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Histology Notes test

Histology

The study of Tissues

Tissues are groups of cells working together

We have over 200 different types of cells

What is a Tissue?

Collection of cells and cell products and perform specific limited functions

Epithelial tissue

Epithelial covers every exposed surface of your body. Epithelial forms from the surface of the skin and line the digestive, respiratory, reproductive, and urinary tracts. In fact, they line all passageways that communicate with the outside world

Function:

Provides physical protection

control permeability - in/out

Sensation- touch, taste, sight

Produces specialized secretions-glands

Characteristics:

Has an apicalSurface-free exposed and an attached BAsal

Cellularity-Cells tightly bound together with no gaps

Avascular-No blood vessels

Regeneration

Simple Squamous

Single layer of cells that function in diffusion and absorption. Found in blood vessels and air sacs of lungs

Stratified Squamous

Several layers of cells. Layers of cells that protect from “wear and tear”. Found in the mouth, esophagus, anus and vagina and skin.

Simple Cuboidal

Single layer of cube-shaped cells, centrally located nucleus. This tissue’s main job is secretion and absorption.

Location: lines kidney tubules and small ducts of many glands

Stratified Cuboidal

Two or more layers of cuboidal shaped cells. This layer is mainly for protection is mainly for protection and limited secretions

Location : Ducts of adult sweat glands, part of the male urethra

Simple columnar

Single layer of rectangular shaped cells with nuclei near the base. often contains Goblet cells that secrete mucus. They also usually have microvilli on the apical end. Function is secretion and absorption.

Location: Lines the gastrointestinal tract (stomach and intestines)

Stratified columnar

Several layers of irregular shaped cells. Columnar cells are in the apical layer. Function is protection and secretion.

Location: Part of the Urethra, excretory ducts, and the conjunctiva of the eye

Pseudostratified columnar

Nuclei of cells at different levels. Contain cilia on the apical end. Job is to move mucus through ciliary action.

Location: Lines the airways of your respiratory system. The nasal cavity, trachea, and bronchi. These are the cells that are infected by the coronavirus.

Transitional

Appearance is variable. Its function is to allow tissues to expand and contract.

Location: Lines the urinary bladder and the uterus.

Glandular epithelium

One or more cells responsible for secreting a particular product

Secretions contain protein molecules in an aqueous (water-based) fluid

Secretion is an active process

Two major gland types develop from epithelial sheets

Endocrine glands

Ductless: Secretions (hormones) diffuse into blood vessels

Example: include thyroid, adrenals, and pituitary

Exocrine glands

Secretions empty though through ducts to zthe epithelial surface

Include sweat and oil glands, liver, and pancreas (these are both internal and external types of glands)

Connective Tissue

The Specific functions of connective tissues include the following:

Establishing a structural framework for the body

Transporting fluids and dissolved materials

Protecting delicates organs

Supporting surrounding and interconnecting other types of tissue

Storing energy, especially in the form of triglycerides

Defending the body from invading microorganisms

Classified by physical properties into:

Connective Tissue Proper

Fluid CT

Supporting CT

Connective Tissue Cells

Fibroblasts- They move around the tissue secreting the fibers and ground tissue

Macrophages- A type of white blood cell that engulfs bacteria and cellular debris

Mast cells- they respond to inflammation: the body;s reaction to injury or infections. Helps prevent blood clots

Adipocytes- Fat cells located below the skin and around the organs stores lipids used for energy

Connective Tissue Fibers

Three types of fibers are embedded in the matrix (extracellular ground substance).

Collagen Fibers- Collagen fibers are very strong and resist pulling forces. They are found in most connective tissue, especially bone, cartilage, tendons, and ligaments.

Elastic fibers- smaller in diameter, branch and join together to form a network . made up of the protein elastin. They are strong but can be stretched. They are found in the skin, blood vessels walls and kung tissue.

Reticular fibers- collagen arranged in very fine bundles that support the walls of blood vessels and form a network around the cells in some tissue. They usually form a spongy net

Connective tissue proper- loose connective tissue

The fibers are loosely intertwined with many cells

Areolar Connective tissue

Consists of fibers and several kinds of cells embedded in a semi-fluid ground substance

Function: Strength, elasticity and support

Location: Deep layers of the skin, mucus membranes, around blood vessels and nerves

Adipose tissue

Stored fats as a large centrally located droplet. Nucleus shoved into a corner of the cell

Function: Reduces heat loss, energy reserve, supports and protects

Location: Deep layer of skin, around heart and kidney, yellow bone marrow, behind your eyeball socket

Reticular connective tissue

Consists of network of interlacing reticular fibers and reticular cells

Function: Forms a supporting network for organs, binds together smooth muscle tissue cells and help filter out and remove old-red blood cells

Location: stroma of the liver, spleen, lymph nodes

Dense Connective tissue

Consists mostly of collagen fibers called fibrous or collagenous tissue

Dense regular connective tissue

The collagen fibers are parallel to each other and tightly packed

Function: provides firm attachment, helps pull muscles and reduces friction

Location: Between skeletal muscle. Tendons and ligaments

Dense irregular connective tissue

Form an interwoven meshwork with no real pattern. It supports areas that are being stressed and pulled in many directions

Function: provides strength to resist forces applied in many directions

Location: Organ capsules, covers bone and cartilage, deep dermis of the skin

Dense elastic connective tissue

Dense network of ELastic fibers with many fibroblasts in the ground substance

Function: Stretchiness and flexibility

Location:Trachea, Vocal Cords, and some artery walls

Fluid connective tissue

Distinctive cells in a fluid matrix

Blood

Lymph

Supporting connective tissue

The tissue provides a string framework that supports the rest of the body

Cartilage

contains a firm gel-like substance, fibers and Chondrocytes cells. Chondrocytes are the only cells found in cartilage

Hyaline Cartilage

The most common type of cartilage. It is tough but flexible

Function: provides stiff but flexible support

Location: Between the tips of your ribs and bones of sternum, larynx, trachea, and bronchi

Elastic Cartilage

Contains many elastic fibers that make it very flexible and resilient

Function: provides support and allows tissue to be stretched

Location: external ear and ear canal

Fibrocartilage

Has very little ground substance and is mostly collagen fibers

Function: resist compression and prevent bone-to-bone contact

Location: Pads within knees joints, between your vertebral disc

Bone

Bone has very little ground substance and is mostly hard calcium carbonate. It contains bone cells osteocytes

Compact Bone

Spongy bone