Lab Ex 7/8 Quiz - Integumentary and Skeletal System

terms/concepts specifically for quiz, pulled from Ch 5 deck

Integumentary System components

The organ system consisting of the skin, sudoriferous (sweat) glands, sebaceous (oil) glands, hairs, nails, and subcutaneous tissue.

3 main layers of the skin and their composition

1. Epidermis - outermost protective shield of the body, consisting of avascular epithelial tissue (stratified squamous)

2. Dermis - middle layer, under epidermis. Makes up the bulk of the skin, composed mostly of dense connective tissue. Provides structural support and houses blood vessels and nerves (aka is vascular).

3. Hypodermis - aka subcutaneous, composed mostly of adipose and some areolar connective tissue that loosely anchors skin to underlying muscles, absorbs shock, and provides insulation.

4 Skin Cell Types and Functions

1. Keratinocytes - most common cell type found throughout. Produces fibrous keratin, providing protective properties

2. Melanocytes - cells that produce the pigment melanin, which gives skin its color and helps protect against UV radiation. Located in the basal layer of the epidermis.

3. Dendritic Cells - aka Langerhans cells; star-shaped macrophages which play a role in the immune response by detecting foreign substances and initiating defense against pathogens. Located in the stratum basale layer of the epidermis

4. Tactile Cells - aka Merkel cells; sensory receptors located in the epidermis that are involved in the sensation of touch. They are associated with nerve endings and help detect pressure and texture.

5 layers of the epidermis in order + function/purpose

The five layers of the epidermis, from most superficial to deepest are:

1. Stratum Corneum - The “horney” outer layer of the epidermis, consisting of 20 to 30 rows of flat, anucleated, keratinized dead cells, accounting for three-quarters of epidermal thickness. Acts as the primary physical shield against bacteria, chemicals, and scrapes. It locks in moisture to keep the body hydrated before these dead cells shed.

2. Stratum Lucidum - The clear layer of the epidermis found only in thick skin, consisting of a thin translucent band of two to three rows of clear, flat, dead keratinocytes. It gives extra protection against friction and damage in high-wear areas.

3. Stratum Granulosum - The “granular” layer of the epidermis, 1 to 5 layers of flattened cells; where nuclei and organelles disintegrate, and keratinization begins. Cytoplasm full of lamellar granules (release lipids for waterproofing) and keratohyaline granules (hard keratin protein).

4. Stratum Spinosum - The “prickly” layer of the epidermis, several cell layers thick, containing keratinocytes with a web-like system of intermediate pre-keratin filaments attached to desmosomes. Provides skin strength and flexibility. It contains immune cells (Langerhans cells) that fight off infections and foreign germs

5. Stratum Basale - firmly attached to the dermis and consisting of a single row of actively mitotic stem cells; also known as stratum germinativum. Contains active stem cells that constantly divide to produce new skin cells (keratinocytes)

Layers of the Dermis + composition/function

The dermis has two layers:

1. Papillary Layer - the upper layer consisting of loose areolar connective tissue, containing blood vessels, lymphatics, and dermal papillae -nourishes the epidermis and supports the skin's flexibility and structure.

2. Reticular Layer - the deeper layer that contains dense irregular connective tissue with thick, interwoven bundles of collagen fibers and elastic fibers, providing strength, elasticity, and housing larger blood vessels, sweat and sebaceous glands, and hair follicles. Makes up approximately 80% of dermal thickness.

Definition and function of dermal papillae

Definition: Fingerlike projections from the superficial region of the dermis into the epidermis that contain capillary loops, free nerve endings, and tactile corpuscles (Meissner's corpuscles).

Function: They form an uneven, interlocking boundary with the epidermis that stops the skin layers from sliding apart or shearing under pressure, while feeding the epidermis with oxygen and vital nutrients and enhancing sensory perception by increasing surface area.

Lamellar (pacinian) corpuscles vs Meissner’s (tactile) corpuscles

Lamellar corpuscles: Large sensory receptors located deeper in the dermis (reticular layer) that respond to deep pressure and vibration. Shaped like a large, concentric "onion bulb" with many layers of specialized cells surrounding a single nerve fiber.

Meissner’s corpuscles: Small, specialized mechanoreceptors located in the upper dermis that detect light touch. Shaped like a stacked "coin stack" of flattened supporting cells with spiraling nerve endings

How are fingerprints formed?

By the unique patterns of ridges and grooves (aka friction ridges) created by the dermal papillae in the skin, which are influenced by genetics and fetal development, resulting in distinct patterns for every individual.

Categories of cutaneous glands

1. Sebaceous (oil) glands - Widely distributed holocrine oil glands (absent on palms and soles) that secrete sebum into hair follicles.

2. Sudoriferous (sweat) glands - Sweat glands that function in controlling body temperature; present on all skin surfaces except nipples and parts of external genitalia.

Types of sweat glands

1. Eccrine glands - The most numerous sweat glands, abundant on palms, soles, and forehead, whose ducts connect to pores on the skin surface to release sweat for thermoregulation. Produce a clear, watery fluid made of water and electrolytes (salt). This sweat is generally odorless.

2. Apocrine glands - Large sweat glands located mostly in axillary and anogenital areas that secrete viscous milky or yellowish sweat containing fatty substances and proteins into hair follicles (remain dormant until puberty). Bacteria on the skin break down this fluid, which causes body odor.

Axial bones

Bones located along the body's vertical axis (including the skull, vertebral column, and rib cage) that carry other body parts, provide support, and protect organs.

Appendicular bones

Bones that make up the limbs and the girdles (pelvis and shoulder blades) that attach limbs to the axial skeleton, enabling movement.

Compact (cortical) bone vs Spongy bone

Compact bone is the dense, smooth-looking external layer of bone tissue found in the shaft of long bones, responsible for strength and support. Houses yellow bone marrow.

Spongy bone, found mainly at the ends of long bones, is a porous, honeycomb-like internal layer of bone constructed of trabeculae. Houses red bone marrow.

Trabeculae

Tiny cross-hatching structural supports inside spongy bone - helps resist stress and houses bone marrow.

Red bone marrow

Bone marrow tissue responsible for producing new blood cells (hematopoiesis).

Yellow bone marrow

Bone marrow tissue that stores energy in the form of fat.

Epiphyses

The flared ends of long bones that contain spongy bone and red bone marrow. Identified as proximal or distal depending on which end is being examined.

Diaphysis

The main shaft of a long bone that surrounds the central hollow medullary cavity.

Medullary cavity

The hollow cavity inside the diaphysis of long bones filled with yellow bone marrow.

Osteons - definition, structure, and function

Definition: Cylindrical, weight-bearing structural units of bone that run parallel to the bone's long axis. Also known as the Haversian system.

Structure: Made of lamellae, lacunae, and osteocytes arranged around a central canal that contains blood vessels and nerves.

Function: Provide support and strength to the bone tissue and facilitate nutrient transport.

Central canals

Tunnels running through the length of each osteon that contain blood vessels, nerves, and lymphatic vessels - facilitate communication and nutrient exchange within the bone tissue.

Also called the Haversian canal

Lamellae - definition and 3 types/location+function

Thin, plate-like sheet of tissue arranged in layers in the bone matrix.

• Concentric lamellae - arranged in concentric tube-like layers, form the rings of an osteon, like circular rings nested inside one another. Contain collagen fibers running in alternating directions to resist twisting stress/torsion.

• interstitial lamellae - fill the spaces between complete, functional osteons, providing structural continuity and strength. Byproduct of bone remodeling, where osteoclasts resorbed part of an old osteon, and osteoblasts built a new one over it

• Circumferential lamellae - Large parallel sheets encircling the entire bone, providing additional strength and support. Lines the outer surface (under periosteum) and inner surface (under endosteum).

Lacunae

Tiny oblong chambers tucked between concentric lamellae layers that house osteocytes.

Osteocytes

Mature bone cells housed in lacunae that monitor and maintain the bone matrix and trigger bone remodeling. (example: detection of bone fracture)

Canaliculi

Tiny microchannels that radiate outward from each lacuna to connect neighboring lacunae and blood vessel canals. This network allows osteocytes to share nutrients, oxygen, and waste products despite the dense, hard surrounding bone.

Periosteum

A fibrous membrane of dense irregular connective tissue covering the outer surface of the long bone shaft.

Layers of periosteum:

• outer fibrous layer - protect the bone and contain blood vessels, lymphatic vessels, and sensory nerves

• inner cambium (osteogenic) layer - responsible for bone growth and repair, contains osteoblasts and osteoprogenitor cells

Perforating fibers

Collagen fibers of the periosteum that firmly anchor the periosteum to the underlying compact bone matrix. Originate in the fibrous outer layer and penetrate deeply into the outer circumferential lamellae of the bone

Also called Sharpey’s fibers

Articular cartilages

covers the epiphysis at movable joints to minimize friction

Epiphyseal plate vs Epiphyseal line

Plate: A thin layer of hyaline cartilage in a growing long bone that enables longitudinal growth.

Line: The thin, barely discernible remnant of the epiphyseal plate present in adult bones after growth stops.

Endosteum

A delicate vascular membrane lining the medullary cavity, covering trabeculae of spongy bone, and lining central/perforating canals.

Contains bone-lining cells, active osteoblasts (which build bone), and osteoclasts (which break down bone)