Functional Anatomy of the Lumbar Spine and Abdominal Wall: Difference between revisions
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The lumbar spine is considered a three-joint complex or the articular triad.<ref name=":2" /> The zygapophyseal joint or facet joints and intervertebral disk joints belong to the spinal motion segment, which, when worked together, allow spinal motion and protect the spine from excessive movements. | The lumbar spine is considered a three-joint complex or the articular triad.<ref name=":2" /> The zygapophyseal joint or facet joints and intervertebral disk joints belong to the spinal motion segment, which, when worked together, allow spinal motion and protect the spine from excessive movements. | ||
Revision as of 11:44, 26 June 2023
Top Contributors - Ewa Jaraczewska, Jess Bell, Robin Tacchetti, Kim Jackson and Lucinda hampton
Introduction[edit | edit source]
The lower back typically includes five vertebrae in the lumbar region and supports much of the upper body's weight. Intervertebral discs maintain the spaces between the vertebrae, which act like shock absorbers throughout the spinal column to cushion the bones as the body moves. Ligaments hold the vertebrae in place, and tendons attach the muscles to the spinal column. The skeletal support of the abdominal wall includes the vertebral column and lower ribs. It contains the skin, fascia, and muscle, which provide coverage for the organs, generates inter-abdominal pressure, and move the vertebral column. This article discusses the key anatomical structures of the lumbar vertebra and abdominal wall, including the bony structures, articulations, ligaments, muscles, nerves and the vascular supply.
Key Terms[edit | edit source]
Axes: lines around which an object rotates. The rotation axis is a line that passes through the centre of mass. There are three axes of rotation: sagittal passing from posterior to anterior, frontal passing from left to right, and vertical passing from inferior to superior. The rotation axes of the foot joints are perpendicular to the cardinal planes. Therefore, motion at these joints results in rotations within three planes. Example: supination involves inversion, internal rotation, and plantarflexion.
Bursae: reduce friction between the moving parts of the body joints. A bursa is a fluid-filled sac. There are four types of bursae: adventitious, subcutaneous, synovial, and sub-muscular.
Capsule: one of the characteristics of the synovial joints. It is a fibrous connective tissue which forms a band that seals the joint space, provides passive and active stability and may even form articular surfaces for the joint. The capsular pattern is "the proportional motion restriction in range of motion during passive exercises due to tightness of the joint capsule."
Closed pack position: the position with the most congruency of the joint surfaces. In this position, joint stability increases. For example, the closed pack position for the interphalangeal joints is a full extension.
Degrees of freedom: the direction of joint movement or rotation; there is a maximum of six degrees of freedom, including three translations and three rotations.
Ligament: fibrous connective tissue that holds the bones together.
Open (loose) pack position: position with the least joint congruency where joint stability is reduced.
Planes of movement: describe how the body moves. Up and down movements (flexion/extension) occur in the sagittal plane. Sideway movements (abduction/adduction) occur in the frontal plane. The transverse plane movements are rotational (internal and external rotation).
Lumbar Spine Structure[edit | edit source]
Lumbar vertebrae[edit | edit source]
L1-L5 are known as lumbar vertebrae. However, 10–17.4% of adults present with a spinal abnormality of having the 6th lumbar vertebra.[1] This abnormality may influence the saggital parameters, including a diminished sacral tilt and more vertical sacrum. [2] The presence of additional lumbar vertebrae can be associated with a decrease in the number of thoracic vertebrae (individuals with eleven thoracic vertebrae).
The lumbar vertebrae are located between the 12th thoracic vertebra and the sacrum bone. They are the largest vertebrae of the human body. Each lumbar vertebra contains the following structural elements:
- Vertebral body
- Kidney-shaped
- Wider from side to side than from front to back
- The posterior aspect of the vertebral body changes from concave to convex
- Vertebral foramen
- Triangular in shape
- Larger than in the thoracic vertebrae but smaller than in the cervical vertebrae
- Two pedicles
- Posterior element of the lumbar vertebra
- Attach to the cranial half of the vertebral body
- Becoming shorter, broader and more lateral from L1 - L5
- Two laminae
- Flat and broad
- Two pedicles and two laminae form the vertebral arch
- Centrally connects to a spinous process
- Spinous process
- Projects perpendicularly from the body
- Short and sturdy
- Describe as a "hatchet-shaped"
- Point of muscle and ligament attachment
- Two transverse processes
- Located on the posterior surface
- Project laterally on each side of the vertebra
- Long and slender
- Points of muscle and ligaments attachment
- L1-L3 projecting horizontally
- L4-L5 projecting upward
- Four articular processes[3]
- Two superior articular facets and two inferior articular facets
- The point where two facets are joining is called the zygapophyseal joints
Lumbar Lordosis[edit | edit source]
The natural curve for the lumbar spine is lordosis. It defines lumbar spine alignment in the saggital plane. However, the pelvis is "the cornerstone of spinal sagittal alignment". [4] The curve of the sacrum determines the lumbar curve.
The lumbar spine sagittal alignment offers two main benefits during locomotion: [4]
- Allows the body's centre of mass to be positioned above the hip, knee, and ankle joints
- Minimises the muscular force used for postural control
Assessment of the lumbar spine alignment must include the analysis of the lower limbs alignment. The knee flexion angle measurement and pelvic shift results can help identify the compensatory mechanisms resulting from the sagittal plane malalignment. [5]
Abdominal Wall Structure[edit | edit source]
The abdominal wall has skeletal support made of the vertebral column and lower ribs posteriorly and connects to the thoracic cage at the superior end and pelvic bones inferiorly. It is defined by the following landmarks: xiphoid process and costal cartilages of the 7th–10th ribs outline the superior border, the umbilicus in the middle, and inguinal ligament, pubic crest and pubic symphysis define the inferior border.
You can read more about pelvis anatomy here.
Bones, Articulations and Kinematics of the Lumbar Spine[edit | edit source]
Bones and Articulations[edit | edit source]
The lumbar spine has two types of joints located between each lumbar vertebra: the intervertebral disc joint and the zygapophyseal joint or the facet joint. The intervertebral disc joint is formed between the vertebral bodies and is separated by the intervertebral disc. The zygapophyseal joints are formed between the articular processes of each lumbar vertebra.
Bones | Articulations | Characteristics | Key palpation points |
---|---|---|---|
Vertebral body | Intervertebral disc joint | This joint is formed between the inferior surface of one vertebral body and the superior surface of the vertebral body that lies below (for example, the inferior surface of L1 and the superior surface of L2). An intervertebral disc separates the vertebral bodies. | To find each segment of the lumbar spine, position the patient prone. The location of the spinal processes will determine the location of each segment. You can palpate the spinal processes in the centre of the patient's back.
Start with finding T12 by palpating the patient's lowest rib and following your finger along the border of the rib towards the centre of the spine.T12 spinal process is in line with the 12th rib that inserts into the spinal segment. Below T12, you can palpate L1 and continue along the spinal process of L2, L3, and L4. When starting your palpation from the distal end of the lumbar spine, you must consider the following caution: the spinal process of L4 "is usually determined by the position of the highest point on both sides of PSIS"[6], and the accuracy of palpation is only 36%.[6] |
Articular processes | Zygapophyseal joint (Facet joint) | Located on the left and right sides of the spine
Links one vertical segment to the other. For example, a facet joint between L3 and L4 will connect L3 to L4. The superior articular surface is vertical and concave, and the inferior is vertically convex. The primary role includes the stabilization of the spinal motion segment.[7]C Contribute to axial compressive load transmission on the spine |
The facet joint CANNOT be directly palpated due to overlying soft tissue. When you move your fingers two to three centimetres in the lateral direction from the spinal process, you will be on the muscles overlying the facet joint. |
Kinematics[edit | edit source]
The lumbar spine is considered a three-joint complex or the articular triad.[7] The zygapophyseal joint or facet joints and intervertebral disk joints belong to the spinal motion segment, which, when worked together, allow spinal motion and protect the spine from excessive movements.
The following is the characteristic of the spinal motion segment:[8]
- The intervertebral disk joints transmit mostly vertical compressive loads
- The facet joints guide and stabilise the motion segment
- In the erect standing position and erect sitting posture, spine load is also transmitted through the facet joints
Joint | Type of joint | Plane of movement | Motion | Kinematics | Closed pack position | Open pack position |
---|---|---|---|---|---|---|
Intervertebral disc joint | Cartilaginous joint, symphysis | A single joint: structurally fused but allows very limited, multidirectional movements
All lumbar intervertebral disc joints and zygapophyseal joints combined together: Saggital Frontal Transverse |
Single joint: Translating, tilting, rocking and compressing movements
All lumbar intervertebral disc joints and zygapophyseal joints combined together: Flexion/Extension Lateral flexion Rotation |
All lumbar intervertebral disc joints and zygapophyseal joints combined together:
Flexion 60 degrees Extension 25 degrees Lateral flexion 20-30 degrees Rotation 1-5 degrees |
Full extension | Halfway between flexion and extension |
Zygapophyseal joint (facet joint) | Synovial plane joint | Facilitate a multiplanar and multidirectional movement of the spine
Enable lumbar spine extension, lateral flexion, and rotation in the saggital transverse and frontal planes. |
Flexion/Extension
Lateral flexion Rotation |
All lumbar intervertebral disc joints and zygapophyseal joints combined together:
Flexion:60 degrees Extension 25 degrees Lateral flexion 20-30 degrees Rotation 1-5 degrees |
Full extension | Halfway between flexion and extension |
Lumbar Spine Ligaments[edit | edit source]
Key ligaments | Origin | Insertion | Action/role | Key palpation points |
---|---|---|---|---|
Anterior longitudinal ligament | The anterior portion of the vertebral body at the base of the skull | The anterior portion of the vertebral body at the sacrum | Limits extension of the vertebral column
Reinforces the intervertebral disc |
|
Posterior longitudinal ligament | The body of the C2 | Posterior surface of the sacrum | Limits flexion of the vertebral column
Reinforces the intervertebral disc |
|
Ligamentum flavum:
Series of short ligaments that connects the laminae of each vertebra.[9] There are two ligamenta flava at each vertebra. Each ligament is divided into: The medial portion: passes to the back of the next lower lamina and across the gap between the adjacent vertebrae fusing with the interspinous ligament The lateral portion: passes in front of the facet joint, attaches to the anterior aspect of the inferior and superior articular processes and forms the anterior capsule. Most lateral fibres extend beyond the superior articular process to the pedicle below. |
The lower half of the anterior surface of the lamina above | The posterior surface and upper margin of the lamina below | High elastin content, which prevents the ligament from buckling into the spinal canal. [9]
Assists with lumbar spine flexion and extension. Compresses the intervertebral discs. |
|
Intertransverse ligaments | Transverse processes of the vertebra above | Transverse processes of the vertebra below | Contributes to the stability of the lumbar spine
Provides the opposite side resistance during lateral flexion |
To palpate the transverse process, the patient is sitting. The transverse processes of the lumbar spine are most likely located directly in line with the spinous process of the corresponding vertebra. Start with palpating the spinous process of the L1 vertebra and move directly lateral to find the spinal process of L1. |
Supraspinous ligament | Tip of spinous processes of the vertebra above from the seventh cervical vertebra to the third or fourth lumbar vertebra | Tip of spinous processes of the vertebra below | Prevents the separation of the spinous processes during forward flexion, thus limiting lumbar spine flexion | You can palpate the spinous processes in the centre of the patient's back.
Start with finding T12 by palpating the patient's lowest rib and following your finger along the border of the rib towards the centre of the spine.T12 spinous process is in line with the 12th rib that inserts into the spinal segment. Below T12, you can palpate L1 and continue along the spinous process of L2, L3, and L4. |
Interspinous ligament | Spinous processes of the vertebra above between the ligamenta flava anteriorly and the supraspinous ligament posteriorly | Spinous processes of the vertebra below between the ligamenta flava anteriorly and the supraspinous ligament posteriorly | Limits forward flexion of the vertebral column. |
Muscles of the Lumbar Spine and Abdominal Wall[edit | edit source]
The muscles of the back can be grouped according to their function and according to their location.
Based on the function the muscles of the lumbar spine are the following:
- Flexors: psoas major, psoas minor, internal oblique, external oblique, and rectus abdominis
- Extensors: quadratus lumborum, interspinales lumborum, multifidus, and the erector spinae (iliocostalis, longissimus)
- Lateral flexors: intertransversarii lumborum, psoas major, quadratus lumborum, erector spinae, internal and external obliques
- Rotators: multifidus, internal and external obliques
According to the location, the muscles of the lumbar spine can be divided as follow:
- The intrinsic (deep) group
- Superficial layer: erector spinae muscles
- Middle (deep) layer: multifidus
- Deepest layer: interspinales lumborum and intertransversarii lumborum
- The abdominal wall group: transverse abdominis, the internal oblique, rectus abdominis, and the external oblique
- The hip group: psoas major, psoas minor, quadratus lumborum
Lumbar Spine Flexors[edit | edit source]
Muscle | Origin | Insertion | Innervation | Action |
---|---|---|---|---|
Psoas major | Vertebral bodies of T12-L4, intervertebral discs between T12-L4, transverse processes of L1-L5 vertebrae | Lesser trochanter of femur | Anterior rami of spinal nerves L1-L3 | Bilateral action and when the insertion point is fixed: contribute to lumbar spine flexion.[9] |
Psoas minor | Vertebral bodies of T12 to L1 | Iliopubic eminence | Anterior ramus of spinal nerve L1 | Weak trunk flexor. It can be absent in 40% of people. [9] |
Internal obliques | Thoracolumbar fascia
Iliac crest Inguinal ligament |
Lower four ribs
Linea alba Pubic crest |
Lower intercostal nerves Branches of the lumbar plexus: iliohypogastric nerve and ilioinguinal nerve. | Bilateral action: lumbar flexion
Assists in raising intra-abdominal pressure |
External obliques | Ribs five to twelve | Linea alba Pubic tubercle
Iliac crest |
Intercostal nerves T7- T11 and the T12 subcostal nerve | Bilateral action: lumbar flexion |
Rectus abdominis | Pubis
Pubic symphysis |
Xiphoid process of the sternum
The fifth to the seventh costal cartilage |
Thoracoabdominal nerves | Lumbar spine flexion
Assists in raising intra-abdominal pressure |
Lumbar Spine Extensors[edit | edit source]
Muscle | Origin | Insertion | Innervation | Action |
---|---|---|---|---|
Quadratus lumborum | Iliac crest
Iliolumbar ligament |
The inferior border of the 12th rib
Transverse processes of L1-L4 vertebrae |
Subcostal nerve
Anterior rami of spinal nerves L1-L4 |
Bilateral action: trunk extension |
Interspinales lumborum | Superior aspects of spinous processes of L2-L5 | Inferior aspects of spinous processes of L1-L4 | Posterior rami of spinal nerves | Stabilise the lumbar spine. Extend the lumbar spine. |
Multifidus | Sacrum
Posterior superior iliac spine The mammillary processes of the lumbar vertebrae Transverse processes of T1-3 Articular processes of C4-C7 |
Spinous processes of the vertebrae above their origin | Medial branches of posterior rami of spinal nerves in the corresponding lumbar region | Extends the lumbar spine
Provides core stability |
Erector spinae: Iliocostalis lumborum (ICL) Longissimus thoracis (LT) | ICL: Iliac crest
LT : Lumbar intermuscular aponeurosis, medial part of sacropelvic surface of ilium, posterior sacroiliac ligament |
ICL: L1-L4 lumbar transverse processes, angle of 4-12 ribs and thoracolumbar fascia
LT: Accessory and transverse processes of vertebrae L1-L5 |
Dorsal rami of spinal nerves | Bilateral action: lumbar spine extension |
Lumbar Spine Lateral Flexors[edit | edit source]
Muscle | Origin | Insertion | Innervation | Action |
---|---|---|---|---|
Intertransversarii lumborum (ITL):
Lateral (ITLL) Medial (ITLM) |
ITLL: Transverse and accessory processes of L1-L4
ITLM: Accessory processes of L1-L4 |
ITLL: Transverse process of the following vertebra
ITLM: Mammillary processes of the following vertebra |
Anterior rami of spinal nerves | Assists in lateral flexion
Stabilises the lumbar spine |
Psoas major | Vertebral bodies of T12-L4, intervertebral discs between T12-L4, transverse processes of L1-L5 vertebrae | Lesser trochanter of femur | Anterior rami of spinal nerves L1-L3 | Lateral flexion of the trunk |
Quadratus lumborum | Iliac crest
Iliolumbar ligament |
The inferior border of the 12th rib
Transverse processes of L1-L4 vertebrae |
Subcostal nerve
Anterior rami of spinal nerves L1-L4 |
Unilateral action: ipsilateral lumbar spine lateral flexion |
Erector spinae:
Iliocostalis (IC) Longissimus (L) |
ICL: Iliac crest
LT : Lumbar intermuscular aponeurosis, medial part of sacropelvic surface of ilium, posterior sacroiliac ligament |
ICL: L1-L4 lumbar transverse processes, angle of 4-12 ribs and thoracolumbar fascia
LT: Accessory and transverse processes of vertebrae L1-L5 |
Dorsal rami of spinal nerves | Unilateral action: ipsilateral side flexion and rotation of the vertebral column |
Internal oblique | Thoracolumbar fascia
Iliac crest Inguinal ligament |
Lower four ribs
Linea alba Pubic crest |
Lower intercostal nerves
Branches of the lumbar plexus: iliohypogastric nerve and ilioinguinal nerve. |
Unilateral action: lumbar spine lateral flexion and/or rotation to the ipsilateral side
Assists in raising intra-abdominal pressure |
External oblique | Ribs five to twelve | Linea alba Pubic tubercle
Iliac crest |
Intercostal nerves T7- T11 and the T12 subcostal nerve | Unilateral action: lumbar spine lateral flexion to the ipsilateral side and rotation to the contralateral side |
Lumbar Spine Rotators[edit | edit source]
Muscle | Origin | Insertion | Innervation | Action |
---|---|---|---|---|
Multifidus | Sacrum
Posterior superior iliac spine The mammillary processes of the lumbar vertebrae |
Spinous processes of the vertebrae above their origin | Medial branches of posterior rami of spinal nerves in the corresponding lumbar region. | Rotates the lumbar spine away from the side of the body on which they are located
Provides core stability |
Internal oblique (IO) | Thoracolumbar fascia
Iliac crest Inguinal ligament |
Lower four ribs
Linea alba Pubic crest |
Lower intercostal nerves
Branches of the lumbar plexus: iliohypogastric nerve and ilioinguinal nerve. |
Rotation to the same side
Work together with EO: right external and left internal oblique rotate the spine. |
External oblique (EO) | Ribs five to twelve | Linea alba Pubic tubercle
Iliac crest |
Intercostal nerves T7- T11 and the T12 subcostal nerve | Rotation to the opposite side
Work together with IO: right external and left internal oblique rotate the spine. |
Innervation of the Lumbar Spine and Abdominal Wall[edit | edit source]
Nerve | Origin | Branches | Motor fibres | Sensory fibres |
---|---|---|---|---|
Intercostal | Lumbar plexus | Muscular, collateral, lateral cutaneous, anterior cutaneous, and
communicating branches |
External obliques
Internal obliques |
Skin over the anterior abdomen |
Subcostal | Anterior ramus of the spinal nerve T12 | Muscular, cutaneous, communicating and collateral branches | Quadratus lumborum
External oblique |
The skin of the region under the umbilicus |
Iliohypogastric | Lumbar plexus | Lateral cutaneous branch
Anterior cutaneous branch |
Internal oblique | External abdominal oblique, transversus abdominis, internal abdominal oblique
The skin of the suprapubic region |
Ilioinguinal | Lumbar plexus | Anterior labial nerves
Anterior scrotal nerves |
Internal oblique | |
Dorsal (posterior) rami of spinal nerves | Spinal nerves | Medial
Intermediate Lateral |
Interspinales lumborum
Multifidus Erector spinae |
The skin of the back |
Ventral (anterior) rami of L1-L4 | Spinal nerves | Intertransversarii lumborum
Psoas major Psoas minor |
Ventrolateral body surface Structures in the body wall |
Vascular Supply of the Lumbar Spine and Abdominal Wall[edit | edit source]
Artery | Origin | Branches | Supply |
---|---|---|---|
Lumbar artery (LA):
Left (LLA) Right (RLA) |
Abdominal aorta | Medial
Middle Lateral |
Skin and muscles of the posterior abdominal wall
Joints of the lumbar spine The lumbar portion of the deep back muscles Lower two-thirds of the spinal cord |
Internal thoracic artery | Subclavian artery | Anterior collaterals
Posterior collaterals Terminal branches |
The superior aspect of the abdominal wall |
External iliac artery | Common iliac artery | Inferior epigastric,
Deep circumflex iliac arteries |
Lower abdominal wall |
Clinical Relevance[edit | edit source]
- Disc herniations are common low back conditions. They are defined by the nucleus pulposus displacing from intervertebral space. According to Yoon et al., imaging confirmation of lumbar disc herniation, "consistent with clinical findings, and failure to improve after six weeks of conservative care", may require surgical intervention.[10] You can read more about disc herniations symptoms management here.
- Spinal stenosis is a narrowing of the spinal canal. Spinal stenosis can also result from other factors, such as tumours or bone spurs. You can learn about low back pain assessment and prognosis by taking this course.
- Diastasis recti is an extremely frequent condition[11] where the linea alba stretches and produces a gap between the two sides of the rectus abdominis muscle.[9] Learn more about diastasis recti here.
Resources[edit | edit source]
- Inoue N, Orías AAE, Segami K. Biomechanics of the Lumbar Facet Joint. Spine Surg Relat Res. 2019 Apr 26;4(1):1-7.
- Kostov S, Dineva S, Kornovski Y, Slavchev S, Ivanova Y, Yordanov A. Vascular Anatomy and Variations of the Anterior Abdominal Wall - Significance in Abdominal Surgery. Prague Med Rep. 2023;124(2):108-142.
- Clinical Physio. Lumbar Spine Palpation
References[edit | edit source]
- ↑ Yan YZ, Li QP, Wu CC, Pan XX, Shao ZX, Chen SQ, Wang K, Chen XB, Wang XY. Rate of the presence of 11 thoracic vertebrae and 6 lumbar vertebrae in asymptomatic Chinese adult volunteers. J Orthop Surg Res. 2018 May 23;13(1):124.
- ↑ Yan YZ, Wang B, Huang XQ, Ru X, Wang XY, Qu HB. Variation in Global Spinal Sagittal Parameters in Asymptomatic Adults with 11 Thoracic Vertebrae, four Lumbar Vertebrae, and six Lumbar Vertebrae. Orthop Surg. 2022 Feb;14(2):341-348.
- ↑ Waxenbaum JA, Reddy V, Williams C, Futterman B. Anatomy, Back, Lumbar Vertebrae. 2022 Aug 1. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan–.
- ↑ 4.0 4.1 Diebo BG, Varghese JJ, Lafage R, Schwab FJ, Lafage V. Sagittal alignment of the spine: What do you need to know? Clin Neurol Neurosurg. 2015 Dec;139:295-301.
- ↑ Schwab F, Lafage V, Boyce R, Skalli W, Farcy JP. Gravity line analysis in adult volunteers: age-related correlation with spinal parameters, pelvic parameters, and foot position. Spine (Phila Pa 1976). 2006 Dec 1;31(25):E959-67.
- ↑ 6.0 6.1 Feng Q, Zhang L, Zhang M, Wen Y, Zhang P, Wang Y, Zeng Y, Wang J. Morphological parameters of fourth lumbar spinous process palpation: three-dimensional reconstruction of computed tomography. J Orthop Surg Res. 2020 Jun 22;15(1):227.
- ↑ 7.0 7.1 Kapetanakis S, Gkantsinikoudis N. Anatomy of lumbar facet joint: a comprehensive review. Folia Morphol (Warsz). 2021;80(4):799-805.
- ↑ Inoue N, Orías AAE, Segami K. Biomechanics of the Lumbar Facet Joint. Spine Surg Relat Res. 2019 Apr 26;4(1):1-7.
- ↑ 9.0 9.1 9.2 9.3 9.4 Xuan D. Exploring Lumbar Spine and Abdominal Wall Anatomy. Plus 2023
- ↑ Yoon WW, Koch J. Herniated discs: when is surgery necessary? EFORT Open Rev. 2021 Jun 28;6(6):526-530.
- ↑ Cavalli M, Aiolfi A, Bruni PG, Manfredini L, Lombardo F, Bonfanti MT, Bona D, Campanelli G. Prevalence and risk factors for diastasis recti abdominis: a review and proposal of a new anatomical variation. Hernia. 2021 Aug;25(4):883-890.
- ↑ Clinical Physio. Lumbar Spine Palpation. Available from: https://www.youtube.com/watch?v=XrQP3AeDjiM [last accessed 25/6/2023]