Retrieval of fibers from victims should ideally be done

fibers are still present weeks later

Primary transfer of fibers to a victim occur when

the suspect directly transfers the fibers to the victim

when they come from a primary source like a sheep or cotton plant

when a suspect attempts to change the fibers to be less conspicious

when the victim first buys a piece of clothing

Which of these indicates why the shape of a fiber is important in a criminal investigation?

Some shapes of fiber are only made a short time

Color values may change depending on when the fiber was manufactured

Some fibers are manufacturer specific

The greater number of fibers found on a victim indicates

The more likely some confrontation happened between the victim and the perpetrator

the cheapness of the coloring of the fabric

the shorter the fibers were on the perpetrator's clothes

the breakage rate of the fibers

White cotton and blue denim are often less important in a case because

they are relatively inexpensive

A case using fibers for evidence must present

how rare the coincidence is that the fiber would be on the victim otherwise

how easily this fiber takes the dye present on the clothing

how frequently this fiber is made into clothing

Fibers and Forensics

COVERINGS OF BONE SURFACE Periosteum: Outer layer of Type I collagen fibers and fibroblasts Sharpey’s (perforating) fibers penetrate the bone matrix and bind periosteum to bone Inner layer of osteoprogenitor cells and osteoblasts Functions: Provide nutrition for osseous tissue Supply osteoblasts for repair or appositional bone growth Endosteum - lines internal cavities (and trabeculae) within bone 1 layer of flat osteoprogenitor cells, osteoblasts, and some connective tissue

Secondary (Lamellar) Collagen fibers are highly organized and arranged in lamellae (layers) of calcified matrix Lamellae surrounding a canal containing a nerve, vessels, and loose connective tissue is a Lamellae surrounding a canal containing a nerve, vessels, and loose connective tissue is a Haversian system (osteon) Between or within lamellae are lacunae 80% is compact and 20% is spongy

Integumentary system: skin and its accessory structures such as hair, sebaceous glands, sweat glands and nails. Antigen presenting cells (APCs)- a heterogeneous group of immune cells that mediate the cellular immune response by processing and presenting antigens for recognition by certain lymphocytes such as T cells. Classical APCs include dendritic cells, macrophages, Langerhans cells (macrophages of the skin that can migrate to the lymph vessels) and B cells. Hemidesmosomes- multiprotein complexes that facilitate the stable adhesion of basal epithelial cells to the underlying basement membrane. Type I collagen- fibrils form fibers which can form bundles; resists tension (most abundant; in tendons, bones, dermis) Type VII collagen- collagen type essential in strengthening and stabilizing the skin.

The cytoskeleton is a network of thin tubes and filaments that crisscrosses the cytosol. The tubes and filaments give shape to the cell from the inside in the same way that tent poles support the shape of a tent. The cytoskeleton also acts as a system of internal tracks, shown in Figure 4-18, on which items move around inside the cell. The cytoskeleton’s functions are based on several struc- tural elements. Three of these are microtubules, microfilaments, and intermediate filaments, shown and described in Table 4-2. Microtubules Microtubules are hollow tubes made of a protein called tubulin. Each tubulin molecule consists of two slightly different subunits. Microtubules radiate outward from a central point called the centrosome near the nucleus. Microtubules hold organelles in place, maintain a cell’s shape, and act as tracks that guide organelles and molecules as they move within the cell. Microfilaments Finer than microtubules, microfilaments are long threads of the beadlike protein actin and are linked end to end and wrapped around each other like two strands of a rope. Microfilaments con- tribute to cell movement, including the crawling of white blood cells and the contraction of muscle cells. Intermediate Filaments Intermediate filaments are rods that anchor the nucleus and some other organelles to their places in the cell. They maintain the inter- nal shape of the nucleus. Hair-follicle cells produce large quantities of intermediate filament proteins. These proteins make up most of the hair shaft. 84 CHAPTER 4 TABLE 4-2 The Structure of the Cytoskeleton Property Microtubules Microfilaments Intermediate filaments Structure hollow tubes made of two strands of intertwined protein fibers coiled into coiled protein protein cables Protein subunits tubulin, with two subunits: å actin one of several types of and ∫ tubulin fibrous proteins Main function maintenance of cell shape; cell maintenance and changing of maintenance of cell shape; motility (in cilia and flagella); cell shape; muscle contraction; anchor nucleus and other chromosome movement; movement of cytoplasm; cell organelles; maintenance of organelle movement motility; cell division shape of nucleus Shape Microtubules provide a path for organelles and molecules as they move throughout the cell. FIGURE 4-18 Microtubules Nucleus Endoplasmic reticulum Mitochondrion Ribosomes Copyright © by Holt, Rinehart and Winston. All rights reserved. Copyright © by Holt, Rinehart and Winston. All rights reserved. CELL STRUCTURE AND FUNCTION 85 1. Explain how the fluid mosaic model describes the plasma membrane. 2. List three cellular functions that occur in the nucleus. 3. Describe the organelles that are found in a eukaryotic cell. 4. Identify two characteristics that make mitochon- dria different from other organelles. 5. Contrast three types of cytoskeletal fibers. CRITICAL THINKING 6. Relating Concepts If a cell has a high energy requirement, would you expect the cell to have many mitochondria or few mitochondria? Why? 7. Analyzing Information How do scientists think that mitochondria originated? Why? 8. Analyzing Statements It is not completely accurate to say that organelles are floating freely in the cytosol. Why not? SECTION 3 REVIEW During cell division, centrioles organize microtubules that pull the chromosomes (orange) apart. The centrioles are at the center of rays of microtubules, which have been stained green with a fluorescent dye. FIGURE 4-20 Cilia and Flagella Cilia (SIL-ee-uh) and flagella (fluh-JEL-uh) are hairlike structures that extend from the surface of the cell, where they assist in movement. Cilia are short and are present in large numbers on certain cells, whereas flagella are longer and are far less numerous on the cells where they occur. Cilia and flagella have a membrane on their outer surface and an internal structure of nine pairs of micro- tubules around two central tubules, as Figure 4-19 shows. Cilia on cells in the inner ear vibrate and help detect sound. Cilia cover the surfaces of many protists and “row” the protists through water like thousands of oars. On other protists, cilia sweep water and food particles into a mouthlike opening. Many kinds of protists use flagella to propel themselves, as do human sperm cells. Centrioles Centrioles consist of two short cylinders of microtubules at right angles to each other and are situated in the cytoplasm near the nuclear envelope. Centrioles occur in animal cells, where they organize the microtubules of the cytoskeleton during cell division, as shown in Figure 4-20. Plant cells lack centrioles. Basal bodies have the same structure that centrioles do. Basal bodies are found at the base of cilia and flagella and appear to organize the devel- opment of cilia and flagella.

Nucleus pulposus • Located in the mid-to-posterior part of the disc. • Pulplike gel or Hydrophilic like gel consistency large branching proteoglycans. • Collagen forms an infrastructure that support the proteoglycan network. • Hydrated proteoglycans are thin type II collagen fibers, elastin fibers, and other proteins • Proteoglycan is water-binding glycosaminoglycans linked to core proteins • In youth the nucleus pulposus within the lumbar discs consists of 70% to 90% water. • The hydrated nucleus allows the disc to function as a hydraulic shock absorption system, dissipating and transferring loads across vertebrae

BONE MATRIX (OSTEOID) Inorganic matter Calcium, phosphorus, bicarbonate, magnesium, etc. Calcium and phosphorus form hydroxyapatite crystals Organic matter Type I collagen (90%) Ground substance of proteoglycan aggregates and multiadhesive glycoproteins (e.g., osteonectin) Mixture of minerals with collagen fibers (i.e., hydroxyapatite crystals are deposited in the gap regions along the collagen fibers) produces the hardness and resistance of bone.

1. SA node sends an impulse causing the atria to contract 2. Blood moves from the right atrium into the right ventricle past the tricuspid valve 3. Blood moves from the left atrium into the left ventricle past the mitral or bicuspid valve 4. Impulse pauses at AV node to allow for maximum blood to be squeezed into the ventricles 5. Impulse travels to the AV bundle (or bundle of His) and down the bundle branches 6. Impulse travels out Purkinje fibers causing the apex to contract 7. The apex contraction increases the blood pressure in the ventricles causing the Mitral and Tricuspid (AV) valves to close. 8. Atria repolarize and begin to fill 9. Purkinje fibers cause the ventricle walls and papillary muscles to depolarize (contract) 10. Papillary muscles hold the AV valves shut (keep them from prolapsing) through the chordae tendineae connection 11. The aortic and pulmonary semilunar valves open when the pressure is higher in the ventricles than in the major arteries 12. Blood moves from right ventricle to pulmonary trunk/arteries past the pulmonary semilunar valve 13. Blood moves from left ventricle to aorta past the aortic semilunar valve 14. Blood pathway is arteries to arterioles, to capillaries (or capillary bed), to venules, veins and vena cava back to the right atrium 15. The ventricles start to repolarize (relax) which decreases the pressure in the ventricles 16. When the pressure is lower in the ventricles than in the major arteries, blood moves back toward heart shutting semilunar valves 17. When the aortic valve closes, the openings to the coronary arteries are exposed 18. Back pressure in the aorta pushes blood out the left and right coronary arteries supplying the heart with oxygenated blood 19. The AV valves open and blood moves from the atria into the ventricles when the ventricular pressure falls below atrial pressure. 20. The process starts again when the SA node fires causing the atria to contract.

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