A&P 1: Chapter 5

Histology defintion

study of tissues

Tissues definition

group of cells and their products working together for a particular function

4 major tissue classes

Epithelial, connective, nervous, and muscular

Epithelial tissue definition

Tissue is composed of layers of closely spaced cells that cover organ surfaces, form glands, and serve for protection, sensation, and absorption

epithelial tissue location

Epidermis, inner lining of digestive tract, liver, and other glands

Connective tissue definition

Tissue with usually more matrix than cell volume; often specialized to support, bind, and protect organs

Connective tissue location

Tendons and ligaments, cartilage and bones, and blood

Nervous tissue definition

tissue containing excitable cells specialized for rapid transmission of coded information to other cells

Nervous tissue location

brain, spinal cord, nervers

Muscular tissue definition

Tissue composed of elongated, excitable muscle cells specialized for contraction

Muscular tissue location

skeletal muscles, heart, and walls of viscera

3 layers of tissue development

Ectoderm, mesoderm, and endoderm

Endoderm forms

lining of digestive and respiratory tracts and some glands

mesoderm forms

dermis, muscle, bone, and blood cells

Ectoderm forms

the nervous system, epidermis, neural crest cells

Characteristics of epithelial tissue

1. Cells closely packed with very little extracellular space
2. Specialized cell contact
3. Polarity: meaning 2 different ends
4. Avascular: no blood supply
5. High regeneration rate
6. Specializations

Gland defintion

A cell, tissue, or organ that makes and secretes a product

Endocrine gland definition

produces hormones and secretes into bloodstream via exocytosis

Exocrine gland definition

secretes product onto the body surface or into body cavities

Which glands have ducts?

exocrine

Which glands are highly vascular?

endocrine

Structural classification of exocrine glands

1. Unicellular: ex. mucous and goblet cells
2. Multicellular: consists of a duct and secretory unit

Duct type (2)

1. Simple- unbranched duct


1. compound- branched duct

Secretory Unit (3)

1. Alveolar- secretory cells form small sacs
2. Tubular- secretory cells form tubes
3. Tubuloalveolar- alveolar and tubular

How is exocrine glands classified

Based on how product is secreted

3 classifications of exocrine glands

1. Holocrine
2. Apocrine
3. Merocrine

Holocrine definition

whole membrane rupturing

Apocrine definition

membrane budding with vesicles

Merocrine definition

secrete their products by exocytosis as they are produced

Connective tissue function

1. Binds organs
2. supports the body
3. physical protection
4. immune protection
5. movement
6. Storage
7. Transport

Connective tissue characteristics

1. All CT arise from mesoderm
2. Cells widely scattered within extracellular matrix
3. Most of CT is non-living
4. Highly vascularized except for cartilage

Connective tissue components

1. Cells- fibroblasts and miscellaneous
2. Fibers- collagenous, reticular, elastic fibers
3. Ground substance

Ground substance + fibers

= matrix

Classification of CT 4 groups

1. Fibrous CT
2. Adipose tissue
3. Supportive CT
4. Fluid CT

2 types of fibrous ct

1. Loose fibrous: Areolar tissue
2. Loose fibrous: Reticular tissue

Characteristics of areolar tissue

1. produce basement membrane of epithelial tissue
2. surrounds blood vessels, nerves, esophagus, etc


1. allows blood vessels and nerves access to tissues

Characteristics of reticular tissue

1. Forms supportive network for lymphatic system and immune cells
2. Numerous leukocytes i.e. white blood cells
3. Lots of lymphocytes

Characteristics of dense regular CT

\

1. densely packed collagen fibers and slender fibroblast nuclei
2. Resists regular, predictable stress
3. Few blood cells; little ground substance

Characteristics of dense irregular CT

1. Bundles of collagen fibers but irregularly arranged
2. Few blood vessels; little ground substance

Location of dense regular CT

Tendons and ligaments

Location of dense irregular CT

Dermis, around cartilage and bone, around viscera

2 types of adipose tissue

White fat and brown fat

Characteristics of white fat

1. only fat present in adults
2. stores energy, thermal insulation, mechanical protection

Characteristics of brown fat

1. in fetuses, infants, and children
2. Brown because of abundant mitochondria


1. Generates heat

2 types of supportive CT

cartilage and bone

Characteristics of cartilage

1. Matrix is gel-like
2. Avascular
3. Chrondoblasts secrete matrix
4. Chrondoblasts mature into chrondocytes
5. Can withstand tension and compression

3 types of cartilage

Hyaline, elastic, fibrocartilage

Characteristics of hyaline

1. Ease joint movement
2. move vocal chords
3. growth zones of long bones

Characteristics of elastic

1. Flexible support
2. external ear

Characteristics of fibrocartilage

1. Absorbs shock

Characteristics of Bone

1. osseous tissue
2. Osteoblasts, osteoclasts, osteocytes
3. FlMineralized matrix

Characteristics of Blood

1. Plasma is the matrix
2. Red blood cells and white blood cells

Nervous tissue includes 2 cells

neurons and neuroglia/glial cells

Muscular tissue function

specialized to convert chemical energy (ATP) into mechanical energy (movement)

3 types of muscular tissue

skeletal, cardiac, and smooth

Characteristics of skeletal muscle

1. most are attached to the bone
2. Used in body movement
3. voluntary muscle movement
4. Nonbrancing; have striations

Characteristics of cardiac muscle

1. Only found in the heart
2. pumps blood
3. branching; have striations and intercalated discs

Characteristics of smooth muscle

1. found in walls of blood vessels and digestive tract
2. controls blood pressure and moves food through digestive tract
3. Involuntary movements
4. No striations

Most cells are connected by

cellular junctions

What do cellular junctions do?

1. Holds cells together
2. Controls the movement of substance between cells
3. Allow tissues to resist stress
4. Allow cells to communicate with each other

3 types of specialized junctions

1. Tight junctions
2. Desmosomes
3. Gap junctions

Tight junction function

Prevents materials from passing between cells

Desmosomes function

resists mechanical stress but allows materials to move between cells

Gap junction function

Allows materials to pass between cells

Unipotent definition

can only make one type of cell

Multipotent definition

can make a few types of cells

Pluripotent definition

can make any type of cell in your body

2 main mechanisms for tissue repair

Regeneration and fibrosis

Regeneration definition

Replacement of damaged cells with cells of the same type

Fibrosis definition

“Fills the gaps” with scar tissue (Fibrous CT)

Atrophy definition

shrinking of a tissue due to loss of cell and cell size

Necrosis definition

Premature, pathological tissue death due to trauma, toxins, infection, etc

Infarction definition

Sudden death of tissue due to lack of blood supply

Gangrene definition

Necrosis of tissue due to lack of blood supply

Apoptosis definition

programmed cell death