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
