Lecture+7_Skeletal

Lecture Overview

  • Lecture #7: The Skeletal System: Teeth and the Axial Skeleton

  • Instructor: Dr. Tara Gaab

  • Course: ANFS240, Spring '25

  • Date: 2/17/25

Teeth and Dental Formulas

  • Importance of Knowing Teeth:

    • Although the dental formula will not be tested, students should recognize individual teeth.

    • "Teefs" refers to the teeth in a colloquial manner.

Types of Teeth

  • Incisors (I):

    • Position: Most rostral (front) teeth.

    • Function: Divide food before ingestion.

    • Note: Upper incisors absent in ruminants (cattle, sheep, goats, etc.).

  • Canines (C):

    • Well-developed in carnivores, deeply embedded in the bone.

  • Premolars (P):

    • Positioned as the rostral cheek teeth.

  • Molars (M):

    • Positioned as the caudal (back) cheek teeth, not easily visible.

Dental Formulas of Different Species

  • Feline Dental Formula:

    • I 3/3, C 1/1, PM 3/2, M 1/1

    • Total Teeth: 30

  • Canine Dental Formula:

    • I 3/3, C 1/1, PM 4/4, M 2/3

    • Total Teeth: 42

  • Equine Dental Formula:

    • I 3/3, C 0(1)/0(1), PM 3(4)/3(4), M 3/3

    • Total Teeth: 36-44 depending on individual variation.

Specialized Dental Structures

  • Carnassial Teeth:

    • Specialized for shearing in carnivores.

    • Identified as P1 (upper) and M3 (lower).

  • Diastema:

    • A gap between teeth, commonly found in herbivores.

  • Dental Pad:

    • Found in ruminants; a tough area where upper incisors are absent.

Deciduous Teeth

  • Definitions:

    • Also known as "baby teeth" or "milk teeth."

    • Typically smaller and fewer than permanent teeth.

    • Eruption: The process in which teeth emerge through the gums.

    • Diphyodont: Animals with a set of deciduous teeth replaced by permanent teeth.

    • Useful in determining the age of juvenile animals.

    • Permanent teeth typically consist of molars in early development.

Paranasal Sinuses

  • Definition:

    • Cavities in the skull filled with a network of air pockets, lined with mucous membranes.

    • Communicate with the nasal cavity; six types:

      1. Frontal

      2. Caudal

      3. Rostral

      4. Ventral

      5. Dorsal

      6. Palatine

Hyoid Apparatus

  • Made up of 5 bones linked by cartilage.

  • Suspends the tongue and larynx from the skull.

  • Important for preventing foreign materials from entering the airway.

Vertebral Anatomy

  • Intervertebral Foramen:

    • Openings that allow spinal nerves to exit.

  • Intervertebral Disks:

    • Fibrocartilaginous tissues between vertebrae.

  • Vertebral Arch:

    • The dorsal portion of a vertebra encompassing the vertebral foramen.

  • Vertebral Body:

    • Thick, rounded, ventral portion; convex cranially and concave caudally.

  • Vertebral Canal:

    • Formed by the alignment of vertebral foramina, housing the spinal cord.

Vertebrae Types

  • Cervical (C): Always 7, consists of:

    • C1 - Atlas: Supports the head; allows "yes" motion; lacks a body and spinous process.

    • C2 - Axis: Features a large spinous process and dens for "no" motion.

    • C3-C7: All have transverse foramina.

  • Thoracic Vertebrae:

    • Articulate with ribs; elongated spinous processes.

  • Lumbar Vertebrae:

    • Varies by species; carnivores typically have 7, equines have 6, ruminants may vary.

  • Sacral Vertebrae:

    • Fused to form the sacrum; connect to hip bones at the sacroiliac joint.

  • Coccygeal Vertebrae:

    • Make up the tail; number varies widely.

Thoracic Anatomy

  • Thorax Contents:

    • Formed by ribs, sternum, and thoracic vertebrae; protects heart, lungs, and parts of the trachea and esophagus.

Ribs

  • Structure:

    • Long, curved bones; arranged in pairs.

    • Articulate with two vertebrae each.

Rib Anatomy Components

  • Head: Articulates with cranial vertebrae.

  • Tubercle: Articulates with transverse processes.

  • Body and Costal Cartilage: Connecting structure to the sternum.

Sternum Structure

  • Composed of three parts:

    • Manubrium: Cranial-most, palpated at the first ribs.

    • Sternebrae: Segments that connect with costal cartilage.

    • Xiphoid Cartilage: Caudal-most, extends out between costal arches.

Rib Categories

  • Vertebrosternal (True Ribs): Directly articulate with the sternum.

  • Vertebrochondral (False Ribs): Indirectly articulate via connections with other ribs.

  • Vertebral (Floating Ribs): Do not connect to the sternum or other ribs directly.

Clavicle Overview

  • Presence varies across species; functions to connect the axial skeleton and forelimbs.

  • Non-functional or vestigial in certain species like cats and dogs; absent in horses.