nucleus and where is it found?
A nucleus is a collection of cell bodies in the CNS.
They lie within and constitue the grey matter
In the CNS, what is a tract and where is it found?
A bundle of axons within the CNS connecting neighbouring or distal nuclei of the cerebral cortex is called a tract.
The interconnecting fibre tract matrix forms the white matter
What are the posterior and anterior horns?
In transverse sections of the spinal cord, the gray matter forms an H. The struts of the H are horns; hence there are right and left dorsal (posterior and ventral (anterior) horns
Nerves are fairly strong and resilient because the nerve fibres are supported and protected by three consecutive tissues coverings.
What are they?
- Endoneurium, delicate connective tissue immediately surrounding the neurilemma cells and axons
- Perineurium, a layer of dense connective tissue that encloses a fasicle of nerve fibres, providing an effective barrier against penetration by foreign bodies
- Epineurium, a thick connective tissue sheath that surrounds and encloses a bundle of fascicles, forming the outermost covering of the nerve, it includes blood vessels, lymphatics and fatty tissue
What are the two types of nerve in the peripheral nervous system?
- Afferent (sensory) fibres convey neural impulses to the CNS from the sense organs
- Efferent (motor) fibres convey neural messages from the CNS to effector organs
Spinal nerves initially arise from the spinal cord as rootlets, which converge to form two roots.
What are they and what nerves are in each root?
- Anterior (ventral) nerve root, consisting of motor (efferent) fibers passing from the nerve cell bodies in the anterior horn to effector organs
- Posterior (dorsal) nerve root, consisting of sensory (afferent) from cell bodies in the spinal or posterior root ganglion that extend peripherally to sensory endings and centrally to the posterior horn
The spinal posterior and anterior nerve roots combine and then what happens?
They form a mixed (both sensory and motor) spinal nerve, which divides into two rami : a posterior and an anterior rami, which both contain a mix or sensory and motor nerves
What is a dermatome and a myotome?
Dermatome - the unilateral area of skin innervated by the sensory fibres of a single nerve
Myotome - the unilateral muscle mass receiving innervation from the fibres conveyed by a single spinal nerve
What is the somatic nervous system? It’s broken into two systems, what are they?
It is composed of somatic parts of the CNS and PNS. It provides sensory and motor innervation to all parts of the body, expect the viscera, smooth muscle and glands
The somatic sensory system transmits senations of touch, pain, temperature and position from sensory receptors
The somatic motor system innervates only skeletal muscle, stimulating voluntary and reflexive movement by causing the muscle to contract
What does a nerve fiber consist of?
An axon, a neurolemma and surrounding endoneurial connective tissue.
Do large or small myelinated or unmyelinated fibres conduct faster?
Larger myelinated fibers conduct faster than smaller unmyelinated fibres
What types of nerves are myelinated?
A & B
What types of nerves are unmyelinated?
C
What do A alpha nerves transmit?
Somatic, motor and proprioception
What is the diameter of different types of A nerves?
Alpha - 16um
Beta - 8um
Gamma - 4um
Delta - 4um
What is the speed of the different A type nerves?
Alpha - 100m/s
Beta - 50m/s
Gamma - 25m/s
Delta - 25m/s
What do A beta nerves transmit?
Touch
What do A gamma nerves transmit?
Motor to muscle spindles
What do A delta nerves transmit?
Pain and temperature (fast pain or epicritic pain)
What do B nerves transmit?
Preganglionic autonomic
What is the diameter and speed of B nerves?
Diameter - 2um
Speed - 12.5m/s
What does a C type nerve transmit?
Pain and temperature (slow pain and protopathic pain)
Postganglionic sympathetic nerve
What is the diameter and speed of C nerves?
Diameter - 1um
Speed - 2m/s
What is the umbilicus dermatome?
T10
What dermatome supplies the nipple?
T4
What is the largest cranial nerve?
Trigeminal nerve
Where does the sensory root for the trigeminal root lie?
In the trigeminal (semilunar) ganglion that is at the apex of the petrous temporal bone
Where do the motor neurons of the trigeminal nerve begin?
The upper pons
Where do the cranial nerve nucleis lie?
First 4 cranial nerve nuclei lie above the pons
Second 4 lie in the pons
Last 4 lie below the pons
What is a myotome?
A unilateral muscle mass receiving intervention from fibres conveyed by a single spinal nerve (from the anterior ramus division)
What is a myotome?
A unilateral muscle mass receiving intervention from fibres conveyed by a single spinal nerve (from the anterior ramus division)
What myotomes do knee flexion?
L5, S1
What nerves do shoulder adduction and medial rotation?
C6, C7, C8
What myotome does great toe extension?
L5
What myotome does tibialis anterior and posterior and inversion of the foot?
L4
What myotome does extensor hallucis longus and extension of the great toe?
L5
What myotome does gastrocnemius, plantarflexion of the foot, ankle jerk?
S1
What myotome does small muscles of the foot?
S2
What nerves do pronation?
C7, C8
What nerve supplies general sensation of the mucosa of the anterior two thirds of the tongue?
The lingual nerve - a branch of CN V3 - cell bodies in the trigeminal ganglion
What nerve supplies taste on the tongue?
The chorda tympani nerve, a branch of CN VII - cell bodies in the geniculate ganglion of the facial nerve
What action does C5/6 do?
Elbow flexion
What action does C6 do?
Elbow extension, wrist extension, supination, arm adduction, medial rotation of the arm
What action does C7 do?
Incorporated into many myotomes/actions (medial rotation of elbow, adduction of arm, arm extension, elbow extension, hand flexion, pronation, digital extension and flexion
What action does C7/C8 do?
Digital flexion and extension and pronation of the hand
What does the L3 dermatome supply?
Anterior and medial thigh and knee
What does dermatome L4 supply?
Medial leg, medial ankle and side of foot
What dermatome does L5 do?
Lateral leg, dorsum of foot, medial sole, 1-3 toes
What does dermatome S1 supply?
Lateral ankle, lateral side of dorsum and sole of foot, 4-5 toes
What does dermatome S2 supply?
Posterior leg, posterior thigh, buttocks and penis
What action does L2,L3 do?
Hip flexion
What action does L4, L5 do?
Hip extension
Ankle dorsiflexion
What action does L5, S1 do?
Knee flexion
What action does L3, L4 do?
Knee extension
What action does S1 and S2 do?
Ankle plantarflexion
What are the roots that make up the brachial plexus?
C5, C6, C7, C8 and T1
What are the sections of the brachial plexus called?
Roots -> trunks -> divisions -> cords -> branches
What are the trunks of the brachial plexus?
Superior middle and inferior
Which roots make up which trunks in the brachial plexus?
C5&6 - superior
C7 - middle
C8/T - inferior
Which trunks make up the cords of the brachial plexus
Superior and middle - lateral cord
Superior, middle and inferior - posterior cord
Inferior - medial cord
Which cords make up the branches of the brachial plexus?
Musculocutaneous - lateral cord
Axillary and radial - posterior cord
Median - lateral and medial cord
Ulnar - medial cord
What eye muscles are used for eye abduction?
The superior and inferior recti
What actions does the inferior rectus muscle do?
Depressed, adducts and laterally rotates the eye
What do the oblique eye muscles do?
Adduction
What are the positions in the carotid sheath?
The carotid artery lies medial to the internal jugular vein and the vagus nerve is situated posteriorly between the two vessels
What are the boundaries of the lateral cervical region/posterior triangle ?
Sternocleidomastoid
Trapezius
Clavicle
What muscles are in the posterior triangle?
Splenius capitus
Levator scapulae
Middle scalene
Posterior scalene
What arteries are in the posterior triangle?
Lateral branches of the thyrocervical trunk
Subclavian
Suprascapular artery
Cervicodorsal trunk
Superficial cervical artery
Dorsal scapular artery
What veins are in the posterior triangle?
External jugular vein
Subclavian vein
What are the branches of the ophthalmic nerve?
Lacrimal nerve
Supraorbital nerve
Supratrochlear nerve
Infratrochlear nerve
External nasal nerve
What opens into the inferior meatus of the nose?
The nasolacrimal duct, 2cm long, slopes downwards, backwards, and laterally in conformity with the pear shaped nasal cavity, to open high up in the anterior part of the inferior meatus, 2cm behind the nostril
Which cranial nerves are pure motor?
III, IV, VI, XI, XII
What’s the acronym for cranial nerve motor vs sensory?
Some Say Money Matters, But My Brother Says Big Boobs Matter Most
What makes up the pectoral girdle?
The scapulae and the clavicles, connected to the manubrium of the sternum
What is the purpose of the pectoral girdle and how does the anatomy lend itself to this?
It possesses a large flat bone located posteriorly, which provides attachment for the proximal muscles, and connects with its contralateral partner anteriorly via small bony braces
How is the anatomy of the pectoral girdle different to the pelvic girdle to allow your arms to move independently?
It is connected to the trunk only anteriorly, via the sternum, by flexible joints with 3 degrees of freedom. It is an incomplete ring because the scapulae are not in touch with each other posteriorly.
Thus, the motion of one upper limb is independent of the other, and the limbs are able to operate effectively anterior to the body.
What is the shape of the clavicle and what are it’s joints?
The shaft of the clavicle has a double curve in a horizontal plane.
It’s medial half in convex anteriorly, and its sternal end is enlarged and triangular where it articulates with the manubrium of the sternum at the sternoclavicular joint.
It’s lateral half is concave anteriorly, and it’s acromial end is flat where it articulates with the acromion of the scapula at the acromioclavicular joint.
These curvatures increase the reslience of the clavicle
What are the main functions of the clavicle?
- Serves as a moveable, rigid support from which the scapula and free limbs are suspended, keeping them away from the trunk so increased ROM. It is movable so allows the scapula to move on the thoracic wall at the scapulothoracic joint, increasing ROM further
- Fixing the clavicle in an elevated position enables elevation of the ribs for deep inspiration
- Forms one of the bony boundaries of the cervico-axillary canal, protecting the neurovascular bundle supplying the upper limb
- Transmits shocks (traumatic) from the upper limb to the axial skeleton
What is the osteology of the clavicle?
Although designated as a long bone, the clavicle has no medullary cavity. It consists of spongy trabecular bone with a shell of compact bone
Trick question hehe
Is the clavicle rough or smooth?
- The superior surface of the clavicle, lying just deep to the skin and platysma muscle in the subcutaneous tissue is smooth
- The inferior surface of the clavicle is rough because strong ligaments bind to the 1st rib near its sternal end and suspend the scapula from its acromial end.
What ligaments join the clavicle and where?
The conoid tubercle gives attachment to the conoid ligament, the medial part of the coracoclavicular ligament, by which the remainder of the upper limb is passively suspended from the clavicle.
Also, near the acromial end of the clavicle is the trapeziod line, to which the trapezoid ligament attaches. It is the lateral part of the coracoclavicular ligament
What is the purpose of the subclavian groove?
In the medial third of the shaft of the clavicle is the subclavian groove. This is the site of attachment for the subclavius muscle.
What is the ligament joining the 1st rib to the clavicle and where does it join the clavicle?
On the medial aspect of the clavicle, there is the impression for the costoclavicular ligament, a rough, often depressed, oval area that gives attachment to the ligament binding the 1st rib to the clavicle, limiting elevation of the shoulder.
Which ribs does the scapula cover?
2nd - 7th ribs
What is the ridge that projects along the scapula? What sections does it create?
The convex posterior surface of the scapula in unevenly divided by a thick projecting ridge of bone, the spine of the scapula, into a small supraspinatous fossa and a larger infraspinatous fossa
The concave costal surface of the scapula forms what?
The large subscapular fossa
What is the shape of the body of the scapula?
The triangular body of the scapula in thin and translucent superior and inferior to the spine of the scapula; although it’s borders, especially the lateral one, are somewhat thicker
What is the acromion?
The scapula spine continues laterally as the flat, expanded acromion, which forms the subcutaneous point of the shoulder and articulates with the acrominal end of the clavicle.
What is the deltoid tubercle?
The deltoid tubercle of the scapular spine is the prominence indicating the medial point of attachment of the deltoid muscle
Where is the acromioclavicular joint?
Because the acromion is a lateral expansion of the scapula, the AC joint is placed lateral to the mass of the scapula and it’s attached muscles.
Where is the glenohumeral joint relative to the acromioclavicular joint?
The glenohumeral joint is almost directly inferior to the AC joint; thus the scapular joint is balanced with that of the free limb, and the suspending structure (coraco-clavicular ligament) lies between the two masses.
What and where is the glenoid cavity?
Superolaterally, the lateral surface of the scapula has a glenoid cavity, which receives and articulates with the head of the humerus at the glenohumeral joint.
The glenoid cavity is a shallow, concave, oval fossa, directed anterolaterally and slightly superiorly - that is considerably smaller than the ball (head of humerus) for which it serves as a socket
Where and what is the coracoid process?
The beak-like coracoid process is superior to the glenoid cavity, and projects anterolaterally.
This process also resembles in size and shape a bent finger pointing to the shoulder, the knuckle of which provides the inferior attachment for the passively supporting coracoclavicular ligament
What are the anatomical borders and angles of the scapula?
It has medial (vertebral), lateral (axillary), and superior borders and superior, lateral and inferior angle.
What makes up the scapulothoracic joint and what is it’s function?
The scapulothoracic joint is a ‘physiological’ joint, in which movement occurs between musculoskeletal structures rather than an anatomical joint. It is where the scapular movements of elevation-depression, protraction-retraction, and rotation occur.
These movements enable the arm to move freely
What is the humerus and what are it’s joints?
The humerus, the largest bone in the upper limb, articulates with the scapula at the glenohumeral joint, and the radius and ulnar at the elbow joint.
What are the points to remember at the proximal end of the humerus?
- The spherical head of the humerus articulates with the glenoid cavity of the scapula
- The anatomical neck is formed by the groove circumscribing the head and separating it from the greater and lesser tubercles. It indicates the line of attachment of the glenohumeral joint capsule.
- The surgical neck is the narrow part distal to the head and the tubercles
- The junction of the head and neck with the shaft is indicated by the greater and lesser tubercles, which provide attachment and leverage to some scapulohumeral muscles.
- The intertuberclar sulcus separates the tubercles and provides a passage for the tendon of the long head of the bicep muscle
What are the two prominent features of the shaft of the humerus?
- The deltoid tuberosity laterally, for attachment of the deltoid muscle
- The oblique radial groove posteriorly, in which the radial nerve and profunda brachii artery lie as they pass anterior to the long head and between the medial and lateral heads of the triceps brachii muscle
What is the shape of the inferior end of the humerus?
The inferior end of the humeral shaft widens as the sharp medial and lateral supra-epicondylar ridges form, and then end distally in the especially prominent medial epicondyle and lateral epicondyle, providing for muscle attachment.
What points make up the condyle of the humerus?
The distal end of the humerus - made up of the trochlea, capitulum, olecranon, coronoid and radial fossa - makes up the condyle of the humerus.
The parts that have a * next to them
What is the shape of the condyle of the humerus?
- The condyle has two articular surfaces: a lateral capitulum for articulation with the head of the radius, and a medial, spool-shaped trochlea for articulation with the proximal end (trocheal notch) of the ulna.
- Superior to the trochlea is thin due to: the anterior coronoid fossa, which receives the coronoid process of the ulna in elbow flexion; the posterior olecranon fossa accomodating the olecranon of the ulna during full elbow extension
- Superior to the capitulum anteriorly, a shallower radial fossa accomodates the edge of the head of the radius in full forearm flexion
What are the four muscles that move the pectoral girdle?
- Pectoralis major
- Pertoralis minor
- Subclavius
- Serratus anterior
What are the heads of the pectoralis major? What are the movements it creates?
- The pectoralis major is a large, fan-shaped muscle that covers the superior part of the thorax.
- It has clavicular and sternocostal heads. The sternocostal is much bigger
- Together, they produce powerful adduction and medial rotation of the arm
- The clavicular head flexes the humerus
- The sternocostal head extends it back from the flexed position
Which border of the pectoralis major makes up the most of the anterior wall of the axilla?
The lateral border
What muscles form the deltopectoral groove and later deltopectoral triangle? Why is this important?
The pectoralis major and the adjacent deltoid muscles form the narrow deltopectoral groove, in which the cephalic vein runs.
However, the muscles diverge slightly from each other superiorly and, along with the clavicle, form the clavicopectoral (deltopectoral) triangle.
How do you test the clavicular head of the pectoralis major?
The arm is abducted 90 degrees; the individual then moves the arm anteriorly against resistance. If moving normally, the clavicular head can be seen and palpated
How do you test the sternocostal head of the pectoralis major?
The arm is adducted 60 degrees and then adducted against resistance. If acting normally, the sternocostal head can be seen and palpated
Where is the pectoralis minor? What shape is it?
- It lies in the anterior wall of the axilla where it is almost completely covered by the pec major.
- It is triagular in shape.
- It’s base (proximal attachment) is attached to the 3rd-5th ribs near their costal cartilages
- It’s apex (distal attachment) is on the coracoid process of the scapula
What is the function of the pectoralis minor muscle?
- It stabilises the scapula and is used when stretching the upper limb forward to touch an object that is just out of reach
- It assists in elevating the ribs for deep inspiration when the pectoral girdle is fixed
- With the coracoid process, it forms a bridge under which vessels and nerves must pass to the arm.
Where is the subclavius? What is it’s function?
- The subclavius lies almost horizontally when the arm in is the anatomical position. This small, round muscle is located inferior to the clavicle.
- It afford some protection to the subclavian vessels and the superior trunk of the bracial plexus if the clavicle breaks
- The subclavius anchors and depresses the clavicle, stabilising it during movements of the upper limb
Where is the serratus anterior?
The serratus anterior overlies the lateral part of the thorax and forms the medial wall of the axilla.
The muscular strips pass posteriorly and then medially to attach to the whole length of the anterior surface of the medial border of the scapula, including its inferior angle.
What is the function of the serratus anterior?
- It is one of the most powerful muscles of the pectoral girdle.
- It is a strong protractor of the scapula and is used when punching or reaching anteriorly
- The strong inferior part of the muscle rotates the scapula, elevating it’s glenoid cavity so the arm can be raised above the shoulder
- It anchors the scapula, keeping it closely applied to the thoracic wall, enabling other muscles to use it as a fixed bone for movements of the humerus
How do you test the serratus anterior?
The hand of the outstretched limb is pushed against a wall. If the muscle is acting normally, several digitations of the muscle can be seen and palpated
What is the proximal attachment of:
* pectoralis major
* pectoralis minor
* subclavius
* serratus anterior
- Pectoralis major - clavicular head: anterior surface of medial half of the clavicle.
- sternocostal head: anterior surface of the sternum, superior six costal cartilages, - Pectoralis minor - 3rd-5th ribs near their costal cartilages
- Subclavius - junction of the 1st rib and it’s cartilage
- Serratus anterior - external surfaces of the lateral parts of 1st- 8th ribs
What is the proximal attachment of:
* pectoralis major
* pectoralis minor
* subclavius
* serratus anterior
- Pectoralis major - lateral lip of the intertubercular sulcus of the humerus
- Pectoralis minor - medial border and superior surface of coracoid process of scapula
- Subclavius - inferior surface of the middle third of the clavicle
- Serratus anterior - anterior surface of the medial border of the scapula
Where is the axilla? What is it’s function?
The axilla is the pyramidal space inferior to the glenohumeral joint and superior to the axillary fascia at the junction of the arm and the thorax.
The axilla provides a passageway, usually protected by the adducted upper limb, for the neurovascular structures that serve the upper limb.
What are the ways in and out of the axilla?
- Superiorly, via the cervico-axillary canal to (of from) the root of the neck
- Anteriorly via the clavipectoral triangle to the pectoral region
- Inferiorly and laterally to the limb itself
- Posteriorly, via the quadrangular space to the scapula region
- Inferiorly and medially along the thoracic wall to the inferiorly placed axio-appendicular muscles (serratus anterior and lattisumus dorsi)
Regarding the axilla, what makes up the apex?
Apex - cervico-axillary canal, the passageway between the neck and the axilla, bound by the 1st rib, the clavicle and superior edge of the scapula
Regarding the axilla, what makes up the base?
Base - axillary fossa formed by the concave skin, subcutaneous tissue, and axillary (deep) fascia extending from the arm to the thoracic wall. These are bound by the anterior and posterior axillary folds, thoracic wall and the medial aspect of the arm
Regarding the axilla, what makes up the anterior wall?
Anterior wall - has two layers, formed by the pec major and pec minor and the pectoral and clavicopectoral fascia associated with them. The anterior axillary fold is the inferiormost part of the anterior wall that may be grasped between the fingers; it is formed by the pectoralis major, as it bridges from the thoracic wall to the humerus
Regarding the axilla, what makes up the posterior wall?
Posterior wall - formed chiefly by the scapula and subscapularis on it’s anterior surface and inferiorly by the teres major and latissimus dorsi. The posterior lateral fold is the inferiormost part of the posterior wall that may be grasped. It extends further inferiorly that the anterior wall and is formed by latissimus dorsi and teres major.
Regarding the axilla, what makes up the medial wall?
Medial wall - formed by the thoracic wall (1st - 4th ribs and intercostal muscles) and the overlying serratus anterior
Regarding the axilla, what makes up the lateral wall?
Lateral wall - is a narrow bony wall formed by the intertubercular sulcus in the humerus
What does the axilla contain?
- Blood vessels - axillary artery and it’s branches, axillary vein and it’s tributaries
- Lymphatic vessels and groups of axillary lymph nodes
- Axillary fat
- Large nerves that make up the brachial plexus
What forms the breast?
Two thirds of the breast are formed by the pectoral fascia overlying the pectoralis major; the other third, by the fascia covering the serratus anterior.
What is the axillary process?
A small part of the mammary gland may extend along the inferior-lateral edge of the pec major towards the axillary fossa, forming an axillary process. Sometimes women get nervous, thinking this is a lump but it’s normal
Where are the mammary glands? How are they kept there?
They are firmly attached to the dermis of the overlying skin, especially by substantial skin ligaments, the suspensory ligaments. These condensations of fibrous connective tissue, particularly developed in the superior part of the gland, help support the lobes and lobules of the glands
What is the arterial supply of the breast?
It derives from the:
* Medial mammary branches of perforating branches and anterior intercostal branches of the internal thoracic artery, originating from the subclavian artery
* Lateral thoracic and thoraco-acromial arteries, branches of the axillary artery
* Posterior intercostal arteries, branches of the thoracic aorta in the 2nd, 3rd and 4th intercostal spaces
What is the venous drainage of the breast?
Mainly to the axillary vein, but there is some drainage to the internal thoracic vein
What is the lymphatic drainage of the breast?
Lymph passes from the nipple, areola, and lobules of the gland to the subareolar lymphatic plexus
From this plexus:
* Most lymph (>75%) especially from the lateral breast quadrants, drains to the axillary lymph nodes, initially to the anterior or pectoral nodes
* Most of the remaining lymph, particularly from the medial quadrants, drains to the parasternal lymph nodes or to the opposite breast, whereas lymph from the inferior quadrants may pass deeply to abdominal lymph nodes
The posterior shoulder muscles are divided into three groups. What are they?
- Superficial posterior axio-appendicular (extrinsic shoulder) muscles - trapezius and lattisimus dorsi
- Deep posterior axio-appendicular (extrinsic shoulder) muscles - levator scapulae and rhomboids
- Scapulohumeral (intrinsic shoulder) muscles - deltoid, teres major, and the four rotator cuff muscles (supraspinatus, infraspinatus, teres minor, and subscapularis)
Where is the trapezius and what is it’s general purpose?
The trapezius provides a direct attachment of the pectoral girdle to the cranium and vertebral column, and assists in suspending the upper limb.
It is a large, triangular muscle that covers the posterior aspect of the neck and the superior half of the trunk
The fibers of the trapezius are split into three parts, which have different actions. What are the parts and what are their actions?
- Descending fibres elevate the scapula
- Middle fibres retract the scapula (pull it posteriorly)
- Ascending (inferior) fibres depress the scapula and lower the shoulder
How do you test the trapezius?
Shrug the shoulder against resistance. If the muscle is working properly, the superior border can be easily seen and palpated
What are the proximal and distal attachments of the trapezius?
- Proximal attachment - posterior tubercles of the transverse processes of C1-C4 vertebrae
- Distal attachment - medial border of the scapula superior to the root of the scapular spine
What is the innervation and muscle action of the trapezius?
- Innervation - Dorsal scapula (C4, C5) and cervicle (C3, C4) nerves
- Muscle action - Elevate the scapula and rotates it’s glenoid cavity inferiorly by rotating the scapula
What is the function of the latissimus dorsi and what is it’s general location?
The large, fan-shaped muscle passes from the trunk to the humerus, and acts directly on the glenohumeral joint and indirectly on the pectoral girdle.
It extends, retracts and rotates the humerus medially e.g when folding your arms behind your back or scratching the opposite scapula. It is a powerful adductor of the humerus, it also raises the trunk to a superiorly raised arm so it important in climbing and pull-ups
How do you test the latissimus dorsi?
The arm is abducted 90 degrees and then adducted against resistance. If the muscle is normal, it can be seen and easily palpated in the posterior axillary fold
What is the proximal and distal attachment of the latissimus dorsi?
- Proximal attachment - spinous processes of inferior 6 thoracic vertebrae, thoraco-lumbar fascia, iliac crest and inferior 3 or 4 ribs
- Distal attachment - floor of intertubercular sulcus of humerus
What is the innervation and muscle action of the latissimus dorsi?
- Innervation - thoracodorsal nerve (C6, C7, C8)
- Muscle action - extends, adducts and medially rotates the humerus; raises body towards arms in climbing
Where is the levator scapulae?
The superior third of the levator scapulae lies deep to the sternocleidomastoid; the inferior third is deep to the trapezius.
From the transverse processes of the upper cervical vertebrae, the fibres pass inferiorly to the superomedial border of the scapula
What is the function and muscle action of the levator scapulae?
- It acts with the trapezius to elevate or fix the scapula.
- It acts with the rhomboids and pec minor to rotate the scapula, depressing the glenoid cavity.
- Acting bilaterally with the trapezius it extends the neck, acting unilaterally, it flexes the neck
What is the proximal and distal attachment and innervation of the levator scapulae?
- Proximal attachment - posterior tubercles of the transverse processes of C1-C4 vertebrae
- Distal attachment - medial border of scapula superior to the root of the scapula spine
- Innervation - Dorsal scapula (C4, C5) and cervical (C3, C4) nerves
What are the two rhomboids? Where are they? What is the difference between them?
- The rhomboids (major and minor) lie deep to the trapezius and pass inferolaterally from the vertebrae to the medial border of the scapula.
- The thin, flat rhomboid major is approximately two times wider than the thicker rhomboid minor lying superiorly to it.
What is the muscle action and innervation of the rhomboids?
- Muscle action - retract the scapula and rotate it’s glenoid cavity inferiorly; fix scapula to the thoracic wall
- Innervation - dorsal scapula nerve (C4, C5)
What are the proximal and distal attachments of the rhomboids?
- Proximal attachment - minor: nuchal ligament, spinous processes of C7 and T1 vertebrae - major: spinous processes of T2 - T5 vertebrae
- Distal attachment - minor: smooth triagular area at the medial end of the scapula spine - major: medial border of the scapula from level of the spine to inferior angle
How do you test the rhomboids?
The patient places his or her hands on their hips and pushes the elbows posteriorly against resistance. If acting normally, they should be able to be palpated along the medial borders of the scapulae
What muscles cause elevation of the scapula and what nerves innervate them?
- Trapezius - descending part (1) - spinal accessory (CN XI)
- Levator scapulae (2) and Rhomboids (3) - dorsal scapular
What muscles cause depression of the scapula and what nerves innervate them?
- Gravity (12)
- Pectoralis major (4) - pectoral nerves
- Latissimus dorsi (5) - thoracodorsal
- Trapezius, ascending part (6) - spinal accessory (CN XI)
- Serratus anterior, inferior part (7) - long thoracic
- Pectoralis minor (8) - medial pectoral
What muscles cause protraction of the scapula and what nerves innervate them?
- Serratus anterior (9) - long thoracic
- Pectoralis major (10) - pectoral nerves
- Pectoralis minor (11) - medial pectoral
What muscles cause retraction of the scapula and what nerves innervate them?
- Trapezius, middle part (11) - spinal accessory (CN XI)
- Rhomboids (3) - dorsal scapular
- Latissimus dorsi (5) - thoracodorsal
What muscles cause upward rotation of the scapula and what nerves innervate them?
- Trapezius, descending part (1) and ascending part (6) - spinal accessory (CN XI)
- Serratus anterior, inferior part (7) - long thoracic
What muscles cause downward rotation of the scapula and what nerves innervate them?
- Gravity (12)
- Levator scapulae (2) and rhomboids (3) - dorsal scapular
- Latissumus dorsi (5) - thoracodorsal
- Pectoralis minor (8) - medial pectoral
- Pectoralis major, inferior sternocostal head (4) - medial and lateral pectoral nerves
What is the scapular anastamosis and why is it important?
It is a system containing certain subclavian arteries and their corresponding axillary arteries, forming a ciculatory anastamosis around the scapular.
It means that if the axillary artery is cut or ligated, an adequate collateral blood supply will arrive to the arm via the dorsal scapular artery, and it’s anastamosis with the circumflex scapular artery.
What is the quadrangular space?
It is an anatomical space in the posterior axilla region.
It provides a conduit for structures to pass between the axilla and the posterior compartment of the arm
What are the borders of the quadrangular space?
It is rectangular space with four boundaries:
* Superior - inferior margin of the teres minor
* Lateral - surgical neck of the humerus
* Medial - long head of triceps brachii
* Inferior - superior aspect of teres major
What travels through the quadrangular space?
It contains the axillary nerve and posterior circumflex humeral artery and vein as they travel into the posterior upper arm
What the triangular space?
It is a space located in the axilla. It allows structures to pass between the axilla and posterior scapula region.
What are the borders of the triangular space?
The triangular space is orientated with the base laterally and the apex medially. It has three borders:
* Lateral - medial margin of the long head of the triceps brachii
* Inferior - superior margin of the teres major
* Superior - inferior border of the teres minor or the subscapularis
What travels through the triangular space?
It is a passageway that allows structures to travel between the axilla and posterior scapula region.
It contains the circumflex scapular artery and vein
What muscles attach to the coracoid process?
- Pectoralis minor
- Coracobrachialis
- Short head of the biceps brachii
What ligaments attach to the coracoid process?
Coracoclavicular ligament
Coraco-acromial ligament
Coracohumeral ligament
Glenocoracoid ligament
What are the muscle attachments to the intertubercular groove?
Teres major
Latissimus Dorsi
Pectoralis major
It also makes up the lateral wall of the axilla
What muscles are in the anterior compartment of the forearm? What nerve are they supplied by? What is their arterial supply?
Biceps brachii
Brachialis
Coracobrachialis
They are all innervated by the musculocutaneous nerve and blood is supplied via muscular branches of the brachial artery
What muscles are in the posterior compartment of the forearm? What nerves are they supplied by? What is their arterial supply?
Triceps brachii - with three heads
Anconeus
Innervated by the radial nerve.
Blood supplied by profunda brachii artery
Where do the biceps brachii heads attach proximally and where do they merge?
The two heads of the biceps arise proximally by tendinous attachments to processes of the scapula, their fleshy bellies uniting just distal to the middle of the arm
Where does the biceps brachii attach distally?
However many heads there are, one single biceps tendon forms distally and attaches primarily to the radius
What joints can the biceps brachii move?
1) Glenohumeral joint
2) Elbow joint
3) Radio-ulnar joint
It primarily acts on the elbow and radio-ulnar joint
The action and effectiveness of the biceps brachii are markedly affected by the position of the elbow and the forearm. How does it vary?
- When the elbow is extended, the biceps is a simple flexor of the forearm
- When elbow flexion approaches 90 degrees and the forearm is supinated, the biceps is most efficient in producing flexion
- When elbow flexion approaches 90 degrees and the forearm is pronated, the biceps is the primary supinator of the forearm (e.g. a screwdriver or cork screw type action).
- When the forearm is pronated, the biceps barely acts as a flexor, even against resistance
What ligament converts the intertubercular groove into the intertubercular canal?
The transverse humeral ligament passes from the lesser to the greater tubercle of the humerus and converts the intertubercular groove into the intertubercular canal.
It holds the long head of the biceps in place.
Distally, where does the biceps tendon attach?
The major attachment of the biceps is to the radial tuberosity via the biceps tendon
What triangular membraneous band passes obliquely over the brachial artery and nerve to protect them at the ACF and lessens pressure on the biceps tendon during pronation and supination?
Where does it run?
The bicipital aponeurosis runs from the biceps tendon across the cubital fossa, and merges with the deep antebrachial fascia covering the flexor muscles in the medial side of the forearm.
It attached directly by means of the fascia to the subcutaneous border of the ulnar.
How do you test the biceps brachii?
The elbow joint is flexed against resistance when the forearm is supinated
What is the innervation of the biceps?
Musculocutaneous nerve (C5, C6, C7)
What are the distal and proximal attachments of the brachialis?
- Proximal - distal half of anterior surface of the humerus
- Distal - Coronoid process and tuberosity ulnar
What is the muscle action of the brachialis?
It is the main flexor of the forearm - it is the only pure flexor and therefore is strongest.
It flexes the arm in all positions
What is the innervation of the brachialis?
Musculocutaneous nerve (C5, C6, C7) and radial nerve (C5, C7)
What and the proximal and distal attachments of the coracobrachialis?
- Proximal - tip of coracoid process of scapula
- Distal - middle third of medial surface of the humerus
What is the innervation of the coracobrachialis?
Musculocutaneous nerve (C5, C6, C7)
What is the muscle action of the coracobrachialis?
- Helps flex and adduct the arm
- Resists dislocation of the shoulder. With the deltoid and long head of the triceps, it acts as a shunt muscle, resisting downward dislocation when carrying heavy things
The coracobrachialis is a useful landmark for locating other structures in the arm. Which structures and why?
- The musculocutaneous nerve pierces it (and can sometimes be squished by it)
- The distal part of it’s attachment indicates the location of the nutrient foramen of the humerus
What are the three heads of the triceps brachii? What are their roles?
- The long head crosses the glenohumeral joint, so helps the triceps stabilise the adducted glenohumeral joint by serving as a shunt muscle, resisting inferior dislocation. It also aids in extension and adduction of the arm, but is the least active head.
- The medial head is the workforce of forearm extension, active at all speeds and in the presence or absence of resistance.
- The lateral head is the strongest but is recruited primarily against resistance
Where is the subtedinous olecranon bursa?
Just proximal to the distal attachment of the triceps, between the triceps tendon and olecranon
How do you test the triceps?
The arm is abducted to 90 degrees, and then the flexed forearm is extended against resistance
What is the innervation of the triceps?
Radial nerve (C6, C7, C8)
What are the proximal and distal attachments of the anconeus?
- Proximal - lateral epicondyle of the humerus
- Distal - lateral surface of the olecranon and superior part of the posterior surface of ulna.
What is the muscle action of the anconeus?
Assists triceps in extending forearm
Stabilises elbow joint
May adduct ulna during pronation
What is the innervation of the anconeus?
Radial nerve (C7, C8, T1)
What four muscles make up the rotator cuff muscles?
- Supraspinatus
- Infraspinatus
- Teres minor
- Subscapularis
Why are the rotator cuff muscles called the rotator cuff muscles?
Because they form a musculotendinous rotator cuff around the glenohumeral joint.
All except from the supraspinatus are rotators of the humerus
Apart from the rotator cuff muscles, what also helps form the rotator cuff?
The tendons of the SITS muscles blend with and reinforce the fibrous layer of the joint capsule of the glenohumeral joint, thus forming the rotator cuff that protects the joint and gives it stability.
The tonic contractions of the contributing muscles holds the relatively large head of the humerus in the small, shallow glenoid cavity
What are the proximal and distal attachments of the supraspinatus?
- Proximal - supraspinous fossa of scapula
- Distal - superior facet of greater tubercle of the humerus
What is the innervation of the supraspinatus?
Suprascapular nerve (C4, C5, C6).
Initiates and assists the deltoid in abduction of arm and acts with rotator cuff muscles
What are the proximal and distal attachments of the infraspinatus?
- Proximal - infraspinous fossa of scapula
- Distal - middle facet of greater tubercle of humerus
What is the innervation and muscle action of the infraspinatus?
Suprascapular nerve (C5, C6).
It laterally rotates the arm and acts with the rotator cuff muscles
What are the proximal and distal attachments of the teres minor?
- Proximal - middle part of the lateral border of the scapula
- Distal - inferior facet of the greater tubercle of the humerus
What is the innervation and muscle action of the teres minor?
Axillary nerve (C5, C6)
It laterally rotates the arm and acts with the rotator cuff muscles
What are the proximal and distal attachments of the subscapularis?
- Proximal - subscapular fossa, most of the anterior surface of the scapula
- Distal - lesser tubercle of the humerus
What is the innervation and muscle action of the subscapularis?
Upper and lower subscapular nerves (C5, C6, C7)
It medially rotates the arm, acts as part of the rotator cuff muscles
How do you test the supraspinatus?
Abduction of the arm is attempted from the fully adducted position against resistance
How do you test the infraspinatus?
The person flexes the elbow and adducts the arm. The arm is then laterally rotated against resistance
