Vertebrae and Skull Structures in Vertebrates: Functions, Types, and Evolution

What are the primary functions of vertebrae?

Protection for the spinal cord, centralized support for the body, and rigid attachment sites for muscles.

What is the central part of a vertebra called?

Centrum.

What are the projections on a vertebra referred to as?

Apophyses.

What is the shape of a true vertebra's body?

Central spool-shaped body with one or more projections.

What type of vertebrae do fish have?

Amphicoelous vertebrae.

What is a unique feature of tetrapod vertebrae in snakes?

An extra set of zygapophyses to resist torsion.

What adaptation do bird vertebrae have for flight?

Lack of flexibility (except neck) and a synsacrum, which is the fusion of certain vertebrae.

What is the function of the chondrocranium?

To protect the brain.

What are the three major components of the skull?

Chondrocranium, splanchnocranium, and dermatocranium.

What is the splanchnocranium derived from?

Gill derivatives, including jaws and the hyoid arch.

What distinguishes chondrichthyan skulls?

They mainly consist of chondrocranium and lack dermal bone.

What type of skull do most reptiles have?

Diapsid skulls, which have two openings (fenestrae).

What is a characteristic feature of alligator skulls?

A long secondary palate that separates the nasal passage from the mouth.

What type of skulls do mammals have?

Synapsid skulls, which have one fenestra.

What should students focus on in the lab regarding vertebrae and skulls?

Identifying specified bones in different skulls, including those of the shark, Necturus, cat, bowfin, and alligator.

What is the significance of the vertebrae and skulls presented in the lab?

They will appear on the practical exam, so students need to know the locations of all bones and cartilage.

What are Haversian systems?

Circular structures in bone composed of a central canal containing blood vessels and nerves, surrounded by concentric rings of bone.

What are osteocytes?

Bone cells that lie in small cavities called lacunae within the bone.

What is the role of osteoblasts?

Cells that actively lay down new bone along the periphery of the bone.

What characterizes dermal bone?

It forms from connective tissue and contains osteocytes within the bone.

What is endochondral bone?

Bone formed through the process of ossification where cartilage is replaced by bone, typically seen in limb bones.

What are the three primary functions of the vertebral skeleton?

1) Protects the spinal cord, 2) Provides centralized support for the body, 3) Serves as a rigid attachment site for muscles.

What are true vertebrae characterized by?

A central spool-shaped body (centrum) and one or more projections (apophyses).

What type of vertebrae is amphicoelous?

Vertebrae with both ends concave, found in sharks, teleosts, and some amphibians.

What type of vertebrae is procoelous?

Vertebrae with a concave cranial end, found in some amphibians and modern reptiles.

What is the significance of zygapophyses in tetrapod vertebrae?

They provide strength and stability to the vertebral column as vertebrates transitioned to land.

What is the synsacrum in birds?

A rigid unit formed by the fusion of posterior thoracic, lumbar, and sacral vertebrae, enhancing strength during flight.

What are the main vertebral regions in mammals?

Cervical, trunk, sacral, and caudal regions.

What is the function of the occipital region of the skull?

It comprises the back of the skull and includes elements that articulate with the vertebral column.

What are the five regions of the chondrocranium?

Occipital, sphenoid, otic capsule, optic capsule, and nasal/olfactory capsule.

What is the role of the basioccipital and exoccipitals in the skull?

They form the occipital condyle(s) for articulation with the vertebral column.

How do vertebrae vary among different vertebrate groups?

Vertebrae range from simple cartilaginous forms in primitive species to complex bony structures in reptiles and mammals.

What is the role of the neural arch?

It surrounds the neural tube and protects the spinal cord.

What are hemal spines and arches?

Structures associated with caudal vertebrae that protect blood vessels.

What is the significance of the parapophysis in mammals?

It lies between two adjacent vertebrae, differing from its position in other vertebrates.

What adaptations do reptiles have in their vertebrae?

They possess additional zygapophyses to prevent excessive torsion.

What is hypertrophic cartilage?

A region where calcium salts begin to deposit during the ossification process in endochondral bone.

What is the function of the urostyle in frogs?

It is a fused structure that supports the pelvic region.

What is the role of the hypapophyses in vertebrae?

They provide additional support and stability to the vertebral column.

What bones form the occipital condyle(s) in vertebrates?

The basioccipital and/or the exoccipitals.

What is the foramen magnum?

The opening in the center of the ring through which the spinal cord exits the skull.

What elements comprise the sphenoid region of the braincase?

The median basisphenoid, presphenoid, pleurosphenoids/laterosphenoids, and orbitosphenoids.

How do the sphenoid elements differ between mammals and other vertebrates?

In mammals, the paired alisphenoids replace pleurosphenoids/laterosphenoids and are not homologous.

What is the periotic bone?

A fused structure of the prootic, opisthotic, and epiotic bones.

What is the function of the optic capsule?

It allows free movement of the eyes and forms a sheath around the eyeball.

What is the nasal/olfactory capsule's role in mammals?

It ossifies into the ethmoid bones, including the mesethmoid and turbinals.

What are the three sets of turbinals in mammals?

Ethmo-, naso-, and maxillary turbinals.

What does the splanchnocranium include?

The gill derivatives, including the jaws (mandibular arch) and hyoid arch.

What are the two elements that compose the jaws?

The palatoquadrate and Meckel's cartilage.

How do the jaws evolve across different vertebrate groups?

In Chondrichthyes, both remain unossified; in Osteichthyes, the palatoquadrate ossifies; in tetrapods, the palatoquadrate forms the quadrate bone.

What happens to the hyoid arch in tetrapods?

It loses its function as a mandibular suspensor and the hyomandibula becomes the stapes.

What is the dermatocranium?

The dermal bone covering of the skull, evolutionarily derived from dermal scales.

What are the main bones that surround the chondrocranium?

Nasals, frontals, parietals, and others that may fuse with endochondral bones.

What is the significance of the palatoquadrate in vertebrates?

It contributes to the nasal capsule and forms part of the ethmoid and trabeculae.

What is the role of the Meckel's cartilage in mammals?

It forms the articular bone of the jaw and contributes to the middle ear.

What is the function of the styloid process in mammals?

It is a fusion of a portion of the hyoid to the temporal bone.

What is the relationship between the gill arches and the laryngeal cartilages?

The remaining gill arch elements give rise to the laryngeal cartilages.

What are the key structures to identify in chondrichthyan fish skulls?

Chondrocranium, splanchnocranium, rostrum, eye orbit, and foramen magnum.

What are the differences in dermal bones between chondrichthyan and osteichthyan fish?

Chondrichthyans have fewer large dermal bones, while osteichthyans have many small dermal bones.

What bones are identified in the skull of Amia clava (bowfin)?

Rostropremaxillary, Maxillary, Nasal, Frontal, Parietal, Orbit, Postorbital, Hyomandibular, Quadrate, Opercular series.

What is a key characteristic of Necturus in terms of skeletal structure?

Necturus is a paedomorphic salamander that retains juvenile characteristics in the adult and does not have a maxilla.

What are the main bones to identify in the Necturus skeleton?

Premaxilla, Vomer, Quadrate, Pterygoid, Squamosal, Frontal, Parietal, Frontoparietal, Dentary, Exoccipitals, Splenial.

What is the significance of the hyoid apparatus in amphibians?

The hyoid apparatus consists of portions of the hyoid arch and parts of visceral arches, supporting the external gills.

What skull characteristics are found in anapsid reptiles?

Anapsid reptiles have a skull with a completely covered temporal region by a sheet of bone.

What are the two types of skull fenestration present in modern reptiles?

Diapsid and synapsid conditions.

What bones should be identified in the skull of a snapping turtle?

Premaxilla, Maxilla, Prefrontal, Frontal, Parietal, Jugal, Postorbital, Quadrate, Squamosal, Supraoccipital, Dentary, Articular.

What bones are found in the skull of a green sea turtle?

Premaxilla, Maxilla, Prefrontal, Frontal, Parietal, Jugal, Postorbital, Quadrate, Squamosal, Supraoccipital, Dentary, Articular.

What structures are identified in the skull of diapsid reptiles like alligators?

Premaxilla, Maxilla, Prefrontal, Frontal, Parietal, Squamosal, Pterygoid, Jugal, Quadrate, Palatine, Occipital Condyle, Dentary, Articular.

What is the primary function of the pelvic girdle in primitive fishes?

To act as stabilizers during swimming.

How did the role of the pelvic girdle change as vertebrates moved onto land?

It became a primary element of propulsion and support for the body.

What are the main bones to identify in the cat skull?

Orbit, Temporal fenestra, Premaxilla, Maxilla, Nasal, Frontal, Palatine, Parietal, Temporal, Occipital, Zygomatic arch, Dentary.

What is the significance of the secondary palate in mammals?

It allows for simultaneous breathing and feeding by separating the nasal passage from the oral cavity.

What are the pelvic elements in advanced fishes used for?

They serve as rudders for steering and braking.

What is the Meckelian fenestra?

A remnant of Meckel's cartilage that enters the lower jaw, found in diapsid reptiles.

What are the key components of the hyoid apparatus in amphibians?

Hypohyal, ceratohyal, and parts of visceral arches.

What is the difference between diapsid and synapsid skull conditions?

Diapsid skulls have two temporal fenestrae, while synapsid skulls have one.

What bones are involved in the articulation of the cat's jaw?

Dentary, Articular, and other associated structures.

What is the evolutionary significance of the pelvic girdle in tetrapods?

It represents a key adaptation for terrestrial locomotion.

What is paedomorphic morphology?

A condition where adults retain larval characteristics.

How is the pelvic skeleton of frogs modified for jumping?

It features fusion and elongation of pelvic elements to increase jump duration and force.

Identify the pelvic girdle structures in Necturus.

Ilium, Pubis, Ischium, Femur, Tibia, Fibula, Tarsals, Metatarsals, Phalanges.

What are the key pelvic girdle structures in frogs?

Ilium, Ischium, Pubis, Femur, Tibiofibula, Tarsals, Metatarsals, Phalanges.

What is the significance of the pelvic girdle in reptiles?

It supports locomotion and varies between species like turtles and iguanas.

Identify the pelvic girdle structures in iguanas and turtles.

Iguana: Ilium, Pubis, Ischium, Femur; Turtle: Ilium, Pubis, Ischium, Femur.

What adaptations are seen in the pectoral girdle of birds?

Fusion of the clavicles and interclavicle into the furculum, and modifications for flight.

What are the main structures of the pectoral girdle in mammals?

Scapula, Clavicle, Humerus, Radius, Ulna, Carpals, Metacarpals, Phalanges.

How does the pectoral girdle differ between fishes and tetrapods?

Fishes have a more flexible pectoral girdle for maneuverability, while tetrapods support body weight.

What is the function of the pectoral fin elements in primitive fishes?

They act as dive planes for turning the body.

Identify the pectoral girdle structures in Necturus.

Coracoid, Suprascapular cartilage, Scapula, Glenoid fossa, Humerus, Radius, Ulna, Carpals, Metacarpals, Phalanges.

What are the adaptations of the pectoral girdle in frogs?

Fusion of forearm bones and a robust sternum for jumping.

What is the significance of the unguligrade posture in horses?

It involves walking on the tip of the third digit, adapting for speed and efficiency.

What structures are found in the pectoral girdle of birds?

Scapula, Procoracoid, Furculum, Keel, Sternum, Humerus, Radius, Ulna, Carpometacarpus.

What skeletal adaptations are present in echidnas?

They retain a sprawled stance and have a unique pectoral girdle structure.

What are the key features of the cat's pectoral girdle?

Includes scapula, humerus, radius, ulna, and various fossa for muscle attachment.

What is the role of the obturator foramen in the pelvic girdle?

It allows for the passage of nerves and blood vessels and reduces weight.

What is the function of the keel in birds?

It provides an attachment point for flight muscles.

What is the difference between plantigrade and digitigrade postures?

Plantigrade involves walking on the entire foot, while digitigrade involves walking on the digits.

What adaptations are seen in the limb elements of birds?

Lightened and fused bones for flight efficiency.

How do the pelvic girdles of mammals differ from those of reptiles?

Mammals have an upright stance with limbs oriented vertically, while reptiles have a sprawled stance.

What are the key structures in the pectoral girdle of sharks?

Scapulocoracoid bar, Glenoid surface, Basal pterygiophores, Radial pterygiophores.