BIOL_315 1st Edition Lecture 6 Outline of Last Lecture I. Introduction to TissuesII. The Kinds of TissuesIII. EpitheliumIV. GlandsOutline of Current LectureI. Loose areolar connective tissue (continued)II. Dense connective tissuea. Irregularb. Regular III. Cartilage IV. Bone tissue and the bony skeletonCurrent LectureI. Loose Areolar Connective Tissue (continued)a. Loose areolar connective tissuei. Function 41. Fat Storagea. Stores energy for the body as fatb. Contains fat cells (adipose cells)i. Pick up nutrients that leave the blood and store as fatii. Extremely large, egg-shaped celliii. Cytoplasm is dominated by one large lipid dropletiv. Nucleus squeezed flat at one endb. Adipose Connective Tissuei. Adipose tissue has a lot of adipose cells ii. Built like areolar connective tissue except for its much greater abundance of fat cells iii. Just deep to skiniv. Main fat storage sit in bodyII. Dense Connective Tissuea. Function: resist exceptionally strong tension forcesi. Has much more collagenii. Fibrous b. 2 varieties i. Dense irregular connective tissue1. Resists tension from more than one directionThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.2. Example) skin – it gets pulled in every direction and continues to return to its natural state3. Denser and thicker collagen fibers than areolar connective tissuea. Oriented in more than one plane of space, often randomii. Dense regular connective tissue1. Experiences tension from a single direction only2. Main tissue in ligaments and tendons3. Lie parallel to the direction of tension4. Rows are separated by rows of fibroblast cellsa. Only cell type present  simpler than areolar or dense-irregular connective tissueIII. Cartilagea. Example) costal cartilage at the end of ribsb. Cells are separated by an abundant cellular matrixc. Chondrocytes: roundish cartilage cellsd. Contains stiff matrixi. Hollow spaces in the matrix: lacunaeii. Hollow spaces filled by chondrocytes e. Surrounded by a layer of dense connective tissue i. Pericardium: “around the cartilage”1. Retains a limited ability to repair torn or damaged cartilage when an adult, when it does it heals very poorly compared to boneii. Acts like a strong girdle and growth membrane1. Cells differentiate into chondrocytes and therefore contribute to the growth of the cartilage f. Extracellular matrix is secreted by the chondrocytes i. Consists of fibers, ground substance, and tissue fluid1. The fibers are collagen unit fibers2. Ground substance binds water, making the cartilage both stiff and springii. Contains no nerves or blood vessels1. Nutrients reach chondrocytes through diffusion from capillaries in the pericardium g. During youth it grows from both within and from without h. 3 classes, all make up some part of the skeletoni. Hyaline cartilage:1. Most abundant2. Matrix is glassy and uniform3. Many parts of skeleton first formed in hyaline cartilage , later replaced by bonea. Because can be manufactured more quickly than bone, and can keep up with rapid growth of the embryo and fetus4. Can be found:a. In the larynx, respiratory tubes, anterior end of the ribsb. Articular cartilages: spongy cushions of hyaline cartilage cover the ends of bonec. Epiphyseal plates: discs of hyaline cartilage, lie inbetween the ends and the shafts of most young bones  growth of bonesii. Elastic cartilage1. Most bendable and stretchy2. Can be found in external ear 3. Much like hyaline cartilage structure except that many elastic fibers occur in the extracellular matrix iii. Fibrocartilage 1. Most unusual type of cartilage 2. Resembles dense connective tissue in ligaments3. Found in special ligaments that are regularly pushed and pulled a. Resists both compression and tension “push me pull you”4. Example: pubic symphysis and intervertebral disks5. Lies near the attachment to the bone and grades into dense regular connective tissue on the other side 6. Consists of long thick fibers of collagen separated by row of cells i. Calcified cartilagei. When ages in the elderly ii. Extracellular matrix contains tiny crystals of calcium-phosphate salt1. Signifies the cartilage is degeneratingiii. Bone and cartilage always are distinct tissuesIV. Bone tissue and the Bony Skeletona. 5 basic functionsi. Internal framework—gives body shapeii. Levers- on which muscles pull to move your body partsiii. Protect internal organsiv. House the bone marrow—makes blood cells v. Storage sites for calcium and phosphorus b. Bone is a living tissue, much more dynamic than cartilage c. Highly active, large blood supply, and constantly being remodeledd. Bone as a connective tissuei. Bone tissue made of cells separated by an extracellular matrix1. Organic part: collagen fibers, ground substance, and tissue fluida. Bone matrix contains more collagen than most other connective tissues2. Inorganic part: tiny crystals of calcium phosphatea. Account for about 65% of weight of the bone b. Makes bone strong in resisting compression forcesc. Collagen gives it flexibility and ability to resist tension e. How a bone is built:i. Internal gross structure:1. All bones have and outer layer called compact bone2. Internal to this is the spongy bone/cancellous bone/ trabecular bone3. The bone-pieces in the network – trabeculae or spicules4. Spaces between trabeculae hold bone marrow5. Medullary cavity or marrow cavity holds bone marrow6. Outside of bone is covered by a membrane of dense connective tissue: periosteum7. Inner surface of compact bone are covered by the endosteumf. Bones and Stress: why bones have compact and spongy partsi. Bones are mostly subjected to bending forces because they are usually loaded a bit off-center and because muscles insert and pull on bones from the side1. Bending is a combination of compression and tensionii. When subjected to bending1. One side is place in compression2. The other side is in tension3. The strongest forces are at the outside a. Strong compact bone occurs here to resist 4. In the central part, compression and tension cancel each other so there is no stress in the center of a long bonea. Meaning the inside can be hollowed out i. Lightens the skeleton and provides room for bone