Week+7+Phylum+Chordata+and+Bones

Welcome to K103 Lab Week 7Presented by Lynda Bonewald, PhD and Lilian Plotkin, PhDBoth are professors in the Department of Anatomy, Cell Biology, and Physiology at IU Medical School in Indianapolis.Dr. Lynda Bonewald

• Musculoskeletal biologist who has pioneered research in osteocytes and the intricate processes of bone to muscle crosstalk in aging.

• Over 200 publications to her name, contributing significantly to the understanding of bone biology and health.

• Founding director of the Indiana Center for Musculoskeletal Health (ICMH), focusing on improving musculoskeletal health and treatment.

Dr. Lilian Plotkin

• Bone biologist from Argentina specializing in osteoblasts and bone histology, examining their role in bone formation and health.

• Research focuses on sex differences in the skeleton, exploring chromosomal and hormonal contributions to bone density and structure, which can influence susceptibility to diseases such as osteoporosis.

Organism Overview

Overview of Topics Covered in the Lab Session

1. Organization of Animal Life

   • Classification of Animals

     • Parazoa: The simplest animals, such as sponges, lacking true tissues, which function primarily through the diffusion of water for nutrient delivery.

     • Eumetazoa: Animals with true tissues, including a variety of forms such as cnidarians and bilaterians, exhibiting diverse body plans and functions.

   • Choanoflagellates: Recognized as the closest living relatives of animals, providing insights into the evolution of multicellular life from unicellular ancestors.

   • Phylogeny: Understanding the evolutionary history and relationships among various species, aiding in the classification and study of diverse animal forms.

   • Radiata vs. Bilateria:

     • Radiata: Animals displaying radial symmetry, such as cnidarians (jellyfish, corals).

     • Bilateria: Organisms showcasing bilateral symmetry, exemplified by most animal classes, facilitating complex body structure and movement.

   • Body Cavity Types:

     • Acoelomates: Organisms without a body cavity, such as flatworms.

     • Pseudocoelomates: Have a fluid-filled cavity not entirely lined with mesoderm, like roundworms.

     • Coelomates: Possess a true body cavity fully lined with mesoderm, providing space for organ development (e.g., annelids and vertebrates).

   • Gastrulation: A vital process that forms the gut and defines tissue layers during embryonic development, crucial for organogenesis.

   • Segmentation: Refers to the division of the body into repetitive segments, seen in organisms like annelids and arthropods, allowing for specialized functions per segment.

Chordata - Key Features

• Basic Characteristics: The defining feature of chordates is the presence of a notochord, which can develop into the backbone in vertebrates.

• Dorsal nerve cord: This structure develops into the spinal cord, which serves as a critical conduit for signals between the brain and body.

• Closed circulatory system: Enhances the efficiency of oxygen and nutrient transport in bilateral animals.

• Cephalochordata: The closest living relatives of vertebrates, marine organisms providing significant insights into evolutionary transitions from invertebrates to vertebrates.

• Chordate lineage: Began approximately 650-700 million years ago, marked by the emergence of key features like the notochord and dorsal nerve cord.

Subphylum Features

• Cephalochordata:

  • Marine organisms characterized by segmented bodies and a notochord extending throughout their length, illustrating primitive vertebrate characteristics.

  • Utilize oral cirri for sensory functions and feeding, thriving in marine environments.

• Vertebrata:

  • Includes both aquatic and terrestrial organisms featuring a distinct head and trunk supported by a backbone (vertebral column).

  • Exhibits well-developed brains and sensory organs, facilitating complex behaviors and adaptations.

  • Significant groups include reptiles, amphibians, birds, and mammals, each with specialized characteristics and evolutionary history.

Skeletal System Functions

• The skeletal system plays essential roles, including:

  • Support and protection of body structures, providing a framework for the body and safeguarding internal organs.

  • Facilitating movement by serving as attachment points for muscles.

  • Mineral homeostasis, allowing for the storage and release of vital minerals (calcium, phosphorus).

  • Blood cell production in the bone marrow (hematopoiesis), generating red blood cells, white blood cells, and platelets.

  • Triglyceride storage in yellow marrow, functioning as an energy reserve.

• Skeletal classification includes long bones, flat bones, short bones, irregular bones, and sesamoid bones.

Sesamoid Bones

• Examples include the patella (kneecap), these small, round, and flat bone types develop within tendons and help reduce friction and improve leverage for joint movement.

Bone Structure Hierarchy

• Macrostructure: Understanding whole bones, which can range from millimeters to several centimeters in size.

• Mesostructure: Considers both trabecular (spongy) and cortical bone structure, observable at the micrometer level.

• Microstructure: Focuses on Haversian canals and osteon configuration, essential for understanding bone density and health.

• Submicrostructure: Encompasses mineralized collagen fibrils that provide structural integrity to the bone matrix.

• Nanostructure: Involves the arrangement of collagen molecules and mineral crystals, crucial for overall bone strength and functionality.

Joint Classification

• Basic Joint Types:

  • Synovial Joints: Allow a full range of motion; examples include knee and elbow joints, crucial for mobility.

  • Cartilaginous Joints: These joints permit slight movement and include joints between vertebrae, ensuring stability while allowing flexibility.

  • Fibrous Joints: Allow minimal movement; for example, sutures in the skull provide protection while maintaining integrity.

• Advanced Joint Classification:

  • Types of Cartilaginous Joints:

    • Synchondroses: Joints where bones are united by hyaline cartilage, providing a level of flexibility.

    • Symphyses: Joints where bones are connected by fibrocartilage, allowing slight movement while providing shock absorption (e.g., vertebrae).

  • Types of Synovial Joints: Include gliding, angular, and rotational movements based on respective structural configurations allowing for diverse ranges of motion.

• Cartilage Types:

  • Hyaline Cartilage: Found in articular surfaces, key for providing smooth surfaces for joint movement and shock dispersal.

  • Elastic Cartilage: Offers increased flexibility and support found in structures such as the external ear.

  • Fibrocartilage: Tough cartilage that provides support and shock absorption; found in intervertebral discs and the pubic symphysis.

Connective Tissue Composition

• Fibroblasts: Key cells responsible for generating and maintaining collagen and other connective tissue fibers.

• Collagen: Major component of connective tissue providing strength, structure, and flexibility required for various tissues and organs.

Rib Classification

• Rib Types:

  • True Ribs: Ribs 1-7 that connect directly to the sternum, providing vital protection for the thoracic organs.

  • False Ribs: Ribs 8-10; connected indirectly to the sternum via costal cartilage, creating flexibility to the rib cage.

  • Floating Ribs: Ribs 11-12 that do not connect to the sternum, providing structural support while allowing for greater flexibility of the thoracic cavity during respiration.

Pelvic Girdle Structure

• Composed of:

  • Os Coxa: Formed from the fusion of ilium, pubis, and ischium, crucial for weight bearing and movement.

  • Sacrum and Coccyx: Supporting the vertebral column and serving as attachment points for ligaments and muscles.

Activity and Review:

• Identify bones in the lab session, focusing on their orientation and anatomical features.

• Prepare anatomical slides for viewing: Amphioxus immature adult, hyaline cartilage, white fibrous tissue, etc.