Lab 1/2 Prep: Questions for Dissection 1-2 (CARDIO)
Question 1: Specimen: Equine skeleton (Page 68)
Thorax vs Thoracic cavity
Thorax: skeletal framework of the chest containing ribs, sternum, thoracic vertebrae, and associated structures.
Thoracic cavity: the space within the thorax that houses the lungs, heart, and other organs.
Thoracic inlet vs Thoracic outlet
Thoracic inlet: the opening at the cranial thorax where the thorax communicates with the neck; bounded by the first thoracic vertebra, first pair of ribs, and manubrium.
Thoracic outlet: the caudal boundary of the thoracic cavity where structures exit into the abdomen/pelvis; bounded by the first lumbar vertebra and the thoracic-diaphragmatic junction (conceptual, in practice defined by diaphragm and rib cage limits).
Skeleton divided into axial and appendicular parts
Axial skeleton: skull (cranial bones), auditory ossicles, hyoid apparatus, vertebral column, sternum, ribs.
Appendicular skeleton: bones of the limbs and their girdles (pectoral girdle, pelvic girdle).
Six major functions of the skeleton
Support for the body
Protection of vital organs (e.g., brain, spinal cord, heart, lungs)
Movement facilitation (levers for muscles)
Mineral storage (calcium, phosphorus)
Blood cell production (bone marrow in many bones)
Endocrine/regulatory roles (osteokines, marrow activity)
Front (thoracic) limb attachment to the axial skeleton
Attached via the pectoral girdle (scapula, clavicle in some species) to the axial skeleton through the sternum and rib cage, and at the shoulder girdle to the thoracic wall and spine regions.
Hind (pelvic) limb attachment to the axial skeleton
Attached via the pelvic girdle (ilium, ischium, pubis) to the sacrum (via sacroiliac joints) and vertebral column, creating a rigid posterior anchorage.
Reasons for differing attachments to the axial skeleton
Differences in weight-bearing, locomotor mechanics, and load transfer: forelimbs primarily support weight and absorb shock through shoulder girdle; hind limbs provide propulsion and transfer weight through the pelvis to the spine.
Visualizing synovial, fibrocartilage, and fibrous joints on this skeleton
Synovial joints: highly movable joints (e.g., shoulder, elbow, hip, knee) with a synovial cavity, articular cartilage, joint capsule, ligaments, and synovial fluid.
Fibrocartilage joints: joints with fibrocartilaginous interpositions (e.g., intervertebral discs, pubic symphysis).
Fibrous joints: bones joined by fibrous connective tissue with minimal or no movement (e.g., cranial sutures, distal tibiofibular joint in some species).
Question 2: Specimen: Canine skeleton (Page 69)
Approximate total bones in a canine skeleton
About 200 bones (roughly on the order of two hundred; exact counts vary with breed/individual).
Meaning of “visceral skeleton”
Bones that develop within soft tissues of the visceral region; exemplified by the penile bone and analogous structures in other species.
Visceral skeleton bone in the male dog
Os penis (penile bone).
Visceral skeleton element in the female dog?
Os clitoridis (clitoral bone) may be present in some species; in the female dog this element is the analogue to the male os penis (visceral skeleton), but its presence is variable.
The five “types of bones” making up the skeleton with an example, location, and function
Long bones: e.g., femur; function as levers and supports limb length.
Short bones: e.g., carpal bones; function as weight-bearing and confined movement.
Flat bones: e.g., scapula, sternum; function in protection and broad attachment surfaces.
Irregular bones: e.g., vertebrae; function in protection and complex shapes.
Sesamoid bones: e.g., patella; function to modify pressure, alter muscle pull, and protect tendons.
Vertebral regions and counts in the dog
Cervical region vertebrae: 7 (C7).
Thoracic region vertebrae: 13 (T13).
Lumbar region vertebrae: 7 (L7).
Sacral region vertebrae: 3 (fused to form the sacrum).
Caudal (coccygeal) vertebrae: 20–25 (Cd_{20-25}).
Verification of vertebral counts in domestic animals
In domestic animals, the cervical count is 7, and the thoracic count commonly equals the number of rib pairs (yes: 13 ribs correspond to 13 thoracic vertebrae in dogs).
How many vertebrae in the canine neck (cervical region)?
7 cervical vertebrae.
How many vertebrae in the canine thoracic region? and relation to ribs
13 thoracic vertebrae; number of thoracic vertebrae equals number of rib pairs (Yes).
How many vertebrae in the canine lumbar region?
7 lumbar vertebrae.
Sacral region fusion and its reasons
The three sacral vertebrae fuse to form a single sacrum.
How to tell fusion? A single fused bone with enlarged ventral surfaces and a consolidated sacral mass; reflects embryologic fusion and functional rigidity.
Why fusion occurs: provides a rigid, strong base for transferring weight from the spine to the pelvis and hind limbs.
Immobility of the sacral region and its purpose
The sacrum is immovable to stabilize the pelvis and transfer load to the pelvic girdle.
Number of caudal vertebrae in most dogs
About 20 caudal vertebrae (tail length varies).
Vertebral formula definitions and dog/horse formulas
Vertebral formula = counts in each region of the vertebral column. Example provided below.
Dog:
Horse:
Three major functions of the vertebral column
Protects the spinal cord.
Provides structural support and framework for the body.
Allows movement and flexibility via intervertebral joints and ligaments.
Costal arch: definition, pairing, significance
Costal arch is formed by the costal cartilages (ribs) on both sides; it is paired (right and left).
Practical significance: contributes to the boundary of the thoracic cavity; provides attachment surfaces for abdominal and thoracic muscles; influences chest contour.
Difference of the 11th thoracic vertebra (anticlinal vertebra) in the dog and its radiological significance
The 11th thoracic vertebra is termed the anticlinial vertebra; it typically has distinctive dorsal spines and marks a transition point in vertebral column orientation.
Radiological significance: serves as a landmark on radiographs for assessing spinal alignment and vertebral counting.
Question 3: Specimen: An Equine Vertebra (Page 71)
True/false statements about vertebrae
A vertebra is an irregular bone: True
A vertebra is located along the midline: True
A vertebra is unpaired: True (one per segment along the spine)
The dog exhibits about 50 vertebrae: False (dogs have more, but not ~50 total; the exact number varies by region)
Typical vertebra structures present in most vertebrae
Body, arch (vertebral foramen), processes, articular surfaces
These can be identified on a typical vertebra; front (cranial) and back (caudal) articular surfaces exist in pairs.
Task: Draw a labelled diagram of a typical vertebra
Recognize two cranial articular surfaces (left and right) and two caudal articular surfaces (left and right).
Direction of articular surfaces
In this specimen, the articular surfaces run horizontally (craniocaudal direction across the vertebra).
Function of vertebral column through different articular orientations
Horizontally directed articular surfaces enable lateral gliding and some degree of rotation.
Vertically directed articular surfaces enable flexion and extension (up-down bending).
Regional origin of the vertebra in the specimen
Identify the vertebral region from which this vertebra comes (cervical, thoracic, lumbar, etc.) by comparing features such as body size, processus, and articulation surfaces.
Question 4: Sequence of Four Equine Vertebrae (Last two thoracic vertebrae and first two lumbar vertebrae) (Page 72)
Define intervertebral foramen and list structures passing through it
Intervertebral foramen: opening formed between consecutive vertebrae through which spinal nerves and accompanying vessels exit the vertebral canal.
Regions where intervertebral discs are absent and why
The "Yes" joint (occipito-atlantal), the "No" joint (atlanto-axial), and near the hind (pelvic) limb (sacral region) where the vertebral column fuses to form the sacrum; discs are absent in these joints due to specialized articulations and stability requirements.
Is the vertebral column the same as the spine or the back
Yes; synonyms for the same structure.
Distinction between vertebral foramen and vertebral canal
Vertebral foramen: opening within a single vertebra; vertebral canal: the canal formed by the stacking of vertebral foramina along the spine.
Structures travelling through the vertebral canal
Spinal cord, meninges, and associated blood vessels; supported by the vertebral column.
Intercentral joints between bodies of adjacent typical vertebrae and relation to slipped disc
Intercentral joints are cartilaginous joints between adjacent vertebral bodies; they relate to the integrity of the intervertebral discs and the occurrence of a slipped (herniated) disc when the nucleus pulposus protrudes through the annulus fibrosus.
Joints between articular surfaces of adjacent typical vertebrae and how/where flexion and extension occur
Zygapophysial (facet) joints between articular processes; orientation of facets determines the degree and direction of flexion/extension.
Ligaments shown between two adjacent typical vertebrae (diagrammatic inclusion)
Anterior longitudinal ligament, posterior longitudinal ligament, dorsal/ventral ligaments, interspinous ligaments, supraspinous ligament, and nuchal ligament (in some species) provide stability.
Three atypical vertebrae and how they differ from a typical vertebra
Atlas (C1): lacks a vertebral body; supports skull; large vertebral foramen; no true spinous process.
Axis (C2): has the dens (odontoid process) that articulates with C1; provides pivotal movement; body present.
Anticlinal vertebra (e.g., T11 in the dog): exhibits distinctive spine and articular facet orientation, affecting spinal curvature and radiographic features.
Vertebral numbers for four equine vertebrae in the given specimen (last two thoracic and first two lumbar)
Horse has 18 ribs; thus the last two thoracic vertebrae are T17 and T18, and the first two lumbar vertebrae are L1 and L2.
Question 5: Specimens: A Canine and an Equine Cervical Vertebra (Page 73)
Major positive 2–3 features of a cervical vertebra
Presence of transverse foramina in typical cervical vertebrae (for vertebral artery and vein passage).
Smaller body relative to thoracic/lumbar vertebrae; presence of a hollowed vertebral foramen.
Bifid or notched transverse processes in many cervical vertebrae, and relatively short spinous processes (vary by species).
Negative features to contrast with cervical vertebrae
They lack features typical of thoracic or lumbar vertebrae, such as prominent articular surfaces oriented for rib articulation (costal facets) and longer spinous processes.
Function of transverse foramina
For the passage of the vertebral artery and vein; protection of vascular supply to the brain.
Structures passing through the transverse foramina
Vertebral arteries and veins (and accompanying sympathetic nerves in some species).
Question 6: Specimens: A Canine and an Equine Thoracic Vertebra (Page 74)
Major positive features of a thoracic vertebra
Presence of costal facets on the vertebral body for articulation with ribs.
Presence of a long downward-pointing spinous process and robust vertebral arch.
Negative features (not exhibited in thoracic vertebrae but present in other regions)
Absence of large transverse foramina for vertebral arteries (compared to cervical vertebrae); less pronounced body shapes than lumbar vertebrae; no accessory processes found in some regions.
How ribs affect the thoracic vertebra anatomy
Ribs articulate with thoracic vertebrae via costal facets on the body and with each other via costal cartilages; rib attachments shape the thoracic vertebrae and contribute to the rib cage architecture.
Identification of the 11th canine thoracic vertebra and how it differs
The 11th thoracic vertebra is the anticlinial vertebra with distinctive features (e.g., taller dorsal spine) compared with other thoracic vertebrae.
A sensible name for the 11th canine thoracic vertebra
The anticlinial vertebra (T11) in the canine thoracic series.
Question 7: Specimens: A Canine and an Equine Lumbral Vertebra (Page 75)
Main 2–3 anatomical features of a lumbar vertebra, including positive and negative features
Positive: large vertebral body to bear weight; absence of articulation with ribs; robust processes; relatively short transverse processes.
Negative: lacks rib facets; articular processes oriented to permit flexion/extension with less lateral rotation than thoracic vertebrae.
How many lumbar vertebrae does the dog exhibit?
7 lumbar vertebrae.
Question 8: Specimens: The Canine, Equine, Bovine and Porcine Sacra (Page 76)
Important anatomical features of the canine sacrum
Sacrum formed by fused sacral vertebrae (usually 3 in the dog).
Statements about sacral counts in different species
Canine sacrum: 3 fused sacral vertebrae.
Porcine sacrum: 4 fused sacral vertebrae.
Equine sacrum: 5 fused sacral vertebrae.
Bovine sacrum: 5 fused sacral vertebrae.
Human sacrum: 5 fused sacral vertebrae.
Relationship between the unpaired sacrum and hind limbs
The sacrum forms a critical link between the spine and the pelvic girdle; it articulates with the ilia via the sacroiliac joints to transmit load to the hind limbs.
Palpability of sacrum in a live dog
The sacral region may be palpated with care along the dorsalilip; the sacral crest and sacral wings may be felt in thin or lean dogs; in many dogs the structure is not easily palpable deeply.
One defining feature per species to identify sacral bone origin
Canine: 3 fused sacral vertebrae.
Porcine: 4 fused sacral vertebrae.
Equine: 5 fused sacral vertebrae.
Bovine: 5 fused sacral vertebrae.
Question 9: Specimens: A Typical Canine and an Equine Rib (Page 77)
Origin of the term “rib”
Etymology relates to the curved, curved bones forming the rib cage.
Main features of a typical rib and its costal cartilage
A rib consists of a bony shaft with a costal cartilage anteriorly attaching to the sternum (true ribs) or to the cartilage of the rib above (false ribs) or floating rib without anterior attachment.
Costal cartilage provides flexibility and contributes to the rib cage’s elasticity.
Definitions related to canine rib types
Sternal (true) ribs: ribs with direct joint articulation to the sternum via costal cartilage.
Asternal (false) ribs: ribs that do not directly articulate with the sternum but connect to other costal cartilage chains.
Floating ribs: ribs without any anterior attachment to sternum or other costal cartilage.
Functional parts of the ribcage
The rib bone (osseous part) and the costal cartilage (cartilaginous part) together form the rib cage; the cartilaginous portion allows expansion during respiration.
Question 10: Specimens: Series of Equine Thoracic Vertebrae and an Equine Rib (Page 78)
Two articulations between a rib and the vertebral column
The costo-central joint: rib head articulates with the body of the vertebra (costovertebral joint).
The costo-transverse joint: tubercle of the rib articulates with the transverse process of the same vertebra.
Why these articulations are important
They provide stability while enabling the rib cage to expand and contract during respiration.
Major function of these two articulations
Allow rib movement necessary for ventilation while maintaining thoracic stability; without them, respiration and thoracic support would be compromised.
Question 11: Specimens: Plain Lateral Radiograph of the Canine Thoracic Cavity (Radiograph number 1A) and Skeleton of the Domestic Fowl (chicken) (Page 79)
Three main features of the canine sternum
Median, unpaired sternum with segmented sternebrae; intersternebral fibrocartilage between sternebrae; presence of a radiographically visible sternum with contours across the chest.
Identifying structure labeled “E” on the radiograph, aided by the skeleton
Structure E is a radiographic landmark; in practice, E could correspond to a mediastinal structure or organ outline; use skeletal landmarks to correlate (the exact label requires the image).
Name and composition of structure labeled “C” on the radiograph
C is a branch of the pulmonary vessels seen in the lung field; specifically, the tapering branches of the pulmonary artery rather than the coronary artery.
Definition and function of an intersternebral fibrocartilage
Intersternebral fibrocartilage is the fibrocartilaginous joint material between sternebrae that allows slight flexion and articulation; provides flexibility to the sternum.
Observing intersternebral fibrocartilages on radiographs
They may be visible as the space or density change between sternebrae; radiographs can reveal their presence as a continuity gap or a distinct line depending on the view.
Why the fowl sternum differs from the dog’s sternum
The domestic fowl has a median, unpaired, non-segmented sternum (no sternebrae) with a single sternum bone; absence of intersternebral fibrocartilage.
Value of a segmented sternum in a dog
Segmented sternebrae with intersternebral fibrocartilage allow slight flexibility and growth; the segmentation provides a role in rib articulation and chest expansion.
Value of an unsegmented sternum in a chicken
A single, unsegmented sternum provides structural rigidity without intersternebral joints, consistent with avian flight biomechanics and differing respiratory mechanics.
Two components of an intervertebral disc; visibility on radiographs
Anulus fibrosus and nucleus pulposus; on normal radiographs they are not distinctly visible because discs are radiolucent and soft tissue density.
Structure labelled A on the radiograph and its radiographic significance
A is the trachea; radiographically, it appears as a radiolucent tubular structure in the mediastinum.
Is it normal for the heart (labeled D) to contact the sternum on radiographs?
Depending on thoracic conformation and projection, the cardiac silhouette can approach or contact the sternum; this is sometimes visible on lateral views and is not inherently abnormal.
Structure labelled 8 (challenge to identify without the image)
The label 8 on the radiograph would correspond to another thoracic structure; refer to the image in your notes to identify (e.g., a vascular or organ landmark depending on the view).
Why is the tubular structure labelled F black (radiolucent) – what is it?
F is a tubular radiolucent structure; likely the esophagus or a gas-filled tubular organ; the radiolucency indicates air or gas within the lumen.
Cranial vs canine sternum differences observed on the radiographs
Compare the cranial aspect: canine sternum shows segmented sternebrae with intersternebral fibrocartilage, whereas the avian sternum is unsegmented and lacks sternebrae.
Question 12: Specimens: (a) Canine Femur (b) Plain lateral Radiograph of Canine Arm Region (Radiograph labelled 1) (Page 81-82)
Canine femur: classification and features
Classify as a long bone; identify:
Diaphysis (shaft)
Proximal epiphysis
Distal epiphysis
Proximal metaphysis
Distal metaphysis
Which anatomical feature is not exhibited by the canine femur?
Options include tuberosities, cochlea, trochlea, medial and lateral condyles, and a head; the correct feature not exhibited would need to be identified from the image (e.g., cochlea is not a feature of the femur).
Radiograph shows fracture of which bone?
The image demonstrates a fracture in the femur, with cortical and medullary changes described.
Explanation of bone tissue in diaphysis vs epiphyses/metaphyses
Diaphysis: dense, compact cortical bone surrounding a less dense medullary cavity.
Epiphyses/metaphyses: spongy (trabecular) bone with trabeculae; medullary cavity tends to be smaller.
Functions of the medullary cavity
Houses bone marrow (red and/or yellow marrow) and supports metabolically active tissue; stores fat; participates in hematopoiesis (in red marrow regions during development).
Radiographic identification of shoulder joint cavity (shoulder joint)
The shoulder (glenohumeral) joint is a synovial joint; radiographically, the joint space may be visible; on a plain radiograph, the joint capsule is not easily seen, but the delineation of the proximal humerus and scapula is evident.
Radiopaque marker knowledge
The marker is highly radiopaque and used to identify orientation (left side in the image).
Question 13: Specimens: A Canine Stifle (Knee) Joint and a Plain Lateral Radiograph of the Canine Stifle Joint (Radiograph Number 92) (Page 83)
Define a joint or articulation
A junction where two or more bones meet, allowing movement or stability depending on joint type.
The three major types of joints, with examples and function
Fibrous joints: immovable (e.g., skull sutures).
Cartilaginous joints: limited movement (e.g., pubic symphysis).
Synovial joints: freely movable with a synovial cavity (e.g., stifle, elbow).
Draw a typical synovial joint; function of each part
Include articular cartilage, joint capsule, synovial membrane, synovial fluid, ligaments, and the periosteum.
Movements available in movable (synovial) joints
Flexion, extension, abduction, adduction, rotation, circumduction, etc.
Define and function of tendon and ligament
Tendon: connect muscle to bone, transmitting muscular force.
Ligament: connect bone to bone, stabilizing joints.
Radiograph annotation: cortical bone, medullary cavity, patella, fabellae, etc.
The radiograph demonstrates the diaphysis cortex, medullary cavity, patella within the tendon of the quadriceps, fabellae (sesamoid bones in the stifle region), and the tibia and fibula.
Question 14: Specimen: Canine Skeleton (Page 84)
Define the term sesamoid bone and two major functions
Sesamoid bone: a bone embedded within a tendon or in close association with a joint, typically to modify pressure, reduce friction, and improve muscle leverage.
Functions: alter the angle and leverage of tendons for improved efficiency and protection of tendons from wear.
Largest sesamoid bone in domestic animals and its functional role
The patella (kneecap) is the largest sesamoid bone; it acts to increase the leverage of the quadriceps tendon and protect the knee joint; mobility is critical for locomotion.
Counts of sesamoid bones in canine forepaw and hind paw; are they the same?
Forepaw has a certain number of sesamoids (e.g., several on the digits and around joints); hind paw likewise; the exact counts may differ; the exercise asks to compare and reason about symmetry and function.
Draw and describe synovial bursae and synovial sheaths; clinical significance
Bursae and tendon sheaths reduce friction between moving parts; pathologies include bursitis and tenosynovitis.
Five obvious lever points in the limbs of the canine skeleton
a. Greater tubercle of the humerus (shoulder point)
b. Olecranon of the ulna (elbow point)
c. Greater trochanter of the femur (hip point)
d. Tibial tuberosity (stifle/knee region)
e. Calcanean tuberosity (calcaneus; point of the hock)
Identify the four weight-bearing metacarpal long bones and the four weight-bearing metatarsal long bones
Forepaw: four weight-bearing metacarpals (MC I–IV; depending on species and digit numbering in the deck); Hind paw: four weight-bearing metatarsals (MT I–IV).
Names of the three phalanges forming a digit (what is meant by “phalanx”)
Proximal, middle, and distal phalanges; digits typically consist of phalanges with respective numbers depending on the digit.
Classify the canine scapula (five bone types)
Scapula is a flat bone; among five generic bone classifications, it is a flat bone.
Functions of the scapula
Provides a broad, muscularly attached surface for shoulder movement; acts as part of the shoulder girdle to transfer load from the limb to the axial skeleton; serves as an attachment site for muscles.
Similar bone types elsewhere in the skeleton and their functions
The scapula-like flat bones elsewhere serve protective roles and surfaces for muscle attachment; each flat bone has a protective or surface-based function.
The scapula functions reiteration
The scapula provides the shoulder girdle’s articulation with the humerus and a site for muscle attachments necessary for limb movement.
Additional notes on bone types and functions
A general reminder to review how bone types (long, short, flat, irregular, sesamoid) relate to their specific roles in the skeleton.
Question 16: Specimen: Plain Lateral Radiograph of the Canine Thoracic Cavity (Radiograph labelled 1) (Page 86)
Radiographic opacities and colors
Metal: white; Bone: near white; Soft tissue: grey; Air: black; Fat: darker than soft tissue but not as black as air.
Practical interpretation of the radiograph
Identify ribs as bone opacity; assess for fractures.
Identify the cardiac silhouette (D) as soft tissue opacity; observe lungs as air-filled fields.
Observing branching/pulmonary vessels within the lung fields.
Plain radiograph definition
An X-ray image taken without contrast agents.
Radiographic structures labelled A, B, C, etc.
A: Trachea (radiolucent tubular structure).
B: A likely mediastinal or adjacent structure to be identified in relation to the radiographic view.
C: A branch of the pulmonary vessels (not the coronary artery).
Intersternebral fibrocartilage observation and sternebrae counting
The dog’s sternum is composed of several sternebrae (typically eight sternebrae in the dog); between sternebrae there are intersternebral fibrocartilages; radiographic radiolucent spaces between sternebrae correspond to these joints.
Structure labelled G and sternebrae
G marks a sternebra; dog sternebrae are eight in number; the area between sternebrae shows radiolucent spaces associated with intersternebral discs.
Intervertebral disc between sternebrae (H)
H is the intersternebral fibrocartilage disc between sternebrae which appears radiolucent due to its fibrocartilaginous composition.
Cranial vs canine sternum differences on radiographs
Canine sternum is segmented with sternebrae; avian sternum is unsegmented with a different radiographic appearance.
Significance of radiographic density and structure to clinical interpretation
Radiographic opacity differences are essential for interpreting structures (lungs, heart, bones, vessels, and additional soft tissues).
Question 17: Specimen: Plain Lateral (Side View) Radiograph of the Canine Abdomen and Pelvis (Radiograph labelled 13 B) (Page 87)
Evidence of abdominal contents on radiographs
Gas within stomach and loops of jejunum; faecal matter in the descending colon; visible soft tissue outlines of liver and abdominal organs; intestinal gas outlines help identify organ borders.
Evidence of pregnancy in a dog on radiographs
The radiograph can reveal gas-filled loops; fetal outlines may appear as soft-tissue densities in the uterus depending on gestational stage.
Number of lumbar vertebrae as seen in the radiograph
Locate T13 and count caudally to identify L1 through L7 (typical for the dog). The question prompts identifying L7 as the last lumbar vertebra in the sequence.
Thoracic vertebrae and rib count correlation in domestic animals
In dogs, there are typically 13 thoracic vertebrae and 13 pairs of ribs; horses have 18 thoracic vertebrae and 18 ribs.
Visible liver and its relation to the costal arch
The liver extends caudally beyond the costal arch in the canine abdomen; radiographic outlines show liver silhouette close to the costal arch.
Structure labelled (red dot) in the image
The red dot highlights the tibia/femur region or a target region in the hind limb; refer to the image for precise labeling.
Thoracic viscera and the heart/lung relationship
In a lateral view, the caudal lung fields are visible as air-filled regions; the cardiac silhouette lies within soft tissue density and can be visualized against the lung fields.
Question 18: Specimen: Ventro-dorsal Radiograph of the Canine Abdomen and Pelvis with the Introduction of a Contrast Medium (Radiograph labelled 14) (Page 89)
Define the term “contrast medium”
A substance introduced into the body to increase radiographic contrast between structures; can be positive (radiopaque) or negative (radiolucent).
Types of contrast media
Positive contrast: highly radiopaque (e.g., Barium sulfate, iodinated compounds).
Negative contrast: radiolucent (e.g., air).
Purpose of the radiograph with oral barium sulfate
To highlight the stomach and duodenum by increasing their radiographic opacity.
Clinical interpretation: nephrogram vs pyelogram
Nephrogram: radiograph taken while contrast is in the kidneys.
Pyelogram: radiograph taken when contrast has progressed into the collecting system (renal pelvis and ureter).
Structures highlighted by the contrast radiograph
The gastric outline with the barium; tracer outlines in the urinary tract (kidneys, ureters, bladder) as the contrast moves through.
Question 19: Specimen: Plain Lateral Radiograph of the Canine Abdomen and Pelvis (Radiograph labelled 19D) (Page 90)
Main feature shown on this radiograph
Abdominal contents appear as soft tissue density; gas within the stomach and intestines may be visible; pregnancy-related features may be present depending on stage.
Length of pregnancy in the bitch
Approximately 60 days (roughly 2 months) as one option; standard gestation in dogs is around 63 days; the question provides 60, 90, 120-day options.
How to count fetuses on radiographs
Identify fetal outlines; count the number of fetuses; assess presence of membranes and placentation if visible.
Position of the pregnant uterus in the latter half of pregnancy
The uterus generally occupies a cranial and middle abdomen with the uterus expanding; in the latter half, the uterus occupies a substantial portion of the abdomen.
Comparative pregnancy lengths in other species (approximate values)
Mare ~ 335 days (11 months)
Cow ~ 282 days (9 months)
Ewe ~ 148 days (5 months)
Sow ~ 115 days (4 months)
Bitch ~ 60 days (2 months) [approximate]
Cat ~ 63 days (2 months)
Rabbit ~ 32 days
Rat ~ 22 days
Question 20: Specimen: Ventro-dorsal Radiograph with Contrast Medium Introduced (Radiograph 31C) (Page 91)
Positive contrast medium visualization
Iodine-based contrast highlights the collecting duct system after absorption and excretion by the kidneys; the image on this radiograph shows the path of contrast through the urinary tract.
Definitions of nephrogram vs pyelogram in relation to contrast in the kidneys
If the radiograph is taken while the iodine is in the kidneys, it is a nephrogram.
If the radiograph is taken after the contrast has progressed into the collecting ducts and renal pelvis, it is a pyelogram.
Identify structures in the collecting duct system
Structures labeled 1, 2, 4 correspond to segments of the collecting system; exact labels depend on the image, but they trace the path from the kidney pelvis through calyces and ureter.
Additional radiographic observations
Gas in the gastrointestinal tract; spleen location (left side); the kidney positions (which is more cranial); the last rib attached to the last thoracic vertebra and the corresponding lumbar vertebra; the renal crest and calyces visible in iodinated studies; recesses (renal pelvis diverticula) may be highlighted by contrast.
Clinical significance of the renal crest and papilla
The renal crest (common renal papilla) is an important collecting structure; contrast radiography highlights this feature for renal anatomy evaluation.
Important radiographic landmarks and interpretation tips
Recognize the relative positions of the stomach, liver, diaphragm, and heart on ventro-dorsal views with iodinated contrast.
Summary of key concepts and connections
Vertebral anatomy cross-links
The cervical, thoracic, lumbar, sacral, and caudal vertebrae form a structured axis with region-specific features (cervical transverse foramina, thoracic costal facets, lumbar mass, sacral fusion, etc.).
The vertebral formulae provide a compact summary of regional counts for dog and horse and are essential for identifying species and vertebral region on radiographs.
Joints and disc anatomy
Intervertebral discs (annulus fibrosus and nucleus pulposus) differ from intersternebral joints in the sternum; discs are absent at certain joints (occipito-atlantal, atlanto-axial, and sacral region) per the exam clues.
Radiography fundamentals
Understanding radiographic opacities (metal/bone/soft tissue/fat/air) and how contrast media alter visibility of anatomy (nephrogram vs pyelogram; positive vs negative contrast).
Anatomy-light interpretation: identifying structures such as trachea (A), heart (D), pulmonary branches (C), sternum (G) with sternebrae, and intersternebral discs (H).
Functional anatomy and clinical implications
How vertebral articulations influence movement (flexion/extension vs lateral movement), rib articulations for respiration, and sacral connections for weight transfer to hind limbs.
Species diversity in skeletal anatomy
Differences across dog, horse, bovine, porcine, and avian species in counts (cervical, thoracic, lumbar, sacral, caudal) and in sternum segmentation (segmented sternebrae vs unsegmented sternum).
Practical exam-style expectations
Be able to identify vertebral regions, atypical vertebrae (atlas/axis/anticlinal), radiographic landmarks, and the clinical implications of spinal anatomy (e.g., slipped discs, disc absence zones, and sacral-pelvic attachment).