Chapter 5 Notes: Histology
Histology - “study of tissues”
Tissue: group of similar cells that perform a common function for body homeostasis. Intercellular junctions and/or matrix hold the cells together, if held together at all. (matrix of blood is plasma)
Matrix: nonliving material (protein, minerals, salts, etc.) that surrounds the cells of tissues.
Principle Tissue Types
1. Epithelial
2. Connective
3. Muscular
4. Nervous
Primary Germ Layers - fetus formation begins with three germ layers that develop into organs, etc. (histogenesis)
Endoderm (epithelial) Mesoderm (epithelial, muscle, Ectoderm (epithelial, nervous)
connective)
Digestive & respiratory epithelium Muscles Epidermis
Urethra epithelium Skeleton (bones & cartilage) Lining of mouth, anus, nostrils
Bladder Blood Sweat & sebaceous glands
Liver and pancreas Blood vessel epithelium Hair
Dermis Brain & spinal cord
Excretory & reproductive organs Eyes, nose, ear epithelium
Tissue Group #1: Epithelial Tissue (epithelium): most widespread throughout the body with limited matrix (interstitial fluid), that appears as a continuous sheet under the microscope.
1. Functions
a. Protection: skin, surrounds organs and lines body cavities, protection from chemical and mechanical injury and pathogens
b. Sensory functions: receptors in skin, nose, eyes, ears, etc.
c. Secretion: products include hormones (pancreas and pituitary), mucus, digestive enzymes, etc.
d. Absorption: lining tissue of gut and respiratory tract
e. Excretion: lining of kidneys
2. Generalizations: cells attach to an underlying layer of connective tissue by a thin, noncellular (glycoprotein and connective fibers), adhesive, permeable material called a basement membrane that the cells make themselves
a. Avascular - no blood vessels (oxygen and nutrients diffuse through basement membrane)
b. Cells joined by desmosomes and tight junctions and reproduce through mitosis
3. Classification
a. Membranous - covering/lining
1. Layer Type
a. Simple - one layer
b. Stratified - multiple layers of cells
c. Pseudostratified (“false layers”) - single layer that looks like two layers
1. ciliated - found in respiratory tract
2. non-ciliated - male urethra
d. Transitional - multiple layers of epithelial cells; “hodge-podge” (100+ layers)
1. found in urinary tract
2. can look cuboidal until bladder stretches, then looks squamous
2. Shape Type
a. Squamous – circular, flat, plate-like (scales)
b. Cuboidal – square, more cytoplasm than squamous
c. Columnar – rectangular, higher than wide, narrow, cylindrical
Types of Membranous Epithelium:
1. Simple Squamous Epi.: alveoli of lungs, lining of blood and lymph vessels, pleura, pericardium, and peritoneum and covering all organs.
2. Simple Columnar Epi.: surface of mucous (water, electrolytes, and glycoproteins) membranes of stomach, intestines, uterus, uterine tubes, and lining of parts of respiratory tract. Many have goblet cells (mucous production) , microvilli, cilia.

3. Simple Cuboidal Epi.: glands and ducts (kidneys)
4. Pseudostratified Columnar Epi.: line air passages of respiratory tract and parts of male reproductive system (urethra).
-cells of differing heights (not all reach surface)
- mucous secretory goblet cells and cilia present
5. Stratified Epi.:
1A) Stratified Squamous Epi.: multiple layers of flattened squamous cells on
outer surface of skin
(Keratinized cells (protein) to contribute to protective quality of skin)
1B) Non-keratinized Stratified Squamous Epi.: lining of vagina, mouth,
esophagus (moist, internal cells so no tough keratin needed)
2) Stratified Cuboidal Epi.: sweat gland ducts, lining of pharynx, covering
of epiglottis
3) Stratified Columnar Epi.: segments of male urethra and mucous layer of
anus
4) Stratified Transitional Epi.: wall of urinary bladder, uterus, and other places subject to stress and tension changes. As bladder fills, cells change from cuboidal to squamous and protects from tearing.
b. Glandular Epithelium- secrete products (modified epithelial tissue)
Types of Glandular Epithelium:
1. Endocrine glands - secrete into blood, ductless (pituitary, thyroid)
2. Exocrine glands - secrete into ducts (salivary glands)
a. Apocrine - accumulate their secretory product at the apical (tip) surface of each cell, which then separates from the remainder of the gland. The cells then repair themselves.
Ex: Mammary gland
b. Holocrine - entire cell and its secretions
accumulate as the gland's secretory product
; cell ruptures to release products
Ex: sebaceous (oil) glands of skin (lubricates)
c. Merocrine – discharges secretions directly through the cell plasma membrane and cell stays in tact
Ex. salivary and sweat glands
Tissue Group #2: Connective Tissue: around or near every organ,
many varied forms (bones to blood!)
1. Functions
a. Structural support: tendons, ligments, cartilage, bones
b. Metabolic components: blood transporting oxygen, carbon dioxide, and glucose
c. Blood components:
d. Defense: barriers to bacteria (ex. Macrophages in areolar connective tissue)
2. Generalizations
a. Matrix - intracellular material: mostly matrix with few cells (fibroblasts, macrophages, mast cells)
b. Ground Substance - cells, fibers, fluid all embedded in matrix
c. Matrix is composed mostly of structural proteins
3. Classification
a. (Types of) Fibrous Connective Tissue: “stretchable, elastic-like glue”
1. Loose connective tissue (areolar): cells are called fibroblasts
a. surrounds blood vessels and nerves
b. pliable, mesh-like tissue with a fluid matrix
c. functions to cushion and protect body organs (between other tissues and organs)
d. 3 types of fibers (VERY fibery matrix)
1. Collagenous fibers - collagenous fibers are made of collagen and consist of
bundles of fibrils that are coils of collagen molecules (under epithelium of skin)
2. Elastic fibers - elastic fibers are made of elastin and are "stretchable." (cartilage of ear)
3. Reticular fibers - reticular fibers consist of one or more types of very thin collagen fibers. They join connective tissues to other tissues (connects capillaries to cells and nerves within other tissues)
2. Adipose tissue (“fatty tissue”)
a. stores energy in the form of fat under skin
b. cushions and insulates the body (see page 137 for male vs. female fat areas)
c. each adipose cell contains a droplet of fat in a storage vesicle that pushes the organelles to the edge of the cell
3. Reticular tissue
a. The fibers form a soft skeleton (stroma) to support the lymphoid organs (spleen, lymph nodes, etc.) to filter blood
b. Holds together adipose tissue
c. Filters harmful substances out of blood (phagocytes in this tissue)
4. Dense fibrous tissue
a. Regular
1. provides strong connection between different tissues
2. The collagen fibers are bundled in a parallel fashion.
3. Tendons (anchors muscle to bone) and ligaments (connect bone to bone)
b. Irregular
1. not parallel fibers
2. mostly in dermis ( inner) layer of skin to withstand stress of stretch and also makes scars
b. Bone Tissue / Osseous Tissue: highly specialized connective tissue
1. major structural and supportive connective tissue of the body
2. forms the rigid part of the bone organs that make up the skeletal system
a. Osteon (Haversion System) - primary anatomical and functional unit of mammalian compact bone

3. Bone has a unique matrix of organic collagen and
mineral salts: 65% of bone is matrix and is responsible
for hardness of bone. Matrix is embedded with:
- Osteoblasts: bone forming cells
- Osteocytes: mature bone cells (osteoblasts become
osteocytes)
Osteoclasts: bone eroding cells that dissolve bone away from osteocytes and they can then resume making bone again as osteoblasts

***Osteocytes become trapped in hard bone and cease making new bone
.
***Osteoclasts dissolve bone away from osteocytes and they begin making new bone cells.

4. Central Haversian Canal: provides bone cells with nutrient blood and nerve cells


Ossification (osteogenesis): when cartilage matrix calcifies and the chondrocyte cells can no longer get oxygen and nutrients by diffusion and the cells die, being replaced by living bone that has osteocyte/osteoblast
cells that can remain alive due to the canaliculi.
5. Functions of bone:
a. Support (attachment) for muscles, organs, and soft tissues.
b. Leverage and movement
c. Protection of vital organs (ribs, etc.)
d. Calcium phosphate storage (mineral storage for body)
e. Hematopoiesis - formation of blood cells in marrow of long bones
c. Cartilage: cushioning, support, and “slipability”
one cell type (chondrocyte); avascular therefore nutrients reach cell by diffusion therefore cartilage injuries heal slowly due to lack of nutrients.
During embryo development, most cartilage produced in body ossifies into bone.
1. Hyaline cartilage
a. exists on the ventral ends of ribs; in the larynx, trachea, and bronchi; and on the articular surface of bones at joints
b. slimy mass of a firm consistency, but of considerable elasticity
c. contains no nerves or blood vessels
d. transluscent
e. lots of collagen
2. Fibrocartilage (also called articular cartilage) for cushioning and slipability
a. found in the pubic symphysis (major joints of pubic bones), intervertebral discs (between vertebra), meniscus (curved pads of knee)
b. looks like dense regular connective tissue, but may be distinguished from them by being surrounded by a concentrically striated area of cartilage matrix, their lacunae, and by being less flattened.
c. strongest/most durable (shock absorbers)
d. lots of collagen
3. Elastic cartilage (not much collagen)
a. present in the outer ear, larynx, and epiglottis
b. Elastic fibers stain dark
c. Very flexible

Perichondrium
a. surrounds cartilage
b. specialized membrane with blood vessels from which diffusion occurs

d. Blood (hematopoietic connective tissue) - transports nutrients, gases, and wastes; maintains temperature and pH homeostasis
- Blood tissue is formed in red bone marrow.
- Plasma plus the blood cells is called whole blood.
1. plasma (fluid of blood)
a. yellow liquid component of blood
b. 55% of the total blood volume
c. mostly water (92% by volume), dissolved proteins, glucose, clotting factors, mineral ions, hormones and carbon dioxide
2. cells - 45% of blood
a. erythrocytes (“red cell”)
1. most common type of blood cell
2. coated with protein hemoglobin and principle means of distributing O2
b. leukocytes (“white cell”)
1. defends the body against both infectious disease (macrophages, mast cells, killer T cells, helper T cells, phagocytes)
c. thrombocytes (platelets)
1. main purpose is for blood clotting
Tissue Group #3: Muscle Tissue
1. Functions
a. Produce force (contractions!)Ex. Heart PUMPS blood, Esophagus moves food by peristalsis.
b. Causes motion (movement)
2. Generalizations
a. Bundles of microfilaments (protein fibers) that give muscles the ability to shorten or contract more so than any other tissues

3. Classification
a. Skeletal muscle tissue (also called striated voluntary)
1. muscle attached to bone by tendons (regular, dense fibrous connective tissue)
2. striated (stripes under microscope)
3. voluntary
4. can have more than one nuclei
5. long, narrow thread-like shape to tissue

b. Smooth muscle tissue (also called visceral muscle tissue)
1. viscera of hollow internal organs (stomach, intestines, blood vessels, esophagus)
2. nonstriated
3. involuntary
4. peristalsis allows you to eat standing on your head
c. Cardiac muscle tissue
1. wall of heart
2. striated
3. involuntary
4. unique dark bands where membranes of cells are joined by tight junctions called intercalated discs
5. cells are called myocardiocytes
Tissue Group #4: Nervous Tissue
1. Function
a. Rapid regulation (homeostatic control)
2. Generalizations
a. More developed excitability and conductivity than any other tissue type (for communication)
b. Organs - brain, spinal cord, neurons (cells)
3. Classification
a. Neurons - nerve cell for conduction of impulses
1. soma - cell body (organelles)
2. axon - conducts impulses away from soma
3. dendrites - carry signal towards soma
b. Nervous tissue runs through all other tissue supported by: Neuroglia - special connecting/supporting cells that are the matrix of nervous tissue
Tissue Repair (regeneration)
1. Epithelial and connective tissue
a. best regeneration
2. Muscle tissue
a. limited regeneration
b. replaced with connective tissue instead of muscle tissue, therefore some function is lost
3. Nerve tissue
a. limited to no regeneration
b. brain or spinal cord permanent damage
c. discovery of nerve growth factors is aiding in regenerating tissue
Body Membranes
A. Epithelial membranes
1. Cutaneous membranes - skin
2. Serous membranes - line body cavities and organ surface
a. visceral - line organ
b. parietal - line cavity
3. Mucous membranes - line body surfaces open to exterior (respiratory, urinary, reproductive)
4. Synovial membranes – line spaces between bones at joint and secrete synovial fluid to reduce friction

Mechanisms of Disease: Tumors and Cancer
A. Neoplasms (tumors)
1. Benign tumors
2. Malignant tumors (cancers)
B. Causes of cancer (malignant tumors)
1. Genetic factors
2. Carcinogens
3. Age
C. Detection and treatment of cancer
1. Detection
a. Self-examination
b. Medical imaging
c. Blood tests
d. Biopsy
2. Treatment
a. Chemotherapy
b. Radiation therapy
c. Laser therapy
d. Immunotherapy