Human Anatomy Exam 1

standard anatomical position

the universal reference posture of the human body used by medical professionals and scientists to describe locations, directions, and relationships of body parts accurately

Key Characteristics:

• Body posture: Standing upright and erect with feet close together and parallel.

• Head and gaze: Head facing forward with eyes open, looking straight ahead, and mouth closed.

• Upper limbs: Arms hanging straight down at the sides of the body.

• Palms and hands: Palms facing forward with thumbs pointing away from the body, making the radius and ulna bones in the forearm parallel.

median sagital plane

the vertical plane that divides the body into equal left and right halves

horizontal/transverse plane

a horizontal plane that divides the body into upper and lower sections

parasagittal lines

a vertical line that splits the body into unequal halves; parallel to median sagittal plane

right

the right side of the specific body you’re viewing, own left as you face them

left

the left side of the specific body you’re viewing, own right as you face them

medial

towards the midline of the body

lateral

away from the midline of the body

superior/cranial

position higher up or closer to head of body

inferior/caudal

position lower or farther from head of body

proximal

closer to the point of where the limb attaches

distal

farther from the point of where the limb attaches

posterior/dorsal

towards the back of body

anterior/ventral

towards the front of body

coronal plane

vertical line that splits the body into front and back halves

dorsal vs. palmer

Dorsal: back of hand

Palmer: palm of hand

dorsal vs. plantar

Dorsal: top of foot

Plantar: bottom of foot

lingual

structures positioned towards the inner side of mouth

labial

on the outside of the mouth towards the lips

mesial vs. distal

Mesial: towards center of teeth arc

Distal: away from center of teeth arc

buccal

on or near side of cheek

occusal

structures on or near surface of teeth

deep

further inward away from surface of skin

superficial

closer to the skin or surface of the body

flexion

bending a joint to decrease the angle between two bones

extension

bending a joint to increase the angle between two bones

abduction

moving a limb away from midline of body

adduction

moving a limb towards the midline of body

protonation

rotating forearm so palm faces downwards

supination

rotating forearm so palm faces upwards

circumduction

circular rotating movement

inversion

moving sole of foot inward towards the midline

eversion

moving sole of foot outwards away from midline

plantar flexion

bending foot downwards

dorsiflexion

bending foot upwards

zygote

• formed on Days 0-1

• a single diploid cell formed when a sperm cell and an egg cell fuse during fertilization

• contains zona pollucida

zona pollucida

• clear, thick outer membrane or extracellular matrix that surrounds a mammalian egg cell

• solid, unpermeable

blastomere

• forms on Days 2-3

• a type of cell produced by the early division (cleavage) of a fertilized egg, or zygote, during the beginning stages of embryonic development

morula

• forms on Day 3

• an early-stage embryo consisting of a solid, spherical ball of 13-16 cells (called blastomeres)

blastocyst

• forms on Day 4

• an early-stage mammalian embryo consisting of a hollow ball of about 100 to 200 cells

• contains trophoblast, embryoblast (innercell mass), and blastocyst cavity

hypoblast

• forms on day 7

• an inner cell layer in the early embryo below epiblast

• cubial cells

embryonic disk

• forms on Day 8

• a flattened, two- or three-layered plate of cells in an early embryo that develops into the actual body of the fetus

• contains amnion, epiblast, hypoblast, amnionic cavity, exocoelomic membrane, & primary yolk sac

epiblast

• a primary layer of pluripotent cells in the early mammalian embryo

• forms on day 8

amnion

• a thin, tough inner membrane that surrounds and protects a developing embryo

• forms on day 8

amnionic cavity

• the fluid-filled space that surrounds and protects a developing embryo

• forms on Day 8

exocoelomic membrane

• a thin, temporary layer of cells that lines the inside of the blastocyst during early embryonic development

• hypoblast side

• forms on Day 8

extraembryonic mesoderm

• a loose layer of supportive mesenchymal tissue that forms outside the developing embryo during early gestation

• It lines and helps form critical extraembryonic envelopes like the amnion, chorion, and yolk sac.

• helps form placenta

• forms on Day 12

extraembryonic coelom

• a fluid-filled space that surrounds the early embryo and its internal sacs during development

• 
  

primary yolk sac

• a temporary structure that forms during the second week of human embryogenesis

• It develops from proliferating hypoblast cells that migrate and flatten to line the inside of the blastocyst cavity

• forms on Day 8

primitive streak

• a temporary thickened band of cells that forms along the midline of an early embryo to establish the fundamental body axes

• forms on epiblast side

• forms on day 15

prochordal plate

• a specialized group of cells at the head end of a developing animal embryo

• forms on hypoblast side

• forms on day 13

connecting stalk

• a band of extraembryonic mesoderm that links the early embryo to the chorion and later develops into the umbilical cord

• forms on Days 13-17

cloacal membrane

• a temporary, two-layered embryonic structure that covers the caudal (tail) end of the primitive digestive and urogenital tract during early development

• contains ectoderm and endoderm

• forms on Day 17

cardiogenic area

a specialized horseshoe-shaped region of embryonic tissue located near the head of an early embryo where the heart first begins to form

• forms on Days 13-17

notachord

• a flexible, rod-shaped structure found in embryos that provides skeletal support and guides central nervous system development

• forms from the primitive node

• provides crucial developmental signaling

• starts form on Day 17

mesenchymal cells

• multipotent, loosely organized embryonic cells capable of differentiating into a wide variety of connective tissues

• the foundational building blocks of the body's structural framework, giving rise to bones, cartilage, muscles, and fat

trilaminar embryo

• a three-layered embryonic structure formed during the third week of human development

• contains ectoderm, mesoderm, and endoderm

• forms on Day 17

ectoderm

the outermost primary germ layer in the embryo

• giving rise to the skin, the nervous system, and sensory organs

  • forms from epiblast

endoderm

• the innermost primary germ layer of the trilaminar embryo,

• gives rise to the lining of the digestive and respiratory systems and major internal organs

intraembryonic mesoderm

• the middle germ layer of the trilaminar embryo that develops between the ectoderm and endoderm

ultimately giving rise to the bones, muscles, circulatory system, and internal organs

extraembryonic mesoderm

a transient layer of tissue that forms outside the embryo proper during the second week of development

days 17-21 of development

• the notachord starts to form and expand

neural folds

the elevated, lateral margins of the neural plate that rise up and fuse during embryonic development

• arise from primitive streak

neural groove

• shallow, midline depression that forms on the dorsal surface of the embryo during the third week of development

• serves as the immediate precursor to the neural tube

days 20-21 of development

the neural folds + grooves on the primitive streak fuse together

neural crest

• a temporary group of versatile cells unique to vertebrate embryos that break away during neurulation to form a wide variety of tissues throughout the body

• forms on Day 21

neural tube

• a hollow embryonic structure that develops into the central nervous system, including the brain and spinal cord

• forms on day 21

surface ectoderm

• the portion of the ectoderm layer that remains on the outside of the embryo after neurulation

• forms the protective outer covering of the body and several specialized sensory and glandular structures.

paraxial mesoderm

a band of embryonic tissue running alongside the central neural tube that segments into blocks of cells called somites, which form the skeletal muscle, vertebrae, and dermis

intermediate mesoderm

a narrow band of embryonic tissue located between the paraxial mesoderm and the lateral plate mesoderm that develops into the urogenital system

lateral plate mesoderm

a layer of embryonic tissue located at the outermost edges of a vertebrate embryo that splits to form the body cavities and circulatory system

surface ectoderm gives rise to…?

• epidermis

• hair, nails

• sweat + mammary gland

• ½ of pituitary gland

• tooth enamel

• inner ear

  • lens of eye

neural tube gives rise to…?

• brain + spinal cord

• retina

  • ½ of pituitary gland

neural crest gives rise to…?

• ganglia of peripheral nervous system

• part of adrenal gland

• pigment cells

• pharyngial arches

• some soft tissues of head

notochord gives rise to…?

• nucleus pulposus of inner vertebral disks

the somites give rise to…?

• skeletal muscle

• skeleton (except skull)

• dermis (skin)

• connective tissue of the “body wall”

the intermediate mesoderm gives rise to…?

urogenital system (kidneys, gonads, etc.)

• associated ducts and glands

lateral plate mesoderm gives rise to…?

• smooth muscle of the viscera

• connective tissues of the viscera

• serous membranes (pleura, paracardium, peritoneum)

• cardiovascular + lymphnode system

• spleen

  • part of adrenal gland

the endoderm gives rise to…?

• epithelium

• trachea + bronchi

• lungs

• gastrointestinal tract

• pharynx, thyroid gland

• auditory tube

• lymphanic cavity

• tonsils +parathymal glands

extraembryonic coelom

a fluid-filled space that surrounds the early embryo and its internal sacs during development

• forms on Day 21-22

intraembryonic coelom

a horseshoe-shaped, fluid-filled cavity inside the developing embryo that eventually forms the main body cavities

• forms on Days 21-22

somatopleure

• embryonic tissue layer in vertebrate animals formed by the fusion of the outer ectoderm layer and the somatic mesoderm

  • forms on Day 21-22

splanchropleure

• embryonic tissue layer in vertebrate animals formed by the fusion of the inner endoderm layer and the somatic mesoderm

  • forms on Days 21-22

what happens on day 26 of development…?

• The endoderm fuses in on itself, forming gut tube

• surface ectoderm connects together

dorsal mesentery

a double-layered membrane of tissue that suspends the embryonic gut tube from the posterior (back) abdominal wall

ventral mesentery

a temporary double-layered membrane in an embryo that suspends the primitive gut tube from the front wall of the abdominal cavity

prochordial coelom

a temporary, specialized embryonic cavity that develops within the head mesoderm anterior (rostral) to the notochord

• forms on Day 21

septum transversum

• a thick plate of embryonic mesodermal tissue that forms the primary foundation for the central tendon of the diaphragm and helps separate the thoracic and abdominal cavities

  • forms on Day 21 of development

heart

found under prochordial coelum on day 21

• forms on Day 21

pleuroperitoneal cavity

a single, continuous body cavity found in developing embryos and many non-mammalian vertebrates that combines both the pleural (chest) and peritoneal (abdomen) spaces

• forms on Day 28+

gut tube

the primary embryonic structure formed during embryonic folding that gives rise to the entire gastrointestinal tract, stretching from the pharynx down to the anus

• forms on Day 26-28+ from endoderm folding in on itself

allantois

a sac-like extraembryonic membrane that helps developing embryos handle waste and exchange gases

• found on endoderm yolk sac on cloacal membrane side

• forms on Day 21

what key event happens on day 21 of development?

the surface ectoderm begins to fold towards the yolk sac

what happens on day 22 of development

90 degree rotation in process of ectoderm folding

what happens on day 26 of development?

• we see another 90 degree rotation

• structures have flipped orientations (ex. heart on top of prochordial coelom

• pericardial sac forms

• foregut, mid gut, and hind gut emerge

pericardial sac

a protective, double-walled, fluid-filled membrane that surrounds and anchors the heart

• forms on Day 26

foregut

the front part of the digestive tract in an embryo or the upper part of the digestive system in an adult; Esophagus, stomach, and proximal (first) part of the duodenum.

mid gut

the middle section of the embryonic alimentary canal, which develops into the distal part of the duodenum, the small intestine (jejunum and ileum), and the proximal two-thirds of the large intestine

hind gut

posterior part of the digestive tract; forms the lower portion of the primitive digestive tube during early development

dermatome

a temporary embryonic layer of cells in vertebrate embryos that gives rise to both skeletal muscle and the dermis of the skin

• lower portion of somite