HISTEM W2 Basic Tissues

What are the 3 embryological cell layers in which basic tissues develop from?

1. Ectoderm

2. Mesoderm

3. Endoderm

What type of epithelial tissue is derived from the ectoderm?

Skin and oral mucosa

What type of epithelial tissue is derived from endoderm?

Respiratory and digestive tract epithelium

What type of epithelial tissue is derived from mesoderm?

Urinary tract

Describe the different epithelial cell arrangements: Simple, Stratified, Pseudo stratified

Simple - single layer

Stratified - 2 or more layers

Pseudostratified - 1 layer but looks like 2

Describe the different epithelial cell shapes: Squamous, cuboidal, columnar, transitional

Squamous - flat

Cuboidal - cube

Columnar - rectangular/column shaped

Transitional - changes shape

Describe the 2 epithelial cell functions:

Keratin - dead layer, no nucleus

Ciliated - hair-like projections (propel other substances)

Describe simple squamous epithelium. Where can it be found?

• Very thin, flat cells that may vary in shape.

• Covers connective tissue with little ECM

• Performs filtering function on moist surfaces

• Endothelium - single cell lining vessels and serous cavities

Location:

• Pulmonary alveoli

• Inner and middle ear

• Blood and lymphatic vessels

• Heart

• Serous cavities

Describe simple cuboidal epithelium. Where can it be found?

• cube-like, nucleated cell

• fx: protection/covering for organs, contributes to secretion

Location:

• Lines the ducts of various glands such as salivary glands

Describe simple columnar epithelium. Where can it be found?

• Rectangular shape with nucleus near the base of the cell

• fx: protection, secretion/absorption due to goblet cell (secretes mucous)

• May be ciliated or not

Location:

• Non-ciliated → stomach, large/small intestines,

• Ciliated → uterus, fallopian tubes, ductus deferens, small intra-pulmonary bronchi

Describe psuedostratified columnar epithelium. Where can it be found?

• Crowded columnar cells, with nucleus at different levels

• fx: moistens, warms and clean lining membranes

• May be ciliated or not

Location:

• upper respiratory tract including nasal cavity and para nasal sinuses

What type of epithelium is found in the upper respiratory tract, nasal cavity and paranasal sinuses?

Pseudostratified columnar epithelium

Describe non-keratinized stratified squamous epithelium. Where can it be found?

• Many layers of non-keratinized cells on an irregular basal layer

• Cell shape can range from cuboidal to squamous

Location:

• Buccal and alveolar mucosa

• Ventral part of tongue

• Soft palate

• Sulcular epithelium

• Esophagus

Describe keratinized stratified squamous epithelium. Where can it be found?

• Many layers of keratinized squamous cells

• fx: keratin layer is used for protection

• Create cell differentiation among its 5 layers.

Location:

• skin

• Free gingiva

• Attached gingiva

• hard palate

• dorsal side of tongue

• Lips

What are the 5 keratinized layers of epithelium (exists in epidermis)?

1. Stratum basale

2. Stratum spinosum

3. Stratum granulosum

4. Stratum lucidum

5. Stratum corneum

Describe transitional epithelium. Where can it be found?

• ranges between stratified squamous,(non keratinized) and stratified columnar epithelium

• Varying cell shapes: polyhedral, dome, flat

• Cells are soft, pliable and loosely arranged - elastic

Location:

• urinary bladder

What is the turn over time for epithelial cells?

rapid.

skin is 27 days,

oral cavity is 14 days

What are the 3 layers that make up the basement membrane?

• Lamina lucida (clear layer)

• Lamina densa (dense layer

• Reticular lamina ( contains collagen and reticular fibres)

Basal lamina is lamina lucida +densa

Basement membrane is thin, acellular and located between epithelium and connective tissue

What are the 3 major cell types found in connective tissue? What are each of their functions?

1. Fibroblasts - synthesize protein fibres and intercellular substances to sustain connective tissue

2. Macrophages - immune cells that help fight infections that may enter the connective tissue layer

3. Mast cells (basophils) - involved in allergic responses

What are the 3 types of connective tissue fibers?

1. Collagenous fibers - composed of collagen and have great tensile stregnth

2. Elastic fibers - microfilaments embedded in elastin (protein) that can stretch and return to original shape

3. Reticular fibers - composed of reticulin (protein); very fine hair like fibers that branch and form a network in the tissue

What are the 8 main types of connective tissue?

1. Loose connective tissue

2. Fibrous connective tissue

3. Adipose tissue (fat)

4. Elastic connective tissue

5. Reticular connective tissue

6. Cartilage

7. Bone

8. Hemopoetic tissue (produce RBC)

Define Loose connective tissue and its function and location(s).

• Thin membrane between organs that protects and binds them together.

• Fx: Serves as protective padding for deeper structures

• Location: beneath skin (dermis layer) and between muscles

Describe Fibrous connective tissue and its function and location(s).

• aka Dense connective tissue

• composed of strong collagenous fibers

• fx: provide support

Location:

• tendons, ligaments, eyes, skin (dermis layer)

Describe Adipose tissue and its function and location(s).

• Specialized type of loose connetive tissue that stores fat

• fx: protective cushion and heat insulation

Location:

• Hypodermis

• Certain abdominal membranes

• Oral cavity

• Around kidneys, heart and various joints

Describe Elastic connective tissue and its function and location(s).

Tissue composed mainly of elastic fibers that give tissue strength and elasticity.

fx: allows tissue to stretch

Location:

• vocal cords

• certain hollow internal organs

Describe Reticular connective tissue and its function and location(s).

Network of interwoven reticular fibers forming a supportive framework

fx+location: supports walls of blood vessels, internal organs (liver, spleen, lymphatic organs)

Describe Cartilage tissue and its function and location(s).

Intercellular material that is composed of collagen and intercellular substance. It lacks direct blood supply.

fx: provides support and decreases friction (i.e cartilage in joints)

Location:

• ends of bones in joints, in the rib cage, nose, ears, and airways

What is perichondrium?

Fibrous connective tissue sheath containing blood supply that surrounds most cartilage

What are the 2 types of cells found in cartilage?

1. Chondroblasts - produces cartilage matrix, lies internal to the perichondrium

2. Chondrocytes - mature chondroblasts that maintain the cartilage matrix

What are the small spaces surrounding chondrocytes in the cartilage matrix?

Lacuna → mature chondrocytes are located IN lacuna

What are the 3 major types of cartilage?

1. Hyaline

2. Elastic

3. Fibrocatilage

Describe Hyaline cartilage

• Most common type of cartilage in the body

• glassy, translucent appearance

• All cartilage starts as hyaline cartilage

fx: provides a smooth, low-friction surface for joint movement, supports respiratory passages, and plays a role in bone growth

Location: embryonic skeleton, growth centers, mandibular condyle

Describe Elastic cartilage

a flexible connective tissue characterized by its high content of elastic fibers and collagen fibers. Exceptional elasticity and resilience.

fx: provides flexibility, structural support in areas that its located

Location:

• external ear, auditory tube, epiglottis, parts of the larynx

Describe Fibrocartilage

Composed of a mixture of dense collagen fibers and cartilaginous tissue (hyaline).

→ always found near hyaline cartilage and will gradually merge into it.

→ Cells are enclosed in capsules of matrix giving it great tensile strength

fx: serves as shock absorber and protective cushion

Location: intervertebral discs, between bones in pelvic girdle, and TMJ

Describe bone tissue

Highly vascularized, rigid connective tissue that makes up most of the mature skeleton.

• matrix contains mineral salts and collagen

fx:

• provides internal support for body structures, and protects vital organs,

• serves as attachment site for muscles

• manufactures RBC in red bone marrow

• stores calcium and other minerals

How are the cells of bone arranged?

Concentric circles around osteonic canals

What are canaliculi? Why are they important for bone?

Canaliculi connect concentric circles (lamellae) to the osteonic cancls which allows interaction between osteocytes (mature osteoblasts).

• crucial for nutrient transport, waste removal, and communication between osteocytes, facilitating bone's ability to adapt to mechanical stress

What are osteogenic cells? Where are they located?

Stem cells that will differentiate into osteoblasts.

Located on the inner layer of periosteum.

What are osteoblasts?

Produces protein components of bone matrix that are required to build bone.

What are osteocytes?

Mature osteoblasts trapped in the bone matrix within the lacunae. They maintain the bone matrix.

What are osteoclasts?

Bone-resorbing cells located in Howship’s lacunae (shallow pits caused by resorption).

• dissolve and break down old or damaged bone cells

• make space for osteoblasts to create new bone tissue in areas that are growing or need repair

Define osteon

The unit structure in compact bone that consists of 5-20 lamellae (layers).

Define Haversian canal

Central vascular canal that runs longitudinally within the osteon surrounded by the lamellae.

• contains nerves and blood vessels

• provides nutrients for bone tissue

Define Volkmann’s canal

Similar to the Haversian canal, but it runs obliquely or at right angles from the Haversian canal.

• branches from the Haversian canal to provide innervation to more superficial bone tissue

What are lamellae?

Organized arrangements of concentric sheets (like growth rings of a tree)

Describe the Periosteum

Double layered dense connective tissue sheath.

• Outer layer contains blood vessels and nerves

• Inner layer contains osteoblasts

What are the 2 methods of Ossification (bone development)

1. Intramembranous

2. Endochondrial

Describe Intramembranous ossification. Where does it occur?

Formation of steoid (young bone) within 2 dense connective tissue sheets (intramembraneous) which eventually replaces the outer connective tissue (appositional growth)

Location:

• fontanelles (soft infant skull spots)

• maxilla

• majority of the mandible

Define appositional growth

Appositional growth refers to the increase in the diameter of bones by the addition of new bone tissue on the surface of existing bone

Describe Endochondrial ossification

Formation of osteoid (young bone) within a hyaline cartilage model.

Location: Occurs in long bones, vertebrae, ribs, head of mandible, base of skull

Define interstitial growth

Interstitial growth ossification refers to the process of bone lengthening through cartilage growth and subsequent replacement by bone tissue.

Compare and contrast Interstitial growth and Appositional growth

Compare and contrast immature and mature bone tissue.

Immature:

• First bone produced by either methods of ossification

• Indistinct lamellae

• Irregular arrangement of collagen fibers

• Many cells present

Mature:

• Replaces primary bone

• Distinct lamellae

• Very organized arrangement of collagen fibers

• Fewer cells

Describe Hemopoetic tissue

Tissue responsible for producing blood cells. It primarily resides in the bone marrow ( also includes the spleen, liver, and lymph nodes)

This tissue contains HEMATOPOETIC STEM CELLS, which differentiate into various types of blood cells, including red blood cells, white blood cells, and platelets.

*does not contain fibers

What are thrombocytes?

platelets in blood (clotting factor)

• smaller than RBC

• no nucleus

• disc shaped

What are the 6 types of white blood cells (leukocytes)?

1. Neutrophil - destroys foreign particles by phagocytosis, first to arrive at site of injury

2. Eosinophil - kills bact and helps control inflammation and allergic reactions

3. Basophil - controls inflammation and allergic reactions

4. Monocytes - contains lysosomal enzymes for destroying pathogenic particles. later stages of inflammatkion

5. Lymphocytes - Mechanism of immunity, chronic. (B cells, T cells and NK cells)

6. Mast cells - allergic response, contains heparin and histamine

What are the 3 types of Muscle tissue?

1. Skeletal

2. Smooth

3. Cardiac

Order muscle tissue from thinnest to thickest.

Myofilament → myofibril → myofiber → Musle fascicle → Muscle

Describe Skeletal muscle and its identifying characteristic(s).

Voluntary muscle meaning that it requires conscious effort to control the muscle.

• Muscle fibers (cells) are long, threadline with alternating light and dark cross markings (STRIATIONS)

• Nucleus is off to the side

Describe Smooth muscle tissue.

Involuntary, non-striated muscle cells. nucleus is located centrally.

Location:

• walls of hollow internal organs, glands, and linings of blood vessels

Describe Cardiac muscle tissue

Involuntary, striated muscle tissue found only in the heart characterized by its INTERCALATED DISCS between cells. Arranged in branched, interconnecting networks.

Draw and label a Neuron (nerve cell): Dendrites, Axon, Body, Axon terminal, Synapse

Define synapse

the site of transmission of electric nerve impulses between two nerve cells (neurons) or between a neuron and a gland or muscle cell (effector)

Define ganglion

Grouping of neuron cell bodies outside of the CNS

Compare and contrast afferent and efferent nerves.

Afferent Nerve:

• aka sensory neuron

• carries info from PNS to CNS (body to brain)

• transmits sensory information (pain, temp, tactile info)

Efferent Nerve:

• aka motor neurons

• carries info from CNS to PNS (brain to body)

• transmits motor information for controlling muscle movement