Histology

The study of tissues within body organs

1. Connective Tissue FUNCTION – protects and supports the body and its organs Binds organs together Stores energy reserves as fat Help provide immunity to disease-causing organisms Fills space Provides support, protection, framework Helps repair tissue

Types of C.T. cells Mast cells – prevent clots Macrophages – consumers Fibroblasts – produce fibers – Collagen: bones, ligaments, tendons – Elastic: respiratory

Fibroblasts

Main Types of Fibers Collagenous fibers – strong and flexible (bones, tendons, ligaments) Elastic fibers – very flexible (ears and vocal cords)

Main Categories of C. T.

Loose C. T. or Areolar tissue Found underneath dermis Surrounds blood vessels Empty spaces

Adipose tissue (fat)

Fibrous C. T. Ligaments – bone to bone Tendons – muscle to bone

Hyaline Cartilage Covers end of nose, joints, and respiratory passages

Elastic cartilage External ear and larynx

Fibrocartilage

Osteocytes (Compact Bone)

Blood Tissue

#2 Muscle Tissue FUNCTION – generates the physical force needed to make body structures move

Cardiac Muscle

Smooth Muscle

Skeletal Muscle

#3 Nervous Tissue FUNCTION – detects changes in a variety of conditions inside and outside the body – Responds by generating action potentials that help maintain homeostasis

Nervous Tissue (spinal cord)

Multipolar Motor Neuron

#4 Epithelial Tissue FUNCTION – Covers body surfaces (inside and out) – Lines hollow organs, body cavities, and ducts – Forms glands Characteristics – Attaches to basement membrane – Usually has no blood supply – Cells divide rapidly – Cells tightly packed together

Epithelium Epithelial tissue functions to: – Protect surfaces (skin) – Secrete material (glands) – Absorb material (intestines) Consists of cells that line body surfaces, both internal (lining of gut) and external (skin) Epithelium lines the mouth, esophagus, uterus and vagina, ducts of the pancreas and liver, blood vessels (called endothelium), urethra and ureters, tubules of the kidney, air sacs (alveoli) of the lungs and many other sites.

Classification Classified and named according to – Shape of outermost cell layer Squamous – flat Cuboidal - square Columnar - rectangular Transitional – Whether or not tissue is one layer thick (simple) or has multiple (stratified)layers – Whether or not the cells are ciliated or secrete mucous

Simple Squamous Air sacs in lungs Walls of capillaries Function: allow diffusion

Simple Cuboidal Epithelium Function: secretion and absorption Found in kidney tubules, ducts, and ovaries

Simple Cuboidal Cross sections – cube shaped cells line edge of ducts The white spaces are lumen (opening/duct) and would normally be filled with fluid

Simple Cuboidal Many tubules are seen in this kidney cross section The cells have a cube shape and surround the empty white lumens

Simple Columnar Function: secretion and absorption Found in digestive tract and uterus Contain goblet cells to secrete mucus Can have microvilli

Transitional Epithelium Cells that are flattened and cuboidal Usually found in the bladder Has the ability to stretch Blocks diffusion

Ciliated Pseudostratified Columnar Epithelium Goblet cells produce mucus Same as columnar except has different nuclear layers (some in center, some near edge) Found in lining of passages and reproductive system

Stratified Squamous Epithelium Mouth and skin Cells are scale- like Function – protect from abrasions

Keratizined Strataified Squamous Skin Outer layers of cells are filled with keratin – Protein for waterproofing Dead cells, no nucleus

Stratified Cuboidal Sweat gland ducts Only two layers of cells Found in the dermis

Stratified Columnar Rare Found in the largest ducts of salivary glands Basal (bottom) layers are cuboidal and top (apical) layer is columnar Large droplets are mucus in Goblet cells

A – basement membrane B – simple squamous C – simple cuboidal D – simple columnar E – pseudostratifi ed columnar F – stratified squamous G – stratified columnar H – stratified cuboidal I – transitional

Key for Histology Single layer or more than 1 layer? (simple, stratified) Shape – square, rectangle, mix, flat? (cuboidal, columnar, squamous, transitional) Look closely to determine if pseudo-