Skeletal System Bones PDF

The Skeletal System - The Axial & Appendicular Skeleton NSCI5720 Vertebrate Anatomy & Physiology Learning Objectives Be able to name and identify the main bones in the body Name the major divisions and organisation of vertebrate skeleton Division of the Skeleton The b...

The Skeletal System - The Axial & Appendicular Skeleton NSCI5720 Vertebrate Anatomy & Physiology Learning Objectives Be able to name and identify the main bones in the body Name the major divisions and organisation of vertebrate skeleton Division of the Skeleton The bones of the skeleton can be divided into two groups: Axial Skeleton Appendicular Skeleton Division of the Skeleton Axial Skeleton Bones of the head & trunk Located along the central axis of the body Skull, the hyoid bone, the spinal column, the ribs, and the sternum Appendicular Skeleton Bones of the limbs Limbs are appendages of the trunk Skull (Axial Skeleton) Made up of 37-38 bones in our domestic animals! These bones are held together by fibrous immovable joints called sutures. Only the mandible (lower jaw) is connected to the rest of the skull by a freely movable synovial joint Complex: so we group the bones into regions ⚬ Bones of the cranium ⚬ Bones of the ear ⚬ Bones of the face Skull (Axial Skeleton) Skull - Bones of the Cranium (Axial Skeleton) External Bones of the Cranium Cranium is the part of the skull that surrounds the brain Occipital Bones Interparietal Bones Parietal Bones Temporal Bones Frontal Bones Skull - Bones of the Face (Axial Skeleton) External Bones of the Face: Incisive bones - house the upper inscisor teeth Nasal bones - Form bridge of the nose, huge variety among species and breed in size & shape Maxillary bones - Make up most of the upper jaw (with the incisive bones). Part of hard palate. Lacrimal bones - Form part of the eye orbit. House lacrimal duct for tear drainage) Zygomatic bones - Form part of eye orbit & join with temporal bones to form zygomatic arches (widest part of skull) Mandible - Forms lower jaw, only movable skull bone - joins temporal bone at temporomandibular joint (TMJ). House all bottom teeth. Skull - Bones of the Face (Axial Skeleton) Hyoid bone Axial Skeleton Looks like the letter H with its two legs bent back to form a U-shaped structure. Located high in the neck, just above the larynx, between the caudal ends of the mandible. It supports the base of the tongue, the pharynx, and the larynx and helps the animal swallow. It is usually referred to as a single bone, but it is composed of several individual portions united by cartilage. The Spinal Column Axial Skeleton Also known as the Vertebral Column Made up of individual irregular bones - vertebrae Divided into five regions Individual vertebrae are numbered within each region The Spinal Column Axial Skeleton Vertebrae Made up of the body, arch, and several processes. Vertebrae are separated by intervertebral discs (fibrocartilage) - shock absorbers. The arch houses the spinal cord. The processes are sites for muscle attachment and provide leverage for movement. Each vertebrae joint allows limited movement but the whole spine has considerable flexibility! The Spinal Column Axial Skeleton Vertebrae Regions Cervical Thoracic Lumbar Sacral Caudal (Coccygeal) The Spinal Column Axial Skeleton The Spinal Column - Cervical Vertebrae Axial Skeleton Neck region 7 vertebrae in dogs and cats C1 = Atlas, C2 = Axis, rest of cervical vertebrae are similar and numbered like the rest of the vertebrae Atlas has “Wings of the Atlas” (transverse processes) and holds up the head Axis - spinous processess project dorsally and peglike “dens” fit into the atlas to form the atlantoaxial joint (allows pivot-like side to side movement) The Spinal Column - Thoracic Vertebrae Axial Skeleton Thoracic Vertebrae Located dorsal to the thorax (chest) Animals usually have the same number as pairs of ribs Have very tall, spinous processes Their lateral facets form joints with the ribs The Spinal Column - Lumbar Vertebrae Axial Skeleton Lumbar Vertebra Dorsal to abdominal region Have large, bulky bodies to support the abdominal contents (compared with the thoracic vertebrae which have the support of the ribs) The Spinal Column - Sacral Vertebrae Axial Skeleton Sacral Vertebrae Located dorsal to the pelvic region Forms a joint with the pelvis on each side called the sacroiliac joint. Sacral vertebrae are unique in that they fuse to form a single solid structure called the sacrum. The Spinal Column - Caudal (Coccygeal Vertebrae) Axial Skeleton Caudal (Coccygeal) Vertebrae Form the bones of the tail Number and appearance varies greatly between and within a species and even within an individual! In human these are fused to form the coccyx or “tailbone” Ribs Axial Skeleton Flat bones, form lateral part of thorax The number of pairs of ribs usually equals the number of thoracic vertebrae. Dorsal ends: the heads of the ribs form joints with the thoracic vertebrae > freely movable joints help the process of ventilation. Ventral ends of the ribs have two parts: a dorsal part, made of bone, and a ventral part, made of cartilage. ⚬ The cartilaginous part is called the costal cartilage, and its junction with the bony part is called the costochondral junction. The costal cartilages either join the sternum directly or join the costal cartilage ahead of them Cranial part of thorax = sternal ribs Caudal part of the thorax = asternal ribs (join adjacent costal cartilage) The cartilages of the last ribs may not join anything at all = floating ribs. Sternum Axial Skeleton Also known as “breastbone” Forms floor of the thorax Made up of bones called sternebrae Only first and last sternebrae are named and used as landmarks, the rest are numbered. The most cranial = the manubrium The most caudal = the xiphoid or xiphoid process Appendicular Skeleton Appendicular Skeleton Made up of the bones of the main appendages of the animal i.e. the limbs ⚬ The forelimb is termed the thoracic limb ⚬ The hindlimb is termed the pelvic limb Thoracic Limb Appendicular Skeleton Scapula Humerus Radius Ulna Carpal bones Metacarpal bones Phalanges Scapula Appendicular Skeleton Most proximal bone of the thoracic limb Flat, somewhat triangular bone with a prominent, longitudinal ridge on its lateral surface - the “spine of the scapula”. At its distal end, it forms the socket portion of the ball-and-socket shoulder joint. Humerus Appendicular Skeleton The long bone of the upper arm (brachium) Proximal end = ball and socket shoulder joint Distal end = elbow joint with radius and ulna. Ulna Appendicular Skeleton Forms the Antebrachium (forearm) with the radius. Forms part of the elbow joint with the distal end of the humerus. Proximal end - ⚬ Olecranon process - forms point of the elbow ⚬ Anconeal process - forms back surface of elbow, stabilises elbow during weight bearing. Distal end articulates with the carpus. Radius Appendicular Skeleton The main weight-bearing bone of the antebrachium (forearm) Proximal end articulates with the proximal end of the ulna and also joins with the distal end of the humerus. Shaft varies from fairly straight in cats and cattle to somewhat bowed in dogs, horses, and swine. Distal end articulates with the carpus. Carpus Appendicular Skeleton Carpus = Two rows of carpal bones ⚬ Proximal row ￭ Radial carpal bone, ulnar carpal bone, accessory carpal bone. ⚬ Distal row ￭ These bones are numbered instead of named, starting at the medial side and working laterally. Metacarpus Appendicular Skeleton The metacarpal bones extend distally from the distal row of carpal bones to the proximal phalanges of the digits. Dogs and cats typically have five digits or toes making up their front paws. Dogs have five metacarpal bones that are numbered from medial to lateral. Metacarpal I the most medial and is commonly known as the “dewclaw”. The others metacarpals are numbered II, III, IV, and V with Metacarpal V is the most lateral metacarpal. Phalanges Appendicular Skeleton “Digit” = toe (human = finger) Each digit is made up of 2-3 bones called phalanges (singular = phalynx). “Phalanges” = the individual bones that make up the digits. Phalanges Appendicular Skeleton Dog and cat forepaws contain bones similar to human fingers. Digit 1 (the dewclaw) contains two bones: a proximal phalanx and a distal phalanx (similar to our thumb) Digits II to V each contain three bones: a proximal phalanx, a middle phalanx, and a distal phalanx. Each distal phalanx contains a pointed ungual process that is surrounded by the claw. The digits of dogs and cats also contain tiny sesamoid bones: ⚬ Rarely of clinical significance except in performance dogs, (e.g. racing Greyhounds), and heavy large-breed dogs, such as St. Bernards. These heavy breeds can fracture sesamoid bones by jumping. Appendicular Skeleton Pelvic Limb Appendicular Skeleton Pelvis Femur Patella Fabellae Tibia Fibula Tarsus (hock) Metatarsus Phalanges Pelvis Appendicular Skeleton Develops as 3x separate bones on each side that eventually fuse into a solid structure. Two halves are joined ventrally by a cartilaginous joint called the pelvic symphysis. Pelvis joins the axial skeleton dorsally at the sacroiliac joints (one on each side). Though fused, the names of the bones are still used to designate the main regions of the pelvis - ilium, ischium, pubis. Pelvis Pelvis Appendicular Skeleton Functions: Weight-bearing from hindlimbs. Protects and supports the intestines, bladder, and internal sex organs. Pelvis - Ilium Appendicular Skeleton Most cranial bone of the pelvis It projects up in a dorsocranial direction and is the bone that forms the sacroiliac joints with the sacrum. In dogs and cats, the smooth “wing” of the ilium projects forward and is easily felt as a landmark in living animals. Pelvis - Ischium Appendicular Skeleton The ischium is the caudal-most pelvic bone. The main, rear-projecting process of the ischium is the ischial tuberosity Pelvis - Pubis Appendicular Skeleton The smallest of the three pelvic bones. Located medially and forms the cranial portion of the pelvic floor, while the ischium forms the caudal part. Pelvis - Other Notable Structures Appendicular Skeleton Pelvic/Pubic Symphysis: ⚬ Cartilaginous joint that ossifies with age and joins the two sides of the pelvis together ventrally. ⚬ Faciliates the passage of the foetus through parturition (birth). Acetabulum: ⚬ The three bones of the pelvis come together here to form the concave ball-and-socket hip joint that tightly encloses the head of the femur. Obturator foramina: ⚬ Large holes on either side of the pelvic symphysis. Why? = Their function is to lighten the pelvis. Femur Appendicular Skeleton Long bone of the thigh Proximal end: ⚬ Ball portion of ball-and-socket hip joint called the head of the femur. Very deep, secure joint. ⚬ Large processes e.g. Greater Trochanter where hip and thigh muscles attach. Straight shaft Distal end = ⚬ Forms the stifle joint with the patella and tibia. ⚬ Medial & Lateral condyles (caudal) which articulate with proximal end of fibia. ⚬ Trochlea (cranial) where patella lies. ⚬ Medial and lateral epicondyles are “knobs” that are are easily palpated and can be used as landmarks on living animals. Femur Patella Appendicular Skeleton The patella or kneecap is the largest sesamoid bone in the body. It is formed in the distal tendon of the large quadriceps femoris muscle on the cranial aspect of the stifle joint. It helps protect the tendon as it passes down over the trochlea of the femur to insert on the tibial crest. Tibia Appendicular Skeleton Main weight-bearing bone of the lower leg. Proximally: Forms stifle joint with femur above. ⚬ Proximal end appears triangular. ⚬ Forward-facing point of the triangle is the tibial tuberosity where the patellar ligament attaches. This continues distally to form a ridge called the tibial crest. Distally: Forms the hock with the tarsus below. Fibula Appendicular Skeleton A thin bone in dogs and cats that parallels the tibia. It does not support any significant weight but mainly serves as a muscle attachment site. At its distal end, the fibula forms a palpable process called the lateral malleolus. The lateral knob of our ankle is our lateral malleolus. Tarsus (hock) Appendicular Skeleton Known as the hock in four-legged animals (humans = ankle). Two rows of short bones (tarsal bones). Proximal row of bones is named, and the distal row is numbered (from medial to lateral like the carpal bones). Tibial tarsal bone and the fibular tarsal bone = largest proximal bones. Also a smaller, central tarsal bone. The tibial tarsal bone has a large trochlea that articulates with the distal end of the tibia to form the most movable part of the hock joint. The calcaneal tuberosity of the fibular tarsal bone projects upward and backward to form the point of the hock. It acts as the point of muscle attachment and corresponds to our heel. Metatarsus Appendicular Skeleton Almost the same as the metacarpal bones. The main difference is that there are usually only four digits making up the paw on the hindleg so only four metatarsal bones: II to V (as no “dew claw or metatarsal I). In humans these are the bones of our feet. Phalanges Appendicular Skeleton The phalanges of the pelvic limb are almost exactly like the phalanges of the thoracic limb. The only major difference is usually only four digits make up the paw on each hind leg: digits II through V Visceral Skeleton - Os Penis The visceral skeleton consists of bones that form in soft organs or viscera. It is the strangest division of the skeleton and the most variable. Not all animals have visceral bones - they are pretty unusual! The os penis is a bone in the penis of dogs that partially surrounds the penile portion of the urethra. The urethral groove on the ventral surface of the bone encloses the dorsal portion of the urethra. Recap What division of the skeleton does this belong to and what are the joints called between the bones? Recap What is the name of this bone and what division of the skeleton does this belong to? Recap Can you name the five regions of the spinal column?  Recap What division is this part of? Can you name the parts?  Recap What division is this part of? Can you name the parts?  Recap What division of the skeleton is highlighted? Can you name each of the main bones from proximal to distal?  Recap What division of the skeleton is highlighted? Can you name each of the main bones from proximal to distal?