07 Miner Ali Zed Tissues

Comparative Anatomy of the Vertebrates:

[CHAPTER 7:

Mineralized Tissues: An Introduction to the Skeleton]

OUTLINE: I. Functions of the Skeletal System II. Steps in the Formation of Skeletal Tissues III. Bone Types of Bone based on structure: A. Compact B. Spongy C. Dentin D. Acellular Types of Bone based on development: E. Membrane F. Replacement IV. Cartilage A. Hyaline B. Fibrocartilage C. Elastic D. Calcified V. Skeletal Remodeling VI. Tendons, Ligaments, and Joints VII. Heterotropic bones

o

More or less parallel to the direction of force o Characteristic of amniotes b) Periosteal Bone o Formed on the inner surface of periosteum which covers all except at their articular surfaces SPONGY OR CANCELLOUS BONE a) Trabeculae provides maximum strength o Haversian systems absent b) Marrow in the trabeculae supports blood vessels, nerve fibers and adipose tissues c) Endosteum has the capacity to deposit bone and remodel it ~ Flat Bones: core of spongy bone and marrow sandwiched between two layers of compact surface: sternum, scapulae, skull mem. bones DENTIN

How is the skeleton relevant to comparative anatomy? Because it is left behind in the fossil records I. FUNCTIONS: 1. 2. 3. 4. 5.

Supporting framework for the body Protection of internal organs Muscle attachment/leverage for locomotion Storage of minerals Hematopoiesis (bone marrow)

II. STEPS IN THE FORMATION OF SKELETAL TISSUES 1. 2. 3. 4. 5.

Aggregation of mesenchyme to form blastema Some mesenchyme cells become fibroblasts Synthesis of collagen by fibroblasts The fibrils aggregate to form collagen fibers The fibers form dense collagen bundles that are woven into network of dense CT 6. Deposition of minerals 7. Formation of cartilage or bone III. BONE -

Matrix of collagenous fibers + hydroxyapatite crystals + (water + mucopolysaccharide) Osteoblasts become TRAPPED by the bone they have laid around them Lacunae contains osteocytes Canaliculi present. It houses the protoplasmic processes extending from the osteocytes

COMPACT OR LAMELLAR BONE a) Osteon or Haversian system present (thus, vascularized) o Blood vessels are responsible for the configuration of haversian systems

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Same constituents as bone Odontoblasts are NOT TRAPPED in lacunae during osteogenesis because they RETREAT as they deposit dentin - Leave behind protoplasmic processes called dentinal tubules (canaliculi counterpart) - Dentin forms only in the outer surface of the dermis ~ Placoid scales’ enameloid are odontoblast in origin; scales of basal-ray finned and elasmobranch fishes and in teeth are dentin

ACELLULAR BONE - ASPIDIN - RETREAT as they deposit dentin - Leave behind NO protoplasmic processes ~ Flexible scales of modern fishes and the cementum of the vertebrate teeth MEMBRANE BONE -

Bone deposited DIRECTLY within a membranous blastema through intramembranous ossification - Lacks haversian canals ~ dermal bones: bones of the lower jaw, skull, pectoral girdles; periosteal bone REPLACEMENT BONE -

Deposited where hyaline cartilage already exists through endochondral ossification In ectotherms, chondrogenesus us throughout life; in birds and mammals, centers cease elaborating cartilage after sexual maturity

Comparative Anatomy of the Vertebrates:

[CHAPTER 7:

Mineralized Tissues: An Introduction to the Skeleton]

It must be noted that in both kinds of ossification, the immediate result is formation of temporary spongy bone. IV. CARTILAGE -

Matrix of collagenous fibers + sulfated mucopolysaccharide Chondroblasts become chondrocytes after being TRAPPED in lacunae Canaliculi absent. Blood vessels absent

HYALINE CARTILAGE -

Precursor of replacement bone, hence least differentiated ~ Found chiefly on the articular surfaces of bones within the joints of tetrapods FIBROCARTILAGE -

Thick, dense, collagenous bundles in the interstitial matrix ~ intervertebral discs of mammals

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Directly continuous with the periosteum Holds the bone in their proper alignment in the joint ~ Nuchal ligament is the longest ligament in mammals VS. Falcofrom cartilage = mesenteries; skeletal structures Aponeuroses - Tendons and ligaments that are flat and wide ~ gala aponeurotica of the mammalian scalp Sesamoid cartilages - Mineralized nodules in tendons or ligaments ~ patella 3. JOINT OR ARTHROSIS -

ELASTIC CARTILAGE -

Contains network of fibers in addition to collagen fibers ~ pinna of the ear, walls of outer ear canal, epiglottis CALCIFIED CARTILAGE Calcium salts deposited within the interstitial substance of hyaline or fibrocartilage ~ jaws of sharks

not

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Site where two bones or cartilages meet Diarthrosis if freely movable, enclosed by synovial membrane; ~ hinge joints Amphiarthrosis if limited movement, no fibrocartilage; ~ joints between centra of mammalian vertebrae Synarthrosis if sutured thus immovable; ~ joints in the roof of the mammalian skull

Ankylosis -

a condition where the suture was obliterated. ~ maxilla and premaxilla of humans

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Symphysis -

V. SKELETAL REMODELING -

Bone resorption and replacement maintains homeostasis Withdrawal of calcium is regulated by parathyroid hormone and calcitonin Skeletal repair Can occur in response to mechanical stress = secondary haversian systems, thicker bones, prominences enlarged

VI. TENDONS, LIGAMENTS, AND JOINTS 1. TENDONS -

Connect muscles to bones Directly continuous with the epimysium and periosteum

2. LIGAMENTS -

Connect bone to bone Less regular arrangement of collagen

joint in the midline of the body, bilateral bones with fibrocartilage

Mineralized Tissues and the Invertebrates - matrix of collagenous fibers + carbonate Bone, dentin, vertebrates!

and enameloid

calcium

are restricted to

VII. HETEROTROPIC BONES - develop by endochondral or intramembranous - in areas subject to stress in amniotes ~ os cordis, baculum, os clitoridis, gizzard of doves, tongue of bats, gular pouch, diaphragm of camelsl syrinx of birds, upper eyelid of crocodiles; tarsal plate in humans; rostral bone in snout of swine; cloacal bone in some lizards