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Connective tissue:
found in all parts of the body as discrete structures or as part of various body organs.
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Functions:
protect, support (cartilage and bone), and bind together (tendons and ligaments) and other tissues of the body
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Osseous tissue:
connective tissue of the bones
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Areolar connective tissue:
soft packaging material that cushions and protects body organs
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Adipose (fat) tissue:
provides insulation of the body tissues and a source of stored food
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Hematopoietic tissue:
replenished the body’s supply of red blood cells
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What are the four main classes of adult connective tissue
- 1. Connective tissue proper- fat tissue and fibrous tissue of ligaments
- 2. Cartilage
- 3. Bone tissue
- 4. Blood
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All types of CT originate from the embryonic tissue called
mesenchyme
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Generally, connective tissue have a rich supply of
blood vessels
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Connective tissues are composed of many
cell types
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In between the cells of connective tissue are a vast amount of noncellular (non-living material), called the
extracellular matrix
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The matrix has two structural components:
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Ground substance:
- the ground substance functions as a medium through which nutrients and other dissolved substances can diffuse between the blood capillaries and cells.
- Holds the interstitial fluid
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Fibers:
- the fibers provide support. Example: collagen, fibers, elastic fibers, and reticular fibers
- All made from a single cell called the fibroblast
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Which connective tissue is the most abundant?
Areolar connective tissue
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4 basic functions of areolar connective tissue:
- Support and binding of other tissues
- Holding body fluids
- Defending the body against infections
- Storing nutrients as fat
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Collagen fibers:
- strongest and most abundant type
- Allow connective tissue to withstand tension
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Cross-linking of collagen fibers gives collagen its
strength
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Reticular fibers:
- bundles of special type of collagen
- Cluster into networks (reticulum) that cover and support all structures bordering the CT (ex. Surrounds capillaries and borders nearby epithelia)
- When pulled… these fibers glide freely past one another and “allow more give”... thus capillaries are not choked by surround reticular fibers when
- they expand
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Elastic fibers:
- long and thin
- form wide networks within the ECM
- Made up of collagen but also contain elastin, which allows them to function like rubber bands
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Ground substance:
- the part of the extracellular matrix that holds the tissue fluid (derived from the blood)
- Consists of large sugar (glycosaminoglycans) and sugar-protein molecules (proteoglycans) that soak up fluid like a sponge
- Functions as a medium through which nutrients, waste and other dissolved substances can diffuse between the blood capillaries and cells
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________ ____ is site of body’s war against infections microorganism (bacteria, viruses, fungi, and parasites)
Areolar CT
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Areolar CT contains a variety of defense cells, all of which originate as
- blood cells and migrate to the connective tissue but leaving the
- capillaries
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The following cells work to defend the body:
- Macrophages
- Plasma cells
- Mas cells
- Neutrophils, lymphocytes, eosinophils
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Areolar CT also stores energy reserves at fat
- storing cells are called fat cells (adipose or adipocytes)
- The cytoplasm of adipocytes is dominated by a single, giant lipid droplet that flattens the nucleus
- and cytoplasm at one end of the cell
- Cannot divide
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Connective tissue proper (2 subclasses):
- Loose connective tissue
- areolar connective tissue
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Loose connective tissue (more cells/less matrix)
- Areolar connective tissue
- Adipose connective tissue
- Reticular connective tissue
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Dense (fibrous) connective tissue (less cells/more matrix)
- Regular connective tissue (tendon)
- Irregular connective tissue
- Elastic connective tissue (aorta)
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Adipose connective tissue:
- 90% of mass consists of fat cells
- Highly vascularized
- Removes lipids from the bloodstream after meals and later release them into the blood as needed
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Where does adipose connective tissue occur?
In the hypodermis (layer beneath the skin) and the mesenteries (sheets if serous membranes that hold the stomach and intestines in place
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Reticular connective tissue:
Resembles areolar tissue, but the only fibers present in its matrix are reticular fibers which hold many free cells
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Where is reticular connective tissue found?
Found in the bone marrow, spleen, and lymph nodes (all have many free blood cells outside their capillaries)
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Dense regular connective tissue:
- Collagen fibers run in the same direction… parallel to the directions of pull
- Tendons and ligaments (tendons join muscle to bone and ligaments join bone to bone)
- Crowded between the fibers are rows of fibroblasts, which continuously produce the collagen fibers and scant ground substance
- Unlike areolar… poorly vascularized, no fat or defense cells
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Dense irregular connective tissue:
- Resembles areolar tissue, but the collagen fibers are much thicker.
- Collagen fibers run in different planes, allowing dense irregular CT to resist tensions from different directions
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Dense (regular) elastic connective tissue:
- In a few ligaments, bundles of elastic fibers outnumber the collagen fibers
- Example: ligamentum flavum
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Cartilage:
- a firm connective tissue resist compression (pressing) as well as tension
- Matrix: thin collagen, ground substance, lots of tissue fluid (cartilage consists of 80% water)
- A firm, flexible tissue that contains no blood vessels or nerves and just one kind of cell called a chondrocyte (contained within a cavity called a lacuna). Immune chondrocytes are called chondroblasts, which secrete the matrix during cartilage growth
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3 types of cartilage:
- Hyaline cartilage
- Fibrocartilage
- Elastic cartilage
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- Hyaline (Glassy) Cartilage
- most abundant
- forms most of embryonic skeleton
- covers ends of long bones in joint cavities
- forms costal cartilage of the ribs
- cartilage of the nose, trachea, and larynx
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- Fibrocartilage
- found in intervertebral discs
- pubic symphysis
- discs of knee joints
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- Elastic Cartilage
- support the external ear (pinna)
- epiglottis
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Bone (osseous) Tissue Characteristics:
- Calcified matrix containing many collagen fibers
- Osteoblasts (immature)- secrete collagen fibers and matrix
- Osteocytes- mature bone cells in lacunae
- Very well vascularized
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Bone (osseous) Tissue Functions:
- Supports and protects organs
- Provided levers and attachment site for muscles
- Stores calcium, fat, and minerals
- Marrow: site for blood formation
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Blood tissue:
- the fluid in the blood vessels
- The most atypical connective tissue… does not bind things together or give mechanical support
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Blood is a connective tissue for the following two reasons:
- Develops from mesenchyme
- Consists of blood cells surrounded by a nonliving matrix (plasma)
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Blood functions as a transport vehicle for the _______ ________ carrying nutrients, wastes, respiratory gases, and other substances throughout the body
cardiovascular system
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Covering and Lining Membranes, these membranes are combination of
epithelial and connective tissues
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Covers broad areas within the body… consists of
an epithelial sheet plus underlying layer of connective tissue proper
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Three types:
- Cutaneous
- Mucous
- Serous Membranes
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The cutaneous membrane is
- the skin covering the outer surface of the body
- Epithelium: the thick epidermis
- Connective tissue proper: the dense dermis
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The mucous membrane lines
- the inside of very hollow internal organ that opens outside the body
- Lines the tubes of the respiratory, digestive, reproductive, and urinary system
- All are wet and moist (many not all secrete mucus)
- All consists of an epithelial sheet directly above a layer of loose connective tissue called lamina propria
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Connective tissue underlying a mucous membrane
lamina propria
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The serous membranes are
- the slippery membranes that line the closed pleural, pericardium, and peritoneal cavities
- Produces a slippery serous fluid
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All consist of a layer of ____ _______ ______ lying on a thin layer of ____ ________ _____
- simple squamous epithelium
- areolar connective tissue
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Muscular Tissue:
Bring about most kinds of body movements
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Most muscle cells are called muscle muscle fibers because
they have an elongated shape and contract forcefully as they shorten
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Contain myofilaments, combination of
actin and myosin
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Three kinds of muscle tissue:
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Skeletal muscle:
- pulls on bones to cause body movements
- Long, large cylinders that contain many nuclei
- Appear striated due to the organization of myofilaments
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Cardiac muscle:
- occurs in the wall of the heart
- Contracts to propel blood through the blood vessels
- Like skeletal muscle.. Striated appearance
- However a)each cell has just one nucleus and b)cardiac cells branch and join at special cellular junctions called intercalated discs
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Smooth muscle:
- no visible striations in its cells
- Spindle shaped and contain one centrally located nucleus
- Found in the hollow walls of viscera (digestive and urinary organs, uterus, and blood vessels
- Acts to squeeze substance through these organs
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Nervous Tissue
The main component of the nervous organs, the brain, spinal cord, and nerves which regulate the control of body functions
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Nervous tissue contain two types of cells:
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Neurons are
- highly specialized cells that generate and conduct electrical impulses
- They have extensions that allow them to transit impulses over great distances within the body
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Supporting cells are
non conducting cells that nourish, insulate, and protect the delicate neurons
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