Tissues Tissues A collection of cells with a common function Four basic tissues 1. Epithelial 2. Connective 3. Muscular 4. Nervous
Epithelia: cells in layers Types of epithelia 1) lining Layers of cells which line ducts and cavities 2) glandular* more on this in A&P II Collections of cells found within glands. Two types of glands. a) exocrine glands Secrete their into ducts; lead to the body surface and cavities Example: sweat and sebaceous glands b) endocrine glands Secrete into the blood or interstitial spaces (between cells.) Ductless glands Form the endocrine system
layers of epithelial cells One to many layers 1) simple Single layer 2) stratified Many stacked, layers 3) pseudostratified Single layer; looks like many cell shapes Variety of spaces; most common 1) squamous Flat, disc shaped cells
cell shapes 2) cuboidal Cube shaped cells; as tall as wide cell shapes 3) columnar Cylindrical shaped cells Taller than wide
cell shapes 4) transitional! Change shape; squamous to dome shaped and back. Lines structures where the volume changes occurs; urinary bladder Epithelia I) simple squamous!! Function: rapid diffusion; lungs. lines blood vessels; peritoneum; parts of kidneys.
Epithelia II) simple cuboidal Function: Slower diffusion. Processing and modification of the diffusing substance. Tubules of the kidneys. Epithelia III) simple columnar Function: Active transport and modification of materials. Lumen of the digestive tract to the blood.
Epithelia IV) stratified squamous!! Function: Protects against abrasion 1) nonkeratinized- mucous or wet! Location: oral cavity, rectum, vagina. Moist- lots of mucus for lubrication. 2) keratinized or dry- skin!!! Superficial layers are dead and squamous Filled with keratin; protein Acts as barrier to water and infection. Epithelia V) transitional- bladder! Layer can stretch with increase in urine volume
Epithelia VI) pseudostratified- respiratory All the cells begin on the basal side, few reach the surface; Ciliated. Respiratory tract- trachea, bronchial tubes, etc. Connective tissue (CT)! Function: to bind tissues together. Components: fibers, ground substance and cells 1)Fibers! Proteins provides strength Fibroblasts!! Cells that make fibers; also produce ground substance Collagen other types!! Very common in CT. Elastic fibers- stretchy. Reticular- forms a mesh.
2) Ground substance Medium in which fibers and cells are held. extracellular matrix= fibers + ground substance. Hyaluronic acid or HA Soft, flexible material; fresh Jello Large amounts in loose CT; smaller in dense CT Chondroitin sulfate More stiff, dryer; several day old Jello Cartilage.! Hydroxyapatite!! Very hard; rock-like. Bone. 3) Cells! Living component; makes fibers and the ground substance Fibroblast Cells that make collagen and elastic fibers Chondrocytes! Chondro= cartilage; cyte= cells; Cartilage cells Cells that make cartilage; chondroitin sulfate and fibers osteoblasts! Osteo= bone
Adult Fibers Ground substance Loose areolar Collagen-low fiber content Hyaluronic acid (HA) lots Cell type Fibroblasts Example Under the skin & other tissues Dense irregular Dense regular Collagen-high Random pattern Collagen-high parallel pattern HA less Fibroblasts Fasciae, periosteum perichondrium HA less Fibroblasts Ligaments and tendons Fasciae- sheets of CT fibers; between/under organs. Periosteum- sheet of fibrous CT; covers bones. Perichondrium- sheet of fibrous CT; covers cartilage. Adult Adipose Fibers Collagen-low fiber content HA low Ground substance Cell type Example Adipocytes lots Subcutaneous fat Reticular Reticularforms a mesh HA- moderate and varies Reticulocytes Liver, spleen and lymphatic Elastic Elasticstretchy HA- moderate Fibroblasts Elastic tissue of the lungs
Cartilage Hyaline Fibrous Fibers Collagen-low fiber content Ground substance Cell type Example Chondroitin Sulfate (CS) lots Chondrocytes in lacunae Collagen-high CS low Chondrocytes Ends of bones, tracheal rings, costal cartilage Intervertebral discs Meniscus of knee, pubic symphysis Elastic Elastic-high CS low Chondrocytes Pinna of the ear (external) Lacunae: a space within the matrix of CT Bone- osseous Connective tissue Fibers; collagen Osteocytes Cells of osseous tissue Make collagen and hydroxyapatite - hard ground substance Haversian system System of channels, spaces and cells. Next chapter
Membranes Comprised of... Epithelial membranes consist of 1-epithelium + For example squamous, columnar, etc. 2-basement membrane + A glue-like layer secreted by the epithelial cells. Binds the epithelium to the CT layer underneath 3-connective tissue! Such as loose areolar CT under the skin mucous membranes Secrete mucus. Columnar layer with goblet cells. Produce mucus Moisten and lubricate the epithelium. Examples: Mucus membranes of the digestive system.
serous membranes Produce serous fluid Protect and lubricate surfaces. Examples: serous membranes of pleural spaces pericardial space peritoneal space