Anatomical Landmarks Flashcards
Define CRANIAL
Towards the head
Define CAUDAL
Towards the tail
Define DORSAL
Towards the back
Define VENTRAL
Towards the underside
Define DISTAL
Towards the limbs
Define PROXIMAL
Towards the middle
Define LATERAL
Towards the side
Define ROSTRAL
Towards the nose
Define PALMAR
Towards the underside of the forepaw
Define PLANTER
Towards the underside of the hindpaw
What are the planes of the body?
- Median/midsaggital plane
- Dorsal plane
- Transverse plane
- Sagittal/paramedian plane
They create cross sections in different areas of the body
What are the planes of the body used for?
For MRI and CT scanning. They are not as important for x rays but are still useful to know
Where is the median/midsaggital plane?
It splits the body into left and right equal portions
Where is the transverse plane?
A plane that divides the body into front and back portion. The transverse plane extends down the limbs (think about when the animal is in sternal and the limbs are extended)
Where is the dorsal plane?
Perpendicular to the median plane; divides the body into upper and lower portions
Where is the sagittal/paramedian plane?
The plane when the median plane deviates from the midline. Also applicable to limbs
What are the functions of bone?
- provide structure to the body
- protect soft tissue and internal organs
- allow movement via attachment to muscles
- aids in the production of white and red blood cells
What is bone?
A type of connective tissue. It is the second hardest substance in the body (behind enamel)
Define ERYTHROPOIESIS
The production of red blood cells
What arrangements can bone be found in?
- Compact bone
- Cancellous bone
Where is the medullary cavity?
Within the spongy bone of long bones
Define BONE MARROW
A spongy substance in the centre of bones. It produces white blood cells, red blood cells and platelets
What is compact bone?
AKA cortical bone or cortex. Sits on the outside of the bone, is dense and strong. Creates the hard structures of the skeleton
What is cancellous bone?
AKA spongy bone. Found beneath the cortical bone in all bones, and at the end of long bones. It has aerated pockets. Some species have more than others.
Define ERYTHROCYTES
Red blood cells
What is a young skeleton predominantly made of?
Cartilage
What are some of the components of bone?
Collagen fibres (provide strength), inorganic materials (such as calcium and phosphorus), osteocytes (mature bone cells), and a ground substance of mucopolysaccharide (basically glucosamine)
Define OSSIFICATION
The natural process of bone formation
What are the two ways that ossification can occur?
- intramembranous ossification
- endochondral ossification
Describe intramembranous ossification
The process through which mesenchymal (stem) cells are directly converted into bone. Mesenchymal tissue is present in embryo and may develop into any tissue within the body
Describe endochondral ossification
The process through which growing cartilage is systematically replaced by bone
What are the three types of cells involved in bone development?
Osteoblasts, osteoclasts, and osteocytes
Describe osteoblasts
Builder cells. They are responsible for producing bone, both in embryo and throughout life
Describe osteoclasts
The remodeller cells. They help to remodel bone that has already been created. They break old bone down in the process.
At fracture sites, calluses form
Describe osteocytes
Mature bone cells that were previously osteoblasts. They are stabilised and have a long life span that can be as long as the organism itself. They maintain the bony matrix
Remember - bone is stable and new bone is only created if needed (e.g. in the case of a fracture
Define COLLAGEN
The main structural protein found in skin and other connective tissue, including bone
What is a bone callous?
Forms at a fracture site to create a temporary connection during repair. They start soft and harden over time as the injury heals
Where does intramembranous ossification occur primarily?
It replaces fibrous connective tissue during development of bones in the skull, the maxilla and mandible, the flat bones of the pelvis, and during fracture repair
Define MAXILLA
The upper jaw bone of most vertebrates
Define MANDIBLE
The lower jaw bone of most vertebrates
What are the stages of ossification?
- cartilage is formed in the fetus
- primary centres of ossification form in the diaphysis as osteoblasts start to replace cartilage with bone. This occurs around day 45 of gestation for both cats and dogs
- secondary centres of ossification occur at the epiphyses, and the medullary cavity is formed in the centre of long bones by osteoclasts remodelling the centre of the shaft
- a cartilage ‘sheet’ (the epiphyseal plate/growth plate) These allow for elongation as the bone grows
- the epiphyses are replaced by bone, and eventually fuse after which no further growth is possible - the adult has reached its mature adult size
Define DIAPHYSIS
The shaft, or central part of long bones
Define EPIPHYSIS
The end of a long bone, initially growing separately
What are some of the requirements of bone?
Bones are living tissue - require calcium, vitamin D and protein, phosphorus
Define PARATHYROID HORMONE
Released from the parathyroid glands in the neck - controls calcium, phosphorus, and vitamin D levels.
What controls the amount of calcium present in bone?
Parathyroid hormone and calcitonin (another hormone). They have opposite effects
What does parathyroid hormone control?
Controls calcium, phosphorus, and vitamin D levels. All three work together and are linked
What type of bone has the most erythropoiesis?
Long bones > flat bones. This is because flat bones do not have the same medullary cavity as long bones
What are some of the roles of parathyroid hormone?
- increases osteoclast activity, which breaks down bone and release calcium into circulation
- inhibits the activity of osteoblasts, reducing calcium disposition as a result
- increases release of inorganic phosphate by the kidneys. This leads to a drop in serum phosphate, and then an increase in calcium and phosphate within bone
What is the role of vitamin D within bones?
Helps to regulate body systems. It ensures calcium and phosphorus are usable in the body, stopping them being lost by the patient
Define RICKETTS
Caused by a prolonged vitamin D deficiency, it is the softening/weakening of bones
What are some good sources of vitamin D for animals?
Marine fish, fish oils, and UV (sunlight), although sunlight is fairly inefficient and good dietary supplementation is essential
What is the axial skeleton?
The collection of bones which run dorsal midline from the skull to the tail
What are the components of the axial skeleton?
The skull, the maxilla, the mandible, the cervical vertebrae, the thoracic vertebrae, the lumbar vertebrae, the sacral vertebrae, the coccygeal vertebrae, the ribs, the sternum and the sternebrae
What are some specific bones of the skull?
The cranium, parietal, frontal, palatine and temporal
What are the portions of the spine called?
Cervical, thoracic, lumbar, sacral, coccygeal
How many cervical vertebrae are there?
7
How many thoracic vertebrae are there?
13 pairs, each corresponding with a respective pair of ribs
How many lumbar vertebrae are there?
7
How many sacral vertebrae are there?
3, and 4 in rabbits
What is particular about the sacral vertebrae?
They are fused on to the pelvis
How many coccygeal vertebrae are there?
22 in most species, rabbits have 16
How many ribs are there in cats and dogs?
13 pairs, to match each of the thoracic vertebrae
How many sternebrae are there?
8
Name the most cranial portion of the sternum
The manubrium
What is the xiphoid process?
The most caudal portion of the sternum, it gradually ossifies throughout life.
What is the costochondral junction?
The point on each rib where the ossified bone meets softer bone/cartilage, joining the ribs to the sternum
What different skull types can be seen in small animals?
Mesocephalic, doliocephalic and brachycephalic
What is a mesocephalic skull?
A regular shaped and sized skull, intermediate in width and length. Not particularly disposed to any health conditions
What is a doliocephalic skull?
Extremely long skulls, with long and slender noses. All the bones of the skull are elongated, especially the ones in the jaw. Breadth of the head is less than three quarters of the length
What is a brachycephalic skull?
Short nosed, flat faced, with broad skulls overall. All bones of the skull are shortened
What are some examples of breeds that have a mesocephalic skull?
Beagles, german shepherds, husky, labradors
What are some examples of breeds that have a doliocephalic skull?
Sighthounds, including greyhounds, whippets etc.
Also daschunds
What are some examples of breeds that have a brachycephalic skull?
French bulldogs, pugs, Boston terriers
Describe the cephalic index
The scale to determine the degree of flattening in a skull
Low cephalic index = long slender skull and face
High cephalic index = flat, broad skull and face
What are the key functions of the axial skeleton?
- movement via muscle attachment
- protection of the brain within the skull, spinal cord behind the spine and the thoracic organs within the ribs
- eating and chewing via the use of the maxilla and mandible
Name some key bones of the skull
The nasal bone, the lacrimal bone, the parietal bone, the occipital bone, the temporal bone, the pterygoid bone, the zygomatic bone, the maxilla, the incisive bone
What are some health conditions that brachycephalic breeds are predisposed to?
Brachycephalic obstructive airway syndrome, bulbous eyes, eye ulcers, spinal problems, dystocia
What is the appendicular skeleton?
Describes the bones of the limbs
Name the bones of the forelimb
From top to bottom:
The scapula (shoulder blade - has a large spinous process for muscle attachment)
The humerus
The radius (cranial) and ulna (caudal)
The carpal bones (the wrist)
The metacarpals
The phalanges/digits
What is another name for the forelimb?
The thoracic limb
What is significant about the connection of the forelimb to the thorax?
There is no boney connection - it has a syssarcosis muscle attachment
Define THORAX
The chest. Contains the lungs, heart and other thoracic organs
Define SYSSARCOSIS
A union between parts of the skeleton by muscles alone
Describe the scapula
A flat bone that is roughly triangular, it has a prominent spine separating it into two halves. The distal end has a projection call the acromion and the joint socket is called the glenoid cavity
Define the ACROMION
A projection at the distal end of the scapula, where it meets the clavicle
Define the GLENOID CAVITY
A shallow vertically elongate concavity on the scapula that receives the head of the humerus
Describe the shoulder joint
The articulation between the scapula and the humerus. It is a synovial joint with a ball and socket action
Describe the clavicle
The collar bone, not found in dogs. Found in cats, rabbits and other small herbivores.
What is specific about the clavicle in dogs?
They do not have one
What muscle is the clavicle found within in the cat?
The brachiocephalicus muscle - there is no articulation between the bone and anything else. In cats, the clavicle is said to be vestigial
Define VESTIGIAL
Something that has no real purpose, like the clavicle in cats
Describe the humerus
The first long bone of the thoracic limb. It forms an articulation proximally at the shoulder, and the elbow distally
Describe the radius and ulna
The two bones that form the antebrachium. In the dog and cat they are separate bones, but they are fused in some species such as the rabbit. The radius is the shorter of the two, and articulates with the humerus at the elbow joint, and the carpals at the carpus
Describe the elbow joint
A composite joint, made up of several parts;
the joint of the condyles of the humerus and the head of the radius, the humerus and the ulna, and the proximal joint between the radius and ulna (a pivot joint)
Define CONDYLES
A round protuberance at the end of some bones that forms an articulation with another bone
Define a SYNOVIAL JOINT
A joint characterised by the presence of a fluid filled joint cavity, contained within a fibrous capsule
Where does the brachiocephalicus muscle run from and to?
From the base of the skull to the humerus
What is the antebrachium?
The forearm, the area between the elbow and the carpus
Where does the cephalic vein run?
On the cranial aspect of the forearm
What type of joint is the elbow joint?
A hinge joint - it can only flex and extend, it cannot rotate
What causes the elbow to be a hinge joint?
The joint between the humerus and ulna stablises the joint as a whole
Define FLEXION
To close the angle of a joint
Define EXTENSION
To open the angle of a joint
Describe the carpus and its bones
The carpus is the wrist joint, a plane or gliding synovial joint. 7 bones in total make up the carpus
Describe the metacarpals
Rod shaped bones; 5 in dogs and cats, depending on the presence of a dew claw. Join the carpus to the phalanges
Describe the phalanges
These are the digits, there are 5 in total. Phalange 2-5 have 3 bones in total (proximal, middle and distal phalanx).
Digit 1 (the dew claw - always medial) has no middle phalanx, and the most distal phalange is modified to allow nail growth at the ungual process
How many bones are in the carpus?
7 in total, arranged in two rows
How are the phalanges arranged in a rabbit?
The radius and ulna are distally fused and rabbits only have 4 digits on their hind limb
What is another name for the hind limb?
The pelvic limb
What bones make up the pelvic limb?
The femur, the tibia and fibula, the tarsus, the metatarsals, and the phalanges
How many bones make up the pelvis?
3, they are fused at the articulation of the pelvis (the acetabulum)
What is the acetabulum?
The cup shaped hole in the pelvis to which the hind limb attaches. Also called the cotyloid cavity. The head of the femur meets the pelvis here, forming the hip joint
What is the name of the ligament that stabilises the hip joint?
The Tares ligament
What are the components of the pelvis?
The sacral vertebrae, which are fused to the pelvis
The wings of ileum
The acetabulum
The pubic symphysis (the centre line of the pubis)
The icschiac tuberosities
Define the PUBIC SYMPHYSIS
A cartilaginous joint that connects the two halves of the pelvic bone. It provides stability to the pelvis, ensuring the two halves stay connected and correctly aligned.
What is specific about the pubic symphysis in guinea pigs?
It fuses when the guinea pig reaches maturity, which is only around 1 year old. Mating after this point is not advised due to the likelihood of pups getting stuck in the birth canal
Describe the ichschiac tuberosities
The thickened, caudolateral part of the ischiac table. In domestic animals they are visible landmarks. Colloquially called the sitting bones.
Describe the femur
The first long bone of the hind limb, with many sites for muscle attachment. It articulates with the acetabulum of the pelvis proximally and the tibia distally
Define the GREATER TROCHANTER
A tubercle of the femur near its joint with the hip bone
Define the LESSER TOCHANTER
A conical bony projection from the shaft of the femur
Define FABELLAE
Small sesamoid bones found at the distal end of the femur, specifically in the tendons of the gastrocnemius muscle
Define the SESAMOID BONES
A bone embedded in tissue; tendon or muscle
Give some examples of sesamoid bones
The fabellae of the femur and the patella (kneecap)
Describe the tibia and fibula
Form the mid hind limb, they are fused at the distal end. The fibula is lateral to the tibia, but both articulate distally with the tarsus (hock)
Describe the tarsus
The mid joint of the hind limb, bends backwards.
Made up of 7 bones arranged in 3 rows
What is another name for the tarsus?
The suffrago, although this is a term usually used for birds
How many bones in total are in the tarsus?
7 in total, arranged in 3 rows
What are the three types of locomotion?
plantigrade, digitigrade, unguligrade
Define PLANTIGRADE LOCOMOTION
Locomotion in which the whole surface of the foot is placed on the ground when walking
Define DIGITIGRADE LOCOMOTION
Locomotion where an animal walks on their toes
Define UNGULIGRADE LOCOMOTION
Locomotion involving walking on ‘toenails’ or hooves
What are some examples of species that use plantigrade locomotion?
Humans, bears, the hindlimbs of rabbits
What are some examples of species that use digitigrade locomotion?
Cats and dogs
What are some examples of species that use unguligrade locomotion?
Pigs and horses
What is the lateral malleolus?
A bony projection on the lateral aspect of the distal end of the fibula
What is the medial malleolus?
A bony projection on the medial aspect of the distal tibia
What is the talus?
The medial bone of the the tarsus. Extends caudally to meet the calcaneus to form the hock joint
What is the calcaneus?
The lateral bone of the tarsus Extends caudally to meet the talus to form the hock joint
Define ABDUCTION
To move a limb away from the midline
Define ADDUCTION
To move a limb towards the midline
Define PRONATION
Describes a normal limb in a normal position on a surface
Define SUPINATION
Rotation of the paw/limb inwards
Define CIRCUMDUCTION
Circular movement at the end of the limb only
Define PROTRACTION
The limb is moved away cranially
Define RETRACTION
The protracted limb is moved back to its original position, or further back
Describe a joint
The point at which two bones meet
What is another name for a joint?
An arthrosis
How many classes of joint are there?
Three
What are the three classes of joint?
Fibrous, cartilaginous, synovial
Describe a fibrous joint
These joints have no movement and are found between the bones of the skull
What is a synovial membrane?
The inner layer of the joint capsule, it lines the joint cavity and secretes synovial fluid to lubricate the joint
Describe a cartilaginous joint
Has slight movement. Found at the mandibular symphysis, the pubis, vertebrae, and the costochondral junction
Describe a synovial joint
Freely moving joints found in the appendicular skeleton. The surfaces of the bones are covered in cartilage, and there is a capsular surrounding the joint filled with synovial fluid to reduce friction
Define OSTEOARTHRITIS
Degeneration of joint cartilage and the underlying bone, resulting in pain and stiffness. Common as the animal ages.
Define HYALURONIC ACID
One of the main components of connective tissue, forming a gelatinous matrix that surrounds cells. It acts as a lubricant and a protective cushion. It is found in synovial fluid
What is the function of ligaments?
They can help to stabilise synovial joints, for example the collateral ligaments of the stifle
Define HYALINE CARTILAGE
Glass like cartilage that is found on many joint surfaces. It is smooth and slippery and aids with bones moving smoothly
Define MENISCI
Crescent shaped fibrocartilaginous structures that divide the joint, add concavity and help to stabilize movement
What are the three different types of joint movement?
Synarthrosis (non moving), amphiarthrosis (some, limited movement), diarthrosis (freely moving)
What are intracapsular ligaments?
Ligaments that exist within the joint capsule to stabilise it (as opposed to outside it)
How many different types of synovial joint are there?
5
What are the different types of synovial joint and how are they classified?
Plane/gliding joints, pivot joints, conyloid/ellipsoid joints, hinge joints, spheroidal (ball and socket joints)
They are classified by the shape of the articular surface
Describe a plane/gliding joint
Have limited movement; involve two flat surfaces gliding over each other
Examples: carpus, vertebrae
Describe a pivot joint
Where one bone slots into another and allows rotation
Example: C1 and C2 (atlas and axis)
Describe a conyloid/ellipsoid joint
Where the curved surface of a bone fits into the cupped surface of another
Example: the skull articulating with the first vertebrae
Describe a hinge joint
Allows only one type/direction of movement, but can be wide ranging
Example: the elbow
Describe a spheroidal joint
A ball and socket joint. Movement in all directions is possible.
Examples: the femur and the acetabulum of the pelvis, and the shoulder joint
Define BULLA
A hollow, boney structure on the ventral posterior portion of the skull that encloses parts of the middle and inner ear
Define the TYMPANIC MEMBRANE
The eardrum
How many cavities can the mammalian body be divided into?
Three - thoracic, abdominal and pelvic
Describe the thoracic cavity and its boundaries
The cranial boundary is the thoracic inlet
The caudal boundary is the diaphragm
The lateral boundaries are the ribs
The dorsal boundary is the thoracic vertebrae
The ventral boundary is the sternebrae
Define STERNEBRAE
The unpaired segments of bone which form the sternum. There are 8 in total
What are the contents of the thoracic cavity?
The heart, lungs, trachea, oesophagus, the thymus gland (young animals only), and blood and lymph
Describe the abdominal cavity and its boundaries
The cranial boundary is the diaphragm
The caudal boundary is indiscrete
The dorsal boundary is the lumbar vertebrae
The ventral boundary is the linea alba
The lateral boundary would be skin edges
Define LINEA ALBA
Latin for ‘white line’ - a thin band of connective tissue that runs down the front of the abdomen separating the two sides of the abdominal walls
What are the contents of the abdominal cavity?
The stomach, kidneys, liver, gall bladder, spleen, small and large intestines, the pancreas, nerves and vasculature.
In females it also includes the ovaries and the uterine horns
Describe the pelvic cavity and its boundaries
The cranial boundary is indiscrete
The caudal boundary is the pelvis outlet
The dorsal boundary is the sacral vertebrae
The ventral boundary is the pubic bone
What are the contents of the pelvic cavity?
The bladder, the colon (including the sigmoid colon just before the rectum) and the rectum
In females, the urethra is located in the pelvic cavity (it is externalised in males) and so is the body of the uterus
Define the CRANIUM
The portion of the skull that encloses the brain
Define OCCIPITAL
Refers to the bone that covers the back of the head or skull
Define the FRONTAL REGION
The most superior portion of the face, spreads from the hairline to the eyebrows
Define the PARIETAL REGION
Forms much of the dorsal and lateral walls of the cranium
Define the TEMPORAL REGION
Lies below the parietal bone on the caudolateral aspect of the skull. The most ventral part of the temporal bone forms a rounded prominence called the tympanic bulla, which houses the structures of the middle ear
Define the FORAMEN MAGNUM
A large, oval shaped opening in the occipital bone of the skull through which the spinal cord passes as it exits the cranial cavity
Define the ZYGOMATIC ARCH
An arch of bone that projects laterally from the skull on each side, forming the cheekbone
Define the JUGULAR PROCESS
A bony prominence on the temporal bone - they are good sites for muscle attachment
Define the CORONOID PROCESS
A rounded process in the skull to which the temporalis muscle attaches
Define the PREMAXILLA
A pair of small bones in the very tip of the upper jaw. Also called the incisive bone, it can sometimes bare teeth.
One of the three bones that make up the hard palate
Define the TEMPEROMANDIBULAR JOINT
The joint that connects the mandible to the rest of the skull, allowing the opening and closing of the jaw
Define the MANDIBULAR SYMPHYSIS
The point at which the two halves of the mandible meet - a common fracture site in cats and dogs
Define SYMPHYSIS
A fibrocartilaginous attachment between two bones
Define the OLECRANON
A curved bony protrusion extending the proximal ulna beyond the distal extremity of the humerus. Forms the prominent point of the elbow
Define the ANCONEAL PROCESS
A small projection of the bone on the ulna, it forms the back surface of the elbow joint
Define the LUMBOSACRAL JUNCTION
The point at which the lumbar and sacral vertebrae meet. Injury to this joint can result in cauda equina
Define the SACROILIAC JOINT
The point at which the sacral vertebrae attaches to the pelvis
Define the OBTURATOR FORAMEN
The large, bilaterally paired opening of the pelvis, just below the acetabulum
Define TROCHANTER
Both greater and lesser - tubercles of the femur.
Both sit on the proximal extremity of the femur, the greater lateral, and the lesser medial
Define the PATELLA
The kneecap. A large sesamoid bone
Define the TIBIAL CREST
The top front part of the tibia (the shin)
