Chapter 5 – Tissues (Histology) Body tissues are divided into 4 categories: Connective Nerve Muscle Epithelial

1. Connective Tissue -Functions: Connect, support, transportation (blood), defense, and storage (fat) -cells are surrounded by some type of non-living matrix -classified by their structure and the type of matrix -there are four major classes of connective tissue with subcategories

I. Fibrous, II. Bone, III. Cartilage, IV. Blood

I. Fibrous (have extracellular fibers) Loose- the stretchable fascia between organs- like an elastic glue spread between organs

Adipose- fat storage under the skin -important for protection and insulation

reticular- web like fibers of the lymphatic (immune) system - helps filter blood - contains white blood cells to destroy dangerous invaders

dense- tendons and ligaments –flexible but strong -tendon- connects muscle to bone -ligament- connects bone to bone

II. Bone bone cells are called osteocytes -osteoblast- bone building cell -osteoclast-­­ bone destroying cell the 2 cells above work together and can reshape bone a “unit” of bone is known as the Haversian System (see fig 5-20) the cells are squeezed between the hard matrix of mineral salts (mostly calcium) flat bones are called membranous bones (skull, pelvis)

Osteocytes Haversian system Cross-section of long bone

III. Cartilage chondrocytes are cartilage producing cells cartilage is avascular (no blood vessels) there are 3 subcategories of cartilage

hyaline cartilage- shiny and smooth, at the ends of bones (linings of joints) chondrocytes

Fibrocartilage- strongest and most durable, “shock absorbers” (intervertebral discs, meniscus of the knee joint)

Elastic cartilage- most flexible cartilage (ears, nose, larynx)

IV. Blood Considered a connective tissue because it is made in the bones Hematopoiesis- the process of blood production in the red marrow of the bones has a liquid matrix called plasma There are 3 main types of blood cells: Erythrocytes- red blood cells: carry O2 (some CO2) Leukocytes- white cells: kill invaders Thrombocytes- responsible for blood clotting by producing platelets

2. Muscle Tissues All are responsible for movement -May be voluntary or involuntary -May be striated or non-striated

Voluntary= may be “willed” to move Involuntary= not controlled by thought or will Striated= visible “stripes” on tissue Non-striated= no visible “stripes

I. Skeletal muscle Striated and voluntary Cells are very long and thin with multiple nuclei

II. Smooth Muscle Non-striated and involuntary Cells are shorter and each with one nucleus

III. Cardiac muscle (heart) Striated and involuntary Cells connect at dark “disks” and only one nucleus per cell.

3. Nerve Tissue -Rapidly regulate and integrate body activities -2 basic kinds of cells 1. neurons=conducting cells 2. glial cells= support cells

Important parts of a neuron: Soma: main body of cell (nucleus is here) Dendrites: short thin branches that carry signal towards the soma Axon: long thin “wire” carrying signal away from the soma Synapse: where neurons connect to transmit signal

One Very Important Glial Cell: Schwann Cells- wrap around the axon to insulate the “wiring” to speed nerve signal transmision - Responsible for the fatty white matter of the nervous system

4. Epithelial Tissue -Cells are tightly packed into sheets with no “matrix” between cells -sheets of cells attached to a “basement membrane” -cells are attached to each other by “tight junction” making a tight seal - one side is “exposed” to either internal or external environment -2 main types: membranous glandular

Membranous Epithelium Classification is based on shapes and layers:

Description of Cell Shapes: Squamous -(flat and scaly) Cuboidal -(cubic) Columnar -(tall narrow column) Pseudostratified columnar -(odd columns, not all reach the surface)

Description of Layers: Simple (one layer) Stratified (several layer of same cell type) Transitional (many layers transitioning to different cell types)

Simple Squamous - VERY thin. Where quick diffusion is necessary lining of blood vessels, tiny air sacs in lungs, parts of kidney, etc. “flat” Cross-section

Stratified Squamous - areas that receive friction skin, mouth, esophagus Cross-section

Cuboidal - lines many ducts and tubules Cross-section

Columnar epithelium - may be ciliated with tiny “hairs” (cilia) Non ciliated - lines gastrointestinal tract Ciliated - lines respiratory tract

Transitional - bladder – allows for expansion Cross-section

Glandular Epithelium Synthesizes and secretes a chemical product Endocrine gland- secrete directly to bloodstream Exocrine gland- secrete into collecting ducts Unicellular gland- single cells called goblet cells that produce mucous

Pituitary: Example of an endocrine gland

Exocrine glands come in a wide variety of shapes:

Exocrine Secretion: Merocrine- hormones released through cell membrane (sweat & salivary glands, mucous producing goblet cells) Apocrine- part of cell containing hormones pinches off (mammary gland) Holocrine- cell bursts to secrete products and must be replaced (sebaceous gland)