Human anatomy test 1.

Hypodermis/subcutaneous layer

Deep to skin layer of loose areolar and adipose connective tissue. Contains cutaneous nerves, blood vessels, receptors, sweat and sebaceous glands, and hair follicles in thin skin.

Attaches skin to underlying structures, provides thermal insulation, padding, and fat, energy storage. Not part of the skin officially. Also known as subcutaneous tissue.

The important functions of skin:

Protects from the external environment, pathogens, toxins, abrasion, solar rays, extreme temps. Also prevents water loss and entry of water.

Allows for UV light to be synthesize into calcitriol. Regulates temp with capillaries, allows sensory reception, triggers the immune system response, allows secretion and absorption.

Calcitriol

Hormone that regulates calcium and phosphate levels in the blood, being an important component in bone. Comes from UV light being converted by cholesterol into Vitamin D3, which is converted by the liver and kidneys.

Capillaries

Tiny blood vessels in the dermis that help regulate body temp. Performs vasodilation when hot and vasoconstriction when cold.

Vasodilation

A process in which when hot, the capillaries open up to allow blood flow and thus for heat to dissipate through the skin.

vasoconstriction

Process in which when cold, the capillaries close up to maintain heat in our core so we stay warm.

What is the primary cell that makes up the epidermal?

Squamous epithelial cells, aka keratinocytes

keratinocytes (aka squamous epithelial cells)

Found in all layers of the epidermis. Younger cells near the basement membrane are cuboidal. As they age, getting pushed to the apical surface, they flatten into a squamous shape while producing keratin. Upon reaching the apical surface, they are dead, no longer connected to blood vessels, but maintain structure until they eventually flake off.

Keratin

A fibrous protein produced from aging keratinocytes cells that stays inside the cell, making it tough and waterproff.

Melanocytes

Epidermal cells that produce melanin, found in the deeper, basal layer of the epidermis. Has long processes that pass melanosomes, to keratinocytes which use it as a protective shield for their nuclei.

Tactile corpuscles

Large, oval encapsulated sensory receptors found in the dermal papilla of skin where there is no hair. Found on fingertips, palms, eyelids, lips, nipples, and genitals.

Detects  discriminative touch for textures and shapes, light touch

Epidermal dendritic cells

Also known as langerhan cells, these work for the immune system. Found in the deeper layers of the epidermis, they identify pathogens and report them to other parts of the immune system.

Stratum basale

The basal layer of the epidermis, a single row of cells adjacent to the basement membrane. Has large, cuboial, keratinocytes that constantly divide, aka epidermal stem cells.

Has melanocyte cells that transfer melanosomes to keratinocytes, and tactile cells provide sensory information.

Stratum spinosum

The last layer where cells can still divide. Appearing spiky, cells form strong attachments using desmosomes w/ their neighbors. Dendritic cells check for pathogens. between stratum basale and stratum granulosum.

Maintains the epidermis’ physical strength and is a barrier to infectious and harmful agents.

Stratum granulosum

Above the stratum spinosum. Has 3-5 layers of flattened, dark, older keratinocytes that begin synthesizing keratin granules, performing keratinization. At this stage, keratinocyte’s nuclei and organelles begin to disintegrate.

Stratum lucidum

Above stratum granulosum and below stratum corneum. Is several cells thick and is found only in thick skin. Cells flatten, lack nuclei or organelles, are dead, and appear clear due to eledin proteins while they accumulate keratin.

Found only in soles of feet and palms.

Stratum Corneum

The most superficial, thickest layer of the epidermis, being up to 30 cells thick. Keratinocytes are dead, squamous, and lack nuclei, but are loaded with keratin fibers that create a strong and protective barrier. Membrane thickens with extra lipids, making it mostly waterproof, and is structurally sound with desmosomes.

How long does it take keratinocytes to reach the stratum corneum and before they finally flake off?

2 weeks, and the another 2.

Thin skin

Covers most of the body, with the epidermis having only 4 layers, around 0.1 mm thick, lacking the stratum lucidum. Is more flexible and contains many other structures, including hair follicles, sweat glands, and sebaceous (oil-producing) glands.

Thick skin

Found only one the palms of hands and soles of feet. Has all five layers and is 0.5 mm thick. Lacks hair follicles and sebaceous glands as hair and oily secretions would cause issues with walking or handling things, but has sweat glands.

The basement membrane between the epidermis and dermis:

Is not flat, but composed  of interlocking projections, epidermal ridges and dermal papillae, that appear similar to packing foam.

Papillary layer

The thin, superficial layer of the dermis made of areolar CT and blood vessels, which supplies the epidermis w/ oxygen and nutrients, extends into the dermal papilla. More touch receptors along with sensory nerve endings are also found in the dermal papilla.

Reticular dermis layer

The deepest layer of the dermis comprised mostly of dense irregular connective tissue that makes up most of the dermis. Majority cells are fibroblasts but also contains elastic fibers and thick strands of collagen fibers that extend in all directions, providing strength. Blood vessels enable thermo-regulation.

Lines of cleavage

Body-wide pattern bundles of collagen and elastic fibers. If cut, can result in gaping that takes longer to heal, if cut parallel to line, will heal quicker.

Melanin

Pigment produced by melanocytes in the epidermis and transferred to keratinocytes. Provides protection for the DNA in the cell's nucleus against UV radiation (in sunlight). Darker skinned people will have the same amount of melanocytes but produce more of this.

Carotene

A yellowish pigment with a minor influence on skin color. Is seen on the soles of feet and is converted to vitamin A by liver.

Hemoglobin

found in red blood cells can affect skin color. When skin gets "flushed" due to the vasodilation of dermal blood vessels, the red blood pigment gives the skin that ruddy skin tone.

Nails

modifications of the stratum corneum that protect the tips of the fingers and toes.

Hair

Functions as protection from sun (scalp) and dust and other particles (nostrils and eyelashes).

Adults produce two types: vellus grows over most parts of the body, terminal hair grows on the scalp, eyebrows, eyelashes, axillary, pubic regions, and male faces (beards).

The 3 regions of hair

The shaft is the external portion.

The root is most of the internal portion.

The bulb is the swelling at the base in the dermis that contains dividing cells.

Hair follicle

a supportive tube in the dermis/hypodermis that surrounds the hair bulb and root made of two coats, an inner, epidermic, epithelial sheath and an outer, dermic CT sheath. Is associated w/ a sebaceous gland.

Erector/arrector pili muscle

 Bundle of smooth muscle fibers attached to the follicle. This small smooth muscle is stimulated by fear, cold, and other emotions. When contracted, this causes goosebumps.

Merocrine sweat glands

most common and widespread skin gland, with there being 3-4 million all over the body. Especially on the palms, soles, and forehead.

Has a coiled tubular section in the dermis, a secretory part composed of simple cuboidal epithelium, and a duct that takes secretions to the sweat pores on the skin’s surface.

Produces sweat which have small amounts of cellular waste products and antibacterial compounds. Functions in thermo-regulation, secreting sweat when hot. Also known as eccrine sweat glands.

Apocrine sweat glands

glands restricted to the axillary (armpit), anal and pubic regions, and around the nipples. Has a coiled tubular region with large lumen (bigger than the merocrine gland’s) in the dermis, and their duct empties into a hair follical superficial to the opening of a sebaceous gland duct.

Produces sweat, as well as proteins  and lipids which create odor when broken down by bacteria. Is not active until puberty

Sebaceous oil glands

A holocrine gland w/ a secretory part in the dermis and ducts that open into hair follicles or the skin’s surface. Cells disintegrate to release their secretions, an oily substance, sebum, which lubricates the skin, waterproofs hair shaft, and stops bacterial growth, into the hair follicle. Partially active in childhood and fully activate after puberty. Not found on palms or soles.

Fibrosis

In which damaged tissue is replaced by scar tissue, restoring structural integrity, however the original damaged tissue’s function is not restored.

Regeneration

When a damaged tissue is not only repaired, but it’s full, original function is restored

How is skin repaired?

Damaged blood vessels leak blood that coagulates and clots, pulling the wound’s edges closer while leukocytes clean the area. Neutrophils hunt down bacteria while macrophages engulf damaged cells and other debris.

How does fibroblasts play a role in repairing skin through fibrosis?

They divide, replacing lost cells and produce new matrix w/ collagen and elastic fibers to form a new, granulation tissue. Macrophages engulf debris and break down clooted blood while new blood vessels grow. Granulation tissue is replaced by tough scar tissue and the scab falls off as new epidermis emerges.

Muscle tissues

Unique tissue that is contractile, meaning muscle can contract with force, and excitable, meaning it responds to electrical stimulation. Moves with the skeleton and organ walls.

Skeletal Muscle

moves skeleton and helps with thermo-regulation. Primarily attached to our bones, but can attach to skin or form sphincters. Can be moved voluntary without a nerve telling them.

Cells are large and long, containing multiple nuclei and therefore are called “fibers”. These fibers don’t branch having a striated, stripy appearance.

Cardiac muscle

Muscle exclusive to the heart, providing the pumping mechanism for blood. Involuntary, can’t be consciously controlled by us and doesn’t need nerves, functioning on their own.

Has small, striated, short cells that branch, connected by interlacated discs, structures that allow cells to communicate.

Smooth muscle

found in the walls of our internal, hollow organs (for example, stomach, urinary bladder, blood vessels, etc.) and few specialized locations (inside the eye and attached hairs in the skin).

Cells are small, thick in the middle and tapered at the ends, and are not striated. Considered involuntary, can’t be consciously controlled.

Nervous Tissue

Tissue found in nerves, the brain, and spinal cord. Sends electrical impulses, being conductive, and processes information. Has two cell types: neurons and glial cells.

Neurons

The longest cells in the body that also transmit electrical impulses. They have a cell body (neurosoma) and numerous extensions called dendrites that receive incoming information. Some have very long processes known as axon that send outgoing impulses long distances.

Glial cells

Also known as neuroglia, supports neurons by providing nourishment and guidance during development. Regulating local environments, and protecting the neurons. Even though they are relatively small cells, they far outnumber the neurons.

Body membranes

Simple organs that are a combination of just a layer of epithelial tissue supported by connective tissue.

Lumen

The hollow part inside the organ. Plenty found in tracts and blood vessels.

Mucous membrane

Lines the inside of the stomach, and major tracts; the respiratory tract, urinary tract, digestive tract, and reproductive tract. Provides protection, secretory functions, most producing a layer of mucus, and sometimes absorption.

Apical surface is a layer of epithelial columnar tissue and areolar CT. Underneath is a supporting layer of dense, irregular CT that contains blood vessels and nervous tissue that regulate stomach secretion.

How does smooth muscle appear?

as three layers between the serous membrane and mucous membrane, but is actually all the same material, just in different orientations. Has nervous tissue that regulates muscle contractions.

Where is the serous membrane found in regards to the stomach?

Outside of the stomach.

The structure of body membranes

The apical surface has a layer of epithelial tissue over a basement membrane which attaches the basal surface of the epithelium to connective tissue.

Basement membrane

A layer of sticky molecules that attaches the basal surface to deeper connective tissue.

Serous membranes

double-layered body membranes that line the inside of the ventral/anterior cavity, protecting and covering the organs in the cavity. Contains a simple squamous epithelium called mesothelium.

The layer that lines the inside of the cavity is called the parietal layer, the layer that covers each organ is the visceral layer.

Between the two layers is a serous cavity filled with lubricative serous fluid, which allows organs to move in the ventral cavity.

Has three types: pleura, pericardium, and paritoneum.

Cutaneous membrane

Body membrane that forms a protective cover on the outside of the body, AKA skin. Is the largest membrane (and organ) in the body. Part of the integumentary system

Epidermis

Thick epithelial part of skin made of keratinized stratified squamous epithelium that acts as a physical barrier. Avascular, lacking blood vessels, but has receptors, nervous tissue, and exocrine gland ducts. Contains stem cells, melanocytes, and dendritic cells.

Dermis

The connective tissue, middle, thicker part of skin. Contains sweat and sebaceous glands, blood vessels, hair follicles, and receptors. Supports the epidermis, strengthens skin w/ collagen & elastin, and regulates body temp.

Is made up of two layers: a superficial, thin papillary layer made of areolar CT, and a thicker, reticular layer made of dense irregular connective tissue.

Synovial membranes

Body membrane that lines most joints. Lacks the epithelial layer and basement membrane, but does produce a type of fluid (synovial) that reduces friction.

Hypertrophy

when tissue gets bigger, but the number of cells stays the same. Weight training increases muscle size but does not actually create more muscle cells, the existing cells just get bigger. Adipose cells tend to increase in size instead of number.

Hyperplasia

when the number of cells increases. This occurs during pregnancy as the uterus enlarges, and is the main growth mechanism in childhood..

Atrophy

 when a tissue shrinks in size or in cell number. Skeletal muscles will get smaller if they are not used.

Metaplasia

when a tissue transforms into a different tissue.

Dysplasia

when a tissue develops abnormally. If that tissue starts to grow uncontrollably, this creates cancerous tissue (tumor), a situation called neoplasia.

Necrosis

when tissue dies, usually after damage or disease. Another form of cell death is called apoptosis, but this action is intentional and beneficial. During growth, unneeded extra cells die using apoptosis. Infected cells are often sacrificed by our immune systems in this manner.

How can tissues change?

Through hypertrophy, hyperplasia, atrophy, metaplasia, dysplasia, and necrosis

As we age, epithelial tissues _____, while muscle and nervous tissue ___

thin out; begin to atrophy

As we age, connective tissues ______.

Make fewer elastic fibers, making them not stretch and rebound as well, causing stiffness, which can cause blood pressure to rise in arteries. Also makes less collagen, losing strength, bones become brittle and skin thins.

Connective tissue (CT)

the most common and widespread basic tissue. Is found everywhere in the body, providing physical support and protection, strength, storage, and fills in spaces.

Also "connects" different areas, helping to transport substances and cells around the body. All are related, sharing a common embryonic origin. Composed of just cells, resident and wandering, and a matrix.

The resident cells of connective tissue

Mesenchymal cell, macrophage, adipocyte, and fibroblast.

Fibroblasts

the most common cell found in connective tissue (proper). Produces the extracellular matrix (fibers and ground substance).

Adipocytes

A resident cell in connective tissue that is filled with lipids (triglycerides).

These common cells are used for cushioning, insulation, and to store energy.

Macrophages 

A resident cell in CT that cleans up cell debris and potential pathogens, disease-causing organisms, using phagocytosis.

Some connective tissue have specialized types unique to it: chondrocytes, osteocytes, and erythrocytes.

chondrocytes

A macrophage found in cartliage.

osteocytes

A macrophage found in bone.

erythrocytes

A macrophage, a resident cell that cleans up cell debris and pathogens from connective tissue, found in blood.

Wander cells

CT cells that are not fixed in place. Includes all leukocytes, white blood cells, neutrophils (which hunt down bacteria) and dendritic cells (which communicate with other immune system cells).

Extracellular Matrix (ECM)

The material between cells, composed of protein fibers and ground substance. Is one of the two components in connective tissue.

Protein fibers

provides strength and a framework for cells to maintain their position. Is a component of the ECM. There are three types in connective tissue: Collagen fibers, elastic fibers, and reticular fibers.

Collagen fibers

are the most common fiber and protein in the body. Collagen provides support and strength; they are flexible but do not stretch. Are the major components of skin and bone.

Elastic fibers

are branched fibers made out of a protein called elastin. They can stretch and recoil (unlike collagen), and are found in skin, lungs, and some blood vessels.

Reticular fibers

Fibers similar to collagen, but is a branching, interlocking network. This arrangement is not that strong, but it’s great for housing wandering cells. it is found in organs that are part of the immune system (lymph nodes and spleen) and some glands.

Ground substance

the non-fibrous component of matrix. In many tissues, is mostly water (especially blood), along with some proteins, and carbohydrates.

In the supporting connective tissues, contains extra components that create a semisolid (in cartilage) or even a hard solid (bone).

Epithelial versus connective tissue

CT:

• Is mostly ECM w/ few cells

• Has blood vessels, and can regenerate at varying degrees.

Epithelial tissue:

• Mostly cells w/ little ECM

• No blood vessels but all are good at regeneration

The three categories of connective tissue;

Connective tissue “proper”, supporting connective tissue, and fluid connective tissues.

Connective tissue "proper"

General CT w/ a soft matrix but plenty of protein fibers.

The six subtypes are divided into two groups depending on the relative proportions of cells, ground substance, and especially protein fibers.

Loose proper connective tissue has few protein fibers, dense proper connective tissue is loaded with protein fibers.

Loose “proper” connective tissue

proper CT w/ abundance in ECM, having lots of ground substance and few fibers scattered throughout. There are cells, but they can be spread out (and not in contact with other cells). Has lots of blood vessels.

Has three types: Areolar, adipose, and reticular connective tissue.

dense proper connective tissue

CT loaded with protein fibers, containing few cells and ground substance. Is usually found in areas where strength is needed. Has three subtypes: dense regular, dense irregular, and elastic.

Elastic Dense proper connective tissue

Dense proper CT composed of densely packed elastic fibers allowing stretch and recoil as well as providing strength. Is only found in a few locations including large blood vessels (arteries) and vocal cords.

Note- don’t confuse for elastic cartilage!

Periosteum

is a covering around bones made out of dense irregular connective tissue.

Protective capsules

Outer layers of dense irregular connective tissue that cover many organs (liver, kidneys, spleen, lymph nodes etc.)

Irregular Dense “proper” connective tissue

Dense proper CT composed mostly of collagen fibers that run in all direction, creating a strong sheet of tissue.

Found in the dermis and sheaths of tissue that surround, support, and contain several organs (muscles, nerves, cartilage, and bones). Makes up the periosteum, which covers bone, and protective capsules.

Regular Dense “proper” connective tissue

Dense proper CT composed mostly of collagen fibers arranged in a regular, parallel pattern that is exceptionally strong in one direction.

The few fibroblasts present make the protein fibers and small amounts of ground substance.

There are few blood vessels present, so repair is slow.

Only found in two structures: tendons (joining muscles to bone) and ligaments (attaching bones to other bones).

Supporting connective tissues

have lots of fibers, specialized cells, and either a semisolid (cartilage) or a solid (bone) extracellular matrix.

Bone tissue

A type of supporting connective tissue with a solid ECM w/ specialized cells, osteocytes, located in tiny open spaces (lacunae). Collagen fibers provide strength, and additional compounds in the matrix add hardness. Has plenty of blood vessels, can repair itself. Makes up majority of bone

Fibrocartilage

Cartilage supporting CT with thick bundles of collagen fibers making it able to resist compression and absorb shock.

Is found as discs in between vertebrae (in the spinal column), parts of the knee, and in some joints.

Bones are made up primarily by _________, but also contain ___, ____, and ___.

Bone connective tissue; other connective tissues, nervous tissue, and some epithelial tissue

Spongy bone

A type of bone supporting CT made up of a network of small spikes and plates.

Is located on the inside of bones, and bone marrow is found in between the bone tissue.

Compact bone

A bone supporting CT that appears solid (there are some channels) and has a very precise arrangement of bone tissue cylinders (called osteons) that increase strength. Forms the outer layer of each bone.