Bio Lecture Exam 2

What is histology defined as?

The study of tissues

What are the four primary tissue types in the human body?

Epithelial, Connective, Muscle, and Nervous (Memory: ECMN).

What are the structural characteristics of epithelial tissue?

Cells are tightly packed, little extracellular matrix, has an apical and basal surface, usually avascular, often regenerates quickly, and is supported by a basement membrane.

In epithelial tissue naming, what do the first and second parts of the name signify?

The first part indicates the number of cell layers (simple = one layer, stratified = multiple layers), and the second part indicates the shape of cells at the apical surface (squamous = flat, cuboidal = cube-shaped, columnar = tall).

What are the primary functions of simple squamous epithelium?

Diffusion and filtration.

What are the primary locations of simple squamous epithelium?

Alveoli of lungs and lining of blood vessels (endothelium).

Locations of simple cuboidal epithelium?

Kidney tubules and small gland ducts.

What is the function of simple cuboidal epithelium?

Secretion and absorption

What is the function of simple columnar epithelium

Secretion and absorption

Location of simple columnar epithelium

Much of the digestive tract.

What specialized structures may be present in simple columnar epithelium, and what are their roles?

Microvilli (increase surface area) and goblet cells (secrete mucus).

Why is pseudostratified columnar epithelium classified as a single layer?

It appears multilayered but is actually one layer because all cells contact the basement membrane.

Astrocytes

maintain chemical environment in neuron

Locations of pseudostratified columnar epithelium

Respiratory tract

What specialized structures may be present in pseudostratified columnar epithelium, and what are their roles?

Goblet cells (produce mucus) and Cilia (help move mucus)

What are the functions of stratified squamous epithelium

Protection

Location of keratinized stratified squamous epithelium

In the epidermis

Location of nonkeratinized stratified squamous epithelium

mouth, esophagus, and vagina.

What is transitional epithelium specialized for

Specialized to stretch

where is transitional epithelium found

urinary system- bladder

What are the functions of Connective Tissue

Support, Binding, Protection, Transport

What three elements are usually contained in connective tissue?

Cells, protein fibers, and ground substance.

What are the three types of connective tissue fibers and their functions?

Collagen fibers (strength), elastic fibers (stretch and recoil), and reticular fibers (supportive network).

What is areolar connective tissue

A loose connective tissue that wraps and cushions structures

Where is areolar connective tissue found

Beneath many epithelial tissues

What are the functions of adipose tissue?

Energy storage, insulation, and protection/cushioning.

Dense regular connective tissue

tendons and ligaments- run in the same direction

Dense irregular connective tissue

Found in the dermis of the skin, running in multiple directions

Why is blood classified as a connective tissue and what does it do?

It has a liquid extracellular matrix called plasma and transports substances throughout the body.

What are the characteristics of hyaline cartilage?

Most common type

Where is hyaline cartilage found

found at the ends of many bones, the nose, and the trachea.

What are the characteristics of fibrocartilage?

Strong and resistant to compression

Locations of fibrocartilage

found in intervertebral discs and the pubic symphysis.

What are the characteristics of elastic cartilage?

Flexible

Where is elastic cartilage found

found in the external ear

Connective tissue function

• protection

• framework

• binding structure

• storage

• immune protection

• transport

Elastic Fibers

Thin, branching protein fibers that stretch and recoil readily, allowing structures like blood vessels to expand and relax.

Collagen Fibers

Long, unbranched, flexible protein fibers resistant to stretching that make up $25\%$ of all protein in the human body.

Reticular Fibers

Thin, branching protein fibers that form a delicate woven framework (stroma) within organs possessing abundant space.

Cartilage

Semi-rigid connective tissue; flexible and resilient

Lacunae

Small spaces within the bone matrix that house osteocytes.

Chondroblasts

produce matrix

Chondrocytes

surround by matrix

Interstitial growth (cartilage)

Growth of cartilage from within, where chondrocytes divide and secrete new matrix, allowing the tissue to expand.

Appositional growth (cartilage)

Cartilage increases in thickness by adding new matrix layers to the surface of existing cartilage.

Function of Bone

• support and protection

• movement

• hemopoiesis

• storage of mineral and energy reserves

Hematopoiesis

The process of blood cell formation occuring in the bone marrow,

Osteoprogenitor Cells

Stem cells in the bone marrow that differentiate into osteoblasts, responsible for bone formation.

Osteoblasts

Bone-building cells that synthesize and secrete the bone matrix ("blasts build").

Osteoclasts

Large cells responsible for bone resorption and breakdown ("clasts crush").

Osteocytes

Mature bone cells situated within lacunae that maintain existing bone tissue.

Long Bones

Longer than they are wide

Epiphysis

The end of a long bone

Diaphysis

The shaft of a long bone- surrounds the hollow medullary cavity.

Metaphysis

The transitional region between the diaphysis and epiphysis that contains the growth plate in growing bones.

Periosteum

A tough outer connective tissue covering of bone containing blood vessels, nerves, and osteogenic cells. critical for bone growth, repair, and tendon/ligament attachment, but absent over articular cartilage.

Endosteum

A thin membrane that lines the internal bone surfaces. Purely metabolic

Compact Bone

solid and dense- on the external surfaces of long and flat bones

Spongy Bone

open lattice of narrow plates called trabeculae- internal surface of bones

Osteon

fundamental structural unit of compact bone

Central Canal - part of the compact bone

At the center of the osteon; carries blood vessels and nerves

Concentric Lamellae - part of compact bone

rings of bone around central canal

osteocytes- part of compact bone

housed in lacunea between concentric

Canaliculi- part of the compact bone

tiny interconnecting channels within bone that extend between lacunea- allows osteocytes to connect and communicate

perforating canals- part of compact bone

run perpendicular to and help connect multiple central canals, passageways for blood vessels and nerves.

Circumferential lamellae- part of the compact bone

surrounds the outer surface and contributes to the bone's strength and structure.

interstitial lamellae- part of the compact bone

leftover parts of osteons that have been partially reabsorbed

Ossification

formation and developement of bone

Intramembranous Ossification

Bone develops directly from mesenchymal tissue; it forms many flat bones, certain skull bones, and part of the clavicle.

Endochondral Ossification

Begins with hyaline cartilage model and produces of majority in the body

Epiphyseal Plate

large layer of hyaline cartilage at the boundary of the epiphysis and diaphysis; site for interstitial growth (5 distinct zones)

Resting Zone

Small chondrocytes in hyaline cartilage- farthest from medullar cavity and nearest epiphysis

Proliferation Zone

The growth plate zone where chondrocytes undergo rapid mitotic division on the epiphyseal side.

Hypertrophic Zone

The growth plate zone where older chondrocytes enlarge and mature.

Calcification Zone

The growth plate zone where the surrounding cartilage matrix calcifies and chondrocytes die.

Ossification Zone

The growth plate zone where osteoblasts replace the calcified cartilage framework with new bone on the diaphyseal side.

Interstitial Growth of bone

bone grows in length- occurs in the epiphyseal plate

Appositional Growth

Bone growth in width and diameter occurring in periosteum

Organic Component of Bone Matrix

The matrix fraction composed mostly of collagen fibers that provides bone with flexibility and tensile strength, preventing it from becoming brittle.

Inorganic Component of Bone Matrix

The mineral fraction composed mainly of calcium phosphate crystals that provides hardness and compression resistance, preventing excessive flexibility.

Hematoma Formation

The initial step of bone fracture repair where ruptured blood vessels produce a localized blood clot around the break site.

Soft Callus

A fibrocartilaginous bridge that forms during fracture repair to temporarily stabilize the fractured bone ends.

Hard Callus

A rigid bony collar formed during fracture repair when osteoblasts replace the fibrocartilaginous soft callus with trabecular bone.

Bone Remodeling

A continuous coupled process where osteoclasts remove older or damaged bone and osteoblasts form new bone to adapt to stress, repair microdamage, and maintain calcium balance.

Articular Cartilage function

Reduces friction and absorbs shock in moveable joints

Medullary cavity

Cylindrical space inside diaphysis- contains yellow bone marrow

Red Bone Marrow

Bone marrow responsible for producing blood cells; adult sites include the skull, vertebrae, ribs, sternum, pelvis, and proximal ends of certain long bones.

Yellow Bone Marrow

Bone marrow consisting mostly of adipose tissue that stores triglycerides and fat for energy.

Greenstick Fracture

an incomplete bone break where the bone bends and cracks on one side only without snapping into separate pieces

Part of nervous system

• neuron

• glial cells

Neuron

Excitable cells that initiate and transmit nerve impulses

glial cells

non excitable cells that support and protect neurons

astrocytes

maintain chemical environment inside neuron

Microgillia

immune system cells

Schwann cells and oligodendrocytes

helps transmit more quickly

Ependymal cells

produce spinal fluid

Dendrite

receives sensory input

Soma

the cell body of a neuron, containing the nucleus and organelles.

Axon

carries impulses away from cell body

Axon hillock

trigger zone for action potentials