Anatomy Flashcards
Torso/Trunk
The main central part of the body including the thorax, abdomen, and pelvis.
Not including the neck, head, or the upper or lower limbs.
Thorax
The upper part of the torso from the bottom of the neck to the diaphragm (an internal muscular sheet that separates the thorax from the abdomen).
The thorax houses the lungs and heart and is surrounded by the ribs.
The term ‘chest’ refers to the front of the thorax only.
Abdomen
The central part of the torso between the diaphragm and top of the pelvic bones.
The abdomen contains most of the organs of digestion including the stomach, intestine, and liver.
In everyday conversation, people often refer to the entirety of the abdomen as the ‘stomach’.
Pelvis
The lowest part of the torso, between the abdomen and the start of the lower limbs.
The pelvis contains the last part of the digestive tract, the bladder, and reproductive organs.
The bony ‘ring’ of the pelvic region is also called the pelvis, so the term ‘pelvis’ is used to describe both the entirety of the pelvic region (including organs and blood vessels etc.) and the bone of the pelvic region.
Back
A poorly descriptive term.
Anatomically, the ‘back’ refers to the entire posterior surface of the torso.
Arm
The upper part of the upper limb (from the torso to the elbow).
This is where the biceps muscle is located.
Forearm
The middle part of the upper limb (from the elbow to the wrist).
Thigh
The upper part of the lower limb (from the pelvis to the knee).
Leg
The middle part of the lower limb (from the knee to the ankle)
anatomical position
A person is standing up with their feet flat on the floor, facing forward, arms by their sides with their palms facing forwards
Diagram page 9
Superior
Above
Example; The brain is superior to the heart
Inferior
Below
Example; the pelvis is inferior to the pelvis
Anterior/ Ventral
Front (in front of)
Example; The nose is anterior to the ears
Posterior/dorsal
Back (behind)
Example; the spine is posterior to the sternum
Medial
Closer to the centre line
Example; the big toe is medial to the little toe
Lateral
Further away from the centre line
Example; The thumb is lateral to the palm
Proximal
Closer to the origin
Example; The elbow is proximal to the wrist (wrist is the origin here)
Distal
Further away from the origin
Example; the toes are distal to the knee (origin is the knee here)
Ipsilateral
The same side of the body
Example; The right arm and left leg are contralateral to each other.
Deep
Further away from the surface
Example; The heart is deep to the sternum.
Superficial
Closer to the surface
Example; The skin is superficial to the muscle
Supine (position)
Lying down, flat on back, facing up
Example; With the patient supine, they are facing the ceiling.
Prone (position)
With the patient prone, they are facing the floor
Cranial
Towards the head
Example; the brain is cranial to the spina cord
Caudal
Towards the tail
Example; The pelvis is caudal to the abdomen.
Rostral
Towards the face
Example; The frontal lobe of the brain is rostral to the occipital lobe.
Coronal (/frontal)
face-on’. A coronal incision cuts a structure into an anterior and a posterior part.
Diagram page 12
Sagittal
‘side-on’.
A midline sagittal incision cuts a structure into a left and a right side.
Parasagittal
a cut in the sagittal plane but parallel to the midline (i.e. off to one side or the other)
Axial (also called transverse or horizontal)
end-on
An axial incision cuts a structure into a superior and an inferior part.
The skeleton (diagram page 13)
bony scaffolding of the body
Axial part of skeleton
central, or core, parts: the skull, vertebral column, ribs, and sternum
Appendicular part of skeleton
the bones of the limbs, including the shoulder blades
(scapulae), collarbones (clavicles) and the pelvic girdle
A joint
formed where two bones meet; the two bones articulate with each other
Not all joints move
How are joints classified?
according to their histological structure and their biomechanical structure
‘histological’ refers to the cellular and structural composition of tissue
Three different histology all types of joints (diagrams page 15-16)
Synovial
Fibrous
Cartilaginous (primary Cartilaginous and secondary Cartilaginous)
Synovial joints
Most common type of joint
A very narrow synovial cavity separates the articular surfaces of the bones.
The cavity contains lubricating synovial fluid, which is enclosed in a joint capsule.
The joint capsule has two layers: an outer fibrous capsule, and an inner synovial membrane.
The articular surfaces are covered with articular ‘hyaline’ cartilage
Synovial joints usually allow a great deal of movement.
Examples of synovial joints
Shoulder joint
Knee joint
Wrist joint
Fibrous joint
connect two bones together via strong fibrous tissue
There is no cavity and no fluid
There is usually very little (if any) movement at fibrous joints.
Examples of fibrous joints
the joints between the individual bones of the skull (called ‘sutures’).
Cartilaginous joints
like fibrous joints, but the articular surfaces are separated by cartilage instead of fibrous tissue
There are two types; primary and secondary
Primary cartilaginous joints
are connected to each other by hyaline cartilage, which allows some flexibility
Examples of Primary cartilaginous joints
where the ribs meet the sternum
Secondary cartilaginous joints
are connected to each other by fibrocartilage, plus a layer of hyaline cartilage covers the articular surfaces of the bones.
They are flexible but strong and can support a lot of weight.
Examples of Secondary cartilaginous joints
the intervertebral discs (between the vertebrae in the spine)
How are synovial joints biochemically classified?
Synovial joints permit movements in different planes and to different degrees, depending on the shape of the articular surfaces and other factors such as surrounding ligaments and muscles
6 types of synovial joints (diagram on page 18)
Ball and socket
Hinge
Pivot
Saddle
Condyloid
Plane
Ball and socket joint
the end of one bone is shaped like a ball and the end of the other bone is shaped like a bowl that the ball fits inside
These joints are mobile and allow a significant range of movement in all directions, including rotation
How mobile and stable these joints are depends on the fit between the ball and socket - the better the fit, the more stable the joint but the less mobile it is
With a poorer fit comes better mobility but less stability and greater risk of dislocation
Examples
Hip
Jaw
Shoulder
Hinge joint
they allow a significant range of movement, but only in one plane
Examples
In the fingers
Elbow
Knee
Pivot joint
It allows rotational movement only
Example
found at the top of the spine where the first and second vertebrae articulate with each other
The first vertebrae (C1, the atlas) at the base of the skull pivots around the peg of the second vertebrae (C2, the axis)
Allows us to turn our head left and right
Saddle joint
joints are shaped like a rider sitting in a saddle, and permit movement in two planes
Examples
the joint at the base of the thumb, where the metacarpal of the thumb articulates with one of the small carpal bones (the carpometacarpal joint of the thumb)
Condyloid joint
like a ball and socket joint, but the joint surfaces are oval- shaped.
They have a good range of movement but only in two planes
Examples
the wrist joint
The metacarpophalangeal joints of the fingers (the knuckles)
Plane joint
the articular surfaces are almost flat and glide against each other.
The range of movement is usually limited and dictated by the neighbouring bones and surrounding ligaments.
Examples
the joints between the small bones of the wrist
the acromioclavicular joint at the top of the shoulder
Ligament
A band of fibrous connective tissue that attaches bone to bone.
Ligaments stabilise joints and limit their movement.
They can stretch and, over time, can be stretched to allow greater joint mobility.
double- jointed
People who have ligaments that are stretchy enough to allow their joints a greater degree of mobility (‘hypermobility’)
A sprain
occurs when a ligament is overstretched and injured.
The most often sprained ligaments are those of the ankle, caused by ‘going over’ on the ankle (forced, excessive inversion).
Over-stretched and torn ligaments are painful. They may not return to their original shape.
When joints dislocate the ligaments may be stretched so much that they become permanently lax, leading to joint instability and in some cases, recurrent dislocation.
Flexion
Bending (decreasing the angle between the two parts)
Extension
Straightening (increasing the angle between the two parts
Lateral flexion
Unique to the vertebral column: bending sideways.
Abduction
Movement away from the midline
Adduction
Movement towards the midline
Internal rotation
Rotating (around an axis) towards the midline (also known as medial rotation)
External rotation
Rotating (around an axis) away from the midline (also known as lateral rotation)
Pronation
Unique to the forearm: internal rotation of the radius, so that the palm faces posteriorly (our forearm and hand are prone when we type using a keyboard)
Supination
Unique to the forearm: external rotation of the radius, so that the palm faces anteriorly (i.e. the anatomical position)
Opposition
Unique to the thumb and little finger: flexion and rotation of the thumb or little finger so that each one can reach the other
Circumduction
Combination of flexion, extension, abduction, and adduction such that the appendage traces a circular or conical pattern.
Dorsiflexion
Unique to the ankle: the foot and toes move superiorly towards the shin (pointing the foot and toes ‘up’)
Plantarflexion
Unique to the ankle: the foot and toes move inferiorly (pointing the foot and toes ‘down’).
Inversion
Unique to the foot and ankle: medial flexion so that the sole of the foot faces medially
Eversion
Unique to the foot and ankle: lateral flexion so that the sole of the foot faces laterally
Protraction
Unique to the scapula and mandible: moving the scapula or mandible anteriorly (e.g. moving our upper limb out in front of us to push open a door
Retraction
Unique to the scapula and mandible: moving the scapula or mandible posteriorly (e.g. ‘squaring’ the shoulders)
Elevation
Unique to the scapula and mandible: moving the scapula or mandible superiorly (e.g. shrugging the shoulders, closing the mouth)
Depression
Unique to the scapula and mandible: moving the scapula or mandible inferiorly (e.g. returning the shoulders after elevation, opening the mouth).
How are muscles classified?
Histologically according to their cellular and structural composition
Three different types of muscle
Skeletal
Smooth
Cardiac
Skeletal muscle
found throughout the body
Skeletal muscles provide support for the body and move the joints and some soft tissues.
They are under voluntary control (i.e. we can consciously control them).
The muscle fibres are described as striated as they have a striped appearance under a microscope.
Examples
the eyeball
tongue
Smooth muscle
located in the walls of blood vessels and internal organs
Smooth muscle is involuntarily controlled by the autonomic nervous system – we cannot consciously control its activity.
Smooth muscle fibres are not striated.
Examples
Intestine
Cardiac muscle
Unique to the heart
It is involuntarily controlled. Cardiac muscle cells contract in response to electrical impulses that are spontaneously generated by specialised cells within the heart. The autonomic nervous system influences these specialised cells and can speed up or slow down the heart rate.
Cardiac muscle fibres are striated.
Tendons
Attach skeletal muscles to bone or soft tissues
What are tendons composed of?
Strong connective tissue
Aponeuroses
Thin, flat sheets formed by tendons
Found in the scalp and abdominal wall
Tendons can also be…
Rounded
‘Belly’
The muscle between the tendons
How are joints moved?
muscles or tendons must cross the joints
When a muscle contracts, one of its attachments moves whilst the other attachment does not.
The bone or part that does not move is called the origin, and the bone or part that does move is called the insertion.
Brevis
Means short
Shapes of Skeletal Muscles- The fibres of skeletal muscles are arranged in various ways to allow them to exert force or achieve specific movements.
Parallel- fusiform and Strap
Convergent
Circular
Pinnate- unipennate, Biden ate, multipennate
Parallel
the fibres are aligned parallel to each other
They can shorten significantly and quickly but are relatively less powerful than pennate muscles.
There are two subtypes: fusiform and strap
Fusiform
Muscles often have a long tendon at each end, and the muscle belly bulges out in the middle.
Example: biceps brachii
Strap
Muscles are belt-shaped and relatively uniform in width at the belly.
Examples:
sartorius in the thigh
rectus abdominis in the abdominal wall.
Convergent
these muscles are fan-shaped and have a very broad attachment at one end, with fibres converging onto a much smaller attachment at the other
Example: pectoralis major on the anterior chest wall.
Circular
the fibres are arranged in concentric rings around a structure and are often called sphincters.
When they contract, they close the aperture they surround.
Example: the muscles around the eyes and lips.
Pennate
the fibres are arranged at an angle to the direction in which the muscle acts.
They cannot shorten as much as parallel muscles, but they are powerful.
There are three subtypes: unipennate, bipennate, multipennate
Unipennate
the fibres are arranged diagonally in relation to the tendon and insert onto one side of the tendon only (like a feather but with fibres on only one side of the central spine)
Example: extensor digitorum longus in the leg
Bipennate
the fibres are arranged in a V-shape and insert onto both sides of the tendon; they look like a feather.
Example: rectus femoris in the thigh.
Multipennate
these muscles look like multiple bipennate muscles (or multiple feathers) side-by-side, all attaching onto one tendon.
Example: deltoid in the shoulder.
A motor unit
is composed of a single motor neuron, its axon, and the muscle fibres it supplies.
There is great variation in the size of motor units.
In the small muscles (that move the eyeball)…
a single motor nerve axon may only supply just a few muscle fibres, allowing fine control of eye movements.
In the larger thigh muscles…
a motor unit may comprise thousands of muscle fibres, giving the muscle power, but less precision
Three parts that the upper limb and lower limb are composed of…
Upper limb: arm, forearm, hand
Lower limb: thigh, leg, foot
Bones and joints are smaller and more numerous in the distal parts of the limbs
Diagram page 25
The gross anatomy of the upper and lower limbs is very similar. We find:
● a ball and socket joint where the limb meets the torso (the shoulder and hip joints).
● one large bone in the proximal part (humerus and femur).
● a hinge joint separates the proximal and middle parts (elbow and knee joints).
● two bones in the middle part (radius and ulna, tibia and fibula).
● a collection of small bones at the start of the distal part (carpal bones, tarsal
bones).
● five digits (fingers and toes).
● one digit significantly larger than the others (thumb, great toe).
● most of the muscle mass concentrated proximally (arm and thigh).
The upper limb has evolved primarily for dexterity and therefore is more mobile:
● the shoulder joint has a shallow socket and relatively lax ligaments which allow
a significant range of motion for positioning the hand
● the fingers are long and perform complex movements.
the lower limb has evolved for bipedal locomotion and to support the weight of the body:
● the hip joint has a deep socket and strong ligaments, so it is very stable but less mobile than the shoulder joint
● the foot and toes are adapted for weight-bearing rather than dexterity.
The Vertebral Column/spine/spinal column
spans from the base of the skull to the coccyx.
The spine supports the head, neck, and torso, protects the spinal cord, provides an attachment for muscles, and allows movement
Diagram on page 26
There are 33 vertebrae divided into 5 ‘sections’:
Diagram on page 28
Cervical
Thoracic
Lumbar
Sacral
Coccygeal
Cervical
7 cervical vertebrae in the neck (C1 - C7)
Thoracic
12 thoracic vertebrae in the thorax (T1 - T12)
Lumbar
5 lumbar vertebrae in the abdomen (L1 - L5)
Sacral
5 sacral vertebrae in the pelvis (S1 - S5) which are fused into the sacrum
Coccygeal
4 coccygeal vertebrae in the pelvis (Co1 - Co4) which are fused into
the coccyx.
Why is the vertebral column curved rather than straight?
Helps to absorb shock
Eg; when jumping
cervical lordosis and a lumbar lordosis
Formed by the cervical and lumbar segments being curved anteriorly
thoracic kyphosis and a sacral kyphosis.
Formed by the thoracic and sacral segments curving posteriorly
How is the vertebrae joint together?
Small synovial facet joints, intervertebral discs, and several groups of ligaments connect the vertebrae to each other.
Intervertebral discs between the vertebrae support the weight of the upper body and absorb shock.
Movements between individual vertebrae are small, but collectively allow the vertebral column significant movement.
Projections
Named parts of the vertebra (they all have similar shapes)
Facets
Required for articulation (joins) with adjacent vertebrae
Nerves
Axons bundled together
The nervous system operates on three levels
conscious level
voluntary level
unconscious, involuntary level
Cranial
Head end
Caudal
Tail end
Relates to embryological development
Rostral
Towards the face
Relates to embryological development
Positioning of the brain, Rostral and caudal
When we talk about the brain, rostral is anterior and caudal is posterior.
When we talk about the spinal cord, the more superior part is rostral, and the more inferior part is caudal.
The nervous system is anatomically subdivided into two
● the central nervous system (CNS) = brain and spinal cord
● the peripheral nervous system (PNS) = all nervous tissue outside the CNS, primarily nerves:
● cranial nerves (arise from the brain)
● spinal nerves (arise from the spinal cord)
● autonomic nerves
Functionally, the nervous system is subdivided into two parts:
● Somatic nervous system = controls voluntary activities; under conscious control.
● Autonomic nervous system (ANS) = controls involuntary activities; not under conscious control.
The brain is protected by the skull and is anatomically divided into three main parts:
● the cerebrum
● the cerebellum
● the brainstem
The Cerebrum
is the largest part of the brain.
It is composed of masses of neurons and other cells that support them.
● It is composed of the left and right cerebral hemispheres, which are connected to each other
● The surface of the cerebrum is called the cerebral cortex. It contains neuron cell bodies, which gives it a grey appearance, hence the term grey matter. Information is processed in the grey matter.
● The cerebral cortex is folded. The folds are called gyri (singular: gyrus), and the grooves between the folds are called sulci (singular: sulcus).
Deep to the cerebral cortex, within the cerebral hemispheres, we find:
● masses of axons. They have a pale appearance in comparison to the cortex and collectively comprise white matter. Information is transmitted through bundles of fibres in the white matter.
● collections of cell bodies called nuclei. They look grey in comparison to the surrounding white matter (nucleus = a collection of cell bodies in the CNS).
4 lobes that each cerebral hemisphere is divided into anatomically (named after the bones of the skull)
frontal
parietal
occipital
temporal lobes
Anatomical illustration of the lobes
The large frontal lobe lies anteriorly, and the small occipital lobe lies posteriorly.
The parietal and temporal lobes lie between the frontal and occipital lobes.
Define The Cerebellum
Meaning ‘little brain’, the cerebellum lies inferior to the posterior part of the cerebrum
Features about the cerebellum
● is composed of left and right hemispheres that are connected to each other
● has a highly folded cortex
● contains white matter and nuclei deep to the cortex
The cerebellum is attached to the brainstem. The cerebellum functions in balance, coordination, and movement, but operates beyond our conscious control.
The brainstem’s three parts
the midbrain
pons
Medulla
Where is the brainstem located
It lies inferior to the cerebrum and anterior to the cerebellum (and is attached to both)
Vital functions of the brainstem
● it relays information between the cerebrum, spinal cord and cerebellum
● it gives rise to most of the cranial nerves
● it contains ‘centres’ that regulate breathing and consciousness.
The spinal cord
The spinal cord is continuous with the medulla of the brainstem and is protected by the vertebral column.
The spinal cord is shorter than the vertebral column; the cord ends around the level of L1 – L2.
The neuronal cell bodies that lie within the cord constitute the grey matter, which is roughly shaped like an ‘H’ in an axial cross-section. The grey matter is surrounded by white matter which contains tracts
Tracts: bundles of axons that connect different parts of the CNS to each other.
Tracts in the spinal cord cannot be seen with the naked eye.
How many spinal nerves are attached to the spinal cord?
31
Each pair of nerves corresponds to a spinal cord segment, and they carry information between the cord (CNS) and periphery (e.g. skin, muscles).
Ventricles
The brain is not completely solid but has cavities inside it called ventricles.
The ventricles are continuous with each other and filled with cerebrospinal fluid (CSF)
What produces cerebrospinal fluid?
Specialised cells within the ventricles
CSF leaves the ventricles through small openings and surrounds the brain and spinal cord.
The functions of the CSF:
● provides nutrients to the brain
● protects the brain by providing a cushion against trauma
● prevents delicate nerves and vessels from being compressed between the brain and the internal surface of the skull.
There are 4 interconnected ventricles within the brain
There’s a narrow, CSF-filled channel within the spinal cord
How many membranes lie between the brain and spinal cord and the bones that protect them?
3
What are these three membranes collectively called?
Meninges
What are the names of the 3 meningeal layers?
Dura mater
Arachnoid mater
Pia mater
Dura Mater
The dura mater lines the inner surface of the skull and vertebral column.
It is thick and strong.
Arachnoid mater
The arachnoid mater lies deep to the dura.
It is thin and loosely encloses the brain and spinal cord.
Pia mater
The pia mater lies deep to the arachnoid. It is adhered to the surface of the brain and spinal cord.
It is very thin and cannot be seen with the naked eye.
What is the function of the meninges?
● protect the brain
● provide a scaffold for blood vessels
Which 2 pairs of arteries supply the brain?
the left and right internal carotid arteries
the left and right vertebral arteries
Where are both these arteries found?
Both pairs of arteries ascend through the neck to the brain.
On the inferior surface of the cerebrum these arteries give rise to branches that form an interconnected ring called the Circle of Willis
The Circle of Willis is an example of an anastomosis - where branches from otherwise separate arteries unite with each other
Why is this type of blood supply beneficial?
theoretically allows for the blood supply to an area to be maintained if one of the vessels supplying it becomes blocked
Structure of Circle of Willis
The Circle of Willis gives rise to three cerebral arteries on each side (which supply the cerebral hemispheres), cerebellar arteries (which supply the cerebellum), and arteries that supply the brainstem and spinal cord.
Communicating arteries connect the cerebral arteries with each other.
Why does each artery supply a particular region, or territory, of the brain, or brainstem?
Because different regions of the brain serve different functions, the functional deficits seen when an artery is blocked is dependent on which artery is involved (blockage of an artery leading to death of brain tissue is called a stroke).
Veins function
Veins drain blood from the brain. There are deep veins within the brain and superficial veins on the surface of the brain.
There are also large veins enclosed within the dura mater called dural venous sinuses.
How is the nervous system subdivided?
Somatic nervous system
Automatic nervous system
What is the function of the somatic nervous system?
Controls voluntary activities
It has a motor and sensory component:
● The motor component controls the voluntary contraction of skeletal muscle. For example, it controls the movement of our limbs, trunk, and face.
● The sensory component sends information about peripheral stimuli from the sensory receptors in the body to the CNS, which reaches our conscious perception (e.g. touch, pain, temperature).
What does the automatic nervous system control?
Controls involuntary activities such as heart rate, blood pressure, respiration, digestion, and sexual arousal.
The ANS has a motor and sensory component.
The motor component of the ANS controls smooth muscle, glands, and cardiac muscle. It is subdivided into two parts:
● The sympathetic nervous system = ‘flight and fight’
● The parasympathetic nervous system = ‘rest and digest’
The sensory component of the ANS conveys sensory information about the internal environment from the viscera (organs) to the CNS, but it does not reach our conscious perception. An example is blood pressure monitoring.
What are the Sympathetic and parasympathetic nerves?
They are motor to smooth muscle, glands, and cardiac muscle.
They are also called visceral efferent nerves, as they leave the CNS and travel to the periphery.
They have generally opposite, but coordinated actions.
What does the sympathetic body prepare the body for?
Prepares the body for the four F’s: ‘fight, fright, flight, and freeze’:
● Heart rate increases and the bronchi dilate. Peripheral blood vessels constrict and divert blood away from the skin and gut to the skeletal muscles in preparation for activity.
The pupils dilate, hair stands on end and sweat glands are stimulated.
What does the parasympathetic body prepare the body for?
Prepares the body for ‘rest and digest’:
● Heart rate decreases and the bronchi constrict. Glands are stimulated (e.g. salivary glands, digestive secretions) and gut activity (peristalsis) is stimulated.
The pupils constrict.
Similarities and differences between both systems
The sympathetic and parasympathetic systems share the same basic anatomical arrangement, but with some important differences.
In both systems, there are two neurons in the pathway from the CNS to the target organ (effector).
The cell bodies of the first neurons lie in the CNS:
(Diagrams in booklet)
● Sympathetic neuron cell bodies lie in the thoracic and upper lumbar segments of the spinal cord (T1 - L2/3).
● Parasympathetic neuron cell bodies lie in the brainstem and sacral spinal cord (S2 - S4).
● Their axons leave the CNS and synapse with a second neuron, whose cell body lies in a ganglion (a collection of cell bodies outside the CNS)
● For this reason, the first neuron is called a preganglionic or presynaptic neuron, and the second neuron is called a postganglionic or postsynaptic neurone
● The postganglionic fibres travel to target organs.
Sympathetic ganglia
Lie closer to the CNS than to target organs, so their preganglionic axons are short, and their postganglionic axons are long.
Parasympathetic ganglia
Lie very close to target organs (or even within them) so their preganglionic axons are long, and their postganglionic axons are short.
Although both systems innervate the thoracic, abdominal, and pelvic viscera, the sympathetic system is far more widely distributed than the parasympathetic system.
Because sympathetic nerves innervate sweat glands and smooth muscle in the blood vessel walls and hair follicles (the arrector pili muscles), they reach every part of the body.
The sensory component of the autonomic nervous system conveys sensory information from the viscera to the CNS, but it does not usually reach our conscious perception.
Sensory autonomic fibres are also called visceral afferent fibres, as they convey information from the viscera back to the CNS.
They monitor our internal environment (e.g. blood pressure, levels of oxygen and carbon dioxide in our blood) and send information back to the CNS.
These sensory inputs elicit reflex (automatic, unconscious) responses, which constantly maintain our internal environment.
Visceral afferents also convey information to the CNS about distension, stretch, spasm or ischaemia of the viscera, which may cause pain or discomfort that does reach consciousness.
Visceral afferents travel back to the CNS along the paths of the sympathetic and parasympathetic nerves.
The distribution and course of visceral afferents is clinically important and relevant to the phenomenon of referred pain.
Cranial nerves
Arise from the cerebrum and brainstem.
There are twelve pairs which are numbered I - XII (roman numerals are always used) and individually named.
Their names are descriptive and relate to the nerve’s function, course, or structure(s) it supplies
The brainstem contains collections of cell bodies associated with the cranial nerves called cranial nerve nuclei (singular = nucleus)
Cranial nerves leave the CNS and travel into the periphery, so they are part of the peripheral nervous system.
The 12 cranial nerves mainly serve the head and neck.
Cranial nerves exit the skull by passing through holes in the base of the skull called foramina (singular = foramen)
The cranial nerves carry different types of nerve fibres.
Some cranial nerves are purely sensory, and some are purely motor.
Some cranial nerves carry both sensory and motor information. In addition, some cranial nerves carry parasympathetic fibres.
How many pairs of spinal nerves are attached to the spinal cord?
31
A pair of spinal nerves corresponds to each segment of the spinal cord. We have:
● 8 cervical spinal nerves (C1 - C8)
● 12 thoracic spinal nerves (T1 - T12)
● 5 lumbar spinal nerves (L1- L5)
● 5 sacral spinal nerves (S1 - S5)
● 1 coccygeal spinal nerve (Co1)
We have eight cervical spinal cord segments and pairs of spinal nerves, but only seven cervical vertebrae
The spinal nerves are mixed nerves and carry:
● somatic motor fibres from the CNS to the body
● sympathetic (i.e. autonomic motor) fibres from the CNS to the body
● somatic sensory fibres from the body into the CNS
The vertebral column protects the spinal cord.
Spinal nerves pass through the gaps formed between adjacent vertebrae, the intervertebral foramina
Somatic Motor Fibres
The cell bodies of the motor neurones lie in the ventral horn of the spinal cord (grey matter).
The axons leave the cord via a series of rootlets, which merge to form the ventral (motor) root of the spinal nerve.
These motor fibres stimulate the voluntary contraction of skeletal muscle.
Somatic Sensory Fibres
The cell bodies of peripheral sensory neurons lie in the dorsal root ganglia (DRG) which are visible with the naked eye as small ‘swellings’ on the dorsal roots.
Instead of a single axon, these neurons have two processes, one that projects peripherally into the spinal nerve and one that projects centrally into the dorsal horn of the spinal cord (grey matter)
Sensory information travels from peripheral receptors (e.g. in the skin) towards the DRG via the spinal nerve and then from the DRG to the dorsal horn via a series of rootlets.
Sympathetic fibres
All 31 pairs of spinal nerves contain sympathetic fibres, which stimulate sweat glands and the contraction of smooth muscle in peripheral blood vessels and the hair follicles.
What is a dermatome?
Is the area of skin innervated by a single spinal nerve.
Dermatome maps, like the one on the next page, show us the cutaneous territories of each spinal nerve.
For example, sensation over the thumb is served by the C6 spinal nerve.
When examining sensation, we assess the patient’s ability to sense touch, pain, temperature, vibration, and joint position sense (proprioception)…
…because these different sensory modalities travel up the spinal cord via different pathways.
What is a Myotome?
the group of muscles innervated a single spinal nerve.
In clinical practice, we assess the myotomes by asking the patient to move the joint associated with that muscle group and nerve.
Where is the thoracic cavity?
The thoracic cavity is continuous with the neck via the superior thoracic aperture but is separated from the abdominal cavity by the diaphragm – a sheet of skeletal muscle that is vital for breathing.
Why does the diaphragm have openings?
Openings in the diaphragm allow structures to pass between the thorax and abdomen
What are the major organs in the thorax?
Heart and lungs
What does the thorax also contain?
● the trachea (windpipe), which passes from the neck to the thorax
● the oesophagus, which carries swallowed food and fluid to the stomach; it passes from the neck, into the thorax and through the diaphragm
● arteries and veins
● nerves – somatic and autonomic
● lymphatic vessels.
What is the thoracic cage (rib cage)?
is the bony skeleton of the thorax. It is semi-rigid and moves with breathing to allow the lungs to expand
What is the function of the thoracic cage?
● protects the thoracic (and some abdominal) viscera
● provides an attachment for the muscles of breathing and muscles that move the upper limb
● is composed of the sternum (breastbone), 12 pairs of ribs and the thoracic vertebrae.
Where is the sternum?
Lines anteriorly in the midline of the thoracic cage
What 3 parts is the sternum composed of?
● manubrium – the superior part
● body – inferior to the manubrium
● xiphoid process (or xiphisternum) – inferior to the body.
The suprasternal (jugular) notch.
The superior border of the manubrium has a notch in it
Laterally, the manubrium articulates with the clavicle (collarbone) at the sternoclavicular joint.
The manubrium and body of the sternum articulate with each other at the manubriosternal joint, also known as the sternal angle (or the ‘angle of Louis’).
How many pairs of ribs form the anterior, lateral and posterios walls of the thoracic cage?
12
What is the ribs made out of?
● The anterior parts of the ribs are composed of costal cartilage (costal = relating to the ribs). This gives the thoracic cage some ‘springiness’
● The ribs articulate with their costal cartilages at costochondral joints
● The costal cartilages of the upper ribs articulate with the sternum at sternocostal joints
● The ribs articulate posteriorly with the thoracic vertebrae at costovertebral joints
● Intercostal muscles lie in the intercostal spaces between the ribs and move the thorax for breathing
Thoracic vertebrae
Twelve thoracic vertebrae lie posteriorly in the midline of the thoracic cage.
They articulate with each other at intervertebral joints and with the posterior parts of the ribs at costovertebral joints.
What is the heart?
The heart is a sophisticated muscular pump.
It is composed of specialised smooth muscle and contracts constantly to keep blood moving through the lungs and body.
Specialised nerve cells and fibres in the heart
specialised nerve cells and fibres, which spontaneously generate and conduct the electrical activity that stimulates contraction of the myocardium (heart muscle).
These specialised nerve cells are under autonomic control – sympathetic stimulation increases the heart rate and parasympathetic stimulation decreases the heart rate.
4 chambers of the heart:
the right and left atria (singular = atrium) and the right and left ventricles.
The anatomy of the atria and ventricles is different (they look different) because they function differently.
Features and function of the ventricles:
The ventricles are the pumping chambers.
Their contraction generates high pressures to propel blood out of them, so their muscular walls are thicker than the atrial walls.
What is the function of valves within the heart?
ensure that blood flows only in one direction through the heart and cannot flow backwards
Where is the atrioventricular valves?
lie between the atria and ventricles (the tricuspid valve on the right and the mitral valve on the left)
What is the semilunar valve located?
Semilunar valves lie between the ventricles and the large blood vessels that carry blood from them (the pulmonary valve at the entrance to the pulmonary trunk and the aortic valve at the entrance to the aorta).
Which type of arteries supply the myocardium?
coronary arteries
The cardiopulmonary circulation
This is the circulation between the heart and lungs.
In the cardiopulmonary circulation, arteries carry deoxygenated blood and veins carry oxygenated blood (the opposite is true for the systemic circulation that serves the rest of the body)
Flow of blood in The cardiopulmonary circulation
● The right atrium receives deoxygenated blood from the body via large veins (the superior vena cava and inferior vena cava)
● From the right atrium, blood flows into the right ventricle
● The right ventricle pumps deoxygenated blood to the lungs via the pulmonary arteries
● Gas exchange occurs in the lungs
● Oxygenated blood from the lungs returns to the left atrium via the pulmonary veins
● From the left atrium, blood flows into the left ventricle
● The left ventricle pumps oxygenated blood to the body via the aorta.
What is true for both the systemic and cardiopulmonary circulations?
Veins carry blood towards the heart and arteries carry blood away from it
Structure and fucntions of the lungs
The lungs are spongy organs within which gas exchange takes place.
Each lung contains millions of microscopic air sacs called alveoli (singular = alveolus). Each adult lung contains approximately 300 million alveoli, depending on size.
Lobes of the lungs
Each lung is divided into lobes:
● The right lung has three lobes – a superior (upper), middle and inferior (lower) lobe
● The left lung has two lobes - an upper and a lower lobe
● Fissures separate the lobes.
Each lung is severed by:
● One pulmonary artery (carrying deoxygenated blood into the lung from the right ventricle)
● Two pulmonary veins (carrying oxygenated blood from the lung into the left atrium)
● One main bronchus (carrying air between the lung and the trachea)
To remember where the artery is in each lung
R ight
A anterior (to the bronchus)
L eft
S uperior (to the bronchus)
What is the bronchial tree?
describes the branching system of tubes that conduct air into and out of the lungs.
Structure of the bronchial tree
The trachea bifurcates into the left and right main bronchi, which enter the left and right lungs, respectively.
Each main bronchus divides into a series of smaller bronchi, which in turn divide into smaller tubes called bronchioles.
With each division, the bronchioles become smaller and smaller – the very smallest conduct air to and from the alveoli - the site of gas exchange within the lung
Role of muscle and cartilage in the bronchial tree
The walls of the trachea and bronchi contain smooth muscle and cartilage.
Cartilage acts as a scaffold and ensures that the trachea and bronchi remain open.
The walls of the bronchioles (smaller diameter conducting tubes) do not contain cartilage, only smooth muscle. The smooth muscle can contract or relax; this is under autonomic control
bronchoconstriction
● Parasympathetic stimulation narrows the bronchioles
bronchodilation.
● Sympathetic stimulation opens the bronchioles
What is surface anatomy?
Surface anatomy describes the study of anatomical structures by looking, feeling, and listening.
Involved: looking, feeling, listening
Looking
observing the patient is important. Some anatomical structures such as bones or parts of bones are usually clearly visible under the skin e.g. the clavicle.
We can use these visible landmarks to guide examination and procedures. We also look for any abnormal surface features or contours e.g. lumps or swellings.
Feeling
clinically, the term palpate is used (e.g. ‘the doctor palpated the patient’s pulse’).
Many anatomical structures are palpable, such as bones or parts of bones, blood vessels, muscles, and some organs.
Again, when examining a patient, we might palpate something that seems abnormal, like a lump or a swelling, or palpation might cause the patient pain.
Listening
clinically, the term auscultation is used (e.g. ‘the doctor auscultated the patient’s lungs’).
A stethoscope is used to auscultate the heart, lungs, and intestine. When we listen, we may hear sounds that are normal, or sounds that are abnormal in some way.
Why is the sternal angle a key surface landmark?
because it lies at the same level as the second ribs - and from here we can count the rest of the ribs.
What are 2 co-ordinates used for?
to visualise deep structures or to describe locations in the chest
North-south coordinate
provided by the ribs
East-west coordinate (midline-lateral coordinate)
use imaginary vertical lines drawn down the thorax, to describe a location relative to the midline
Midsternal (anterior median) line
drawn straight down the centre of the sternum
Midclavicular line
drawn inferiorly from the midpoint of the clavicle.
Anterior axillary line
Drawn inferiorly from the anterior axilla (armpit).
Midaxillary line
drawn inferiorly from the middle of the axilla.
Posterior axillary line
drawn inferiorly from the posterior axilla
Scapula line
drawn inferiorly through the scapula.
Midvertebral (posterior median) line
drawn straight down along the spinous
processes of the vertebrae
