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Advanced Biology Chapter 7 - Skull

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Advanced Biology. Chapter 7 - Skull. Overview. Usually consists of 22 bones 8 form the cranium 14 form the facial skeleton All bones but the lower jaw are interlocked by sutures The lower jaw (mandible) is held to the cranium by ligaments. Cranium. Encloses and protects the brain - PowerPoint PPT Presentation

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Page 1: Advanced Biology

Advanced Biology

Chapter 7 - Skull

Page 2: Advanced Biology

Overview

• Usually consists of 22 bones– 8 form the cranium– 14 form the facial skeleton

• All bones but the lower jaw are interlocked by sutures– The lower jaw (mandible) is held to the cranium

by ligaments

Page 3: Advanced Biology

Cranium

• Encloses and protects the brain• Provides attachment points for muscles that make

chewing and head movement possible• Some cranial bones contained air-filled cavities

called paranasal sinuses– These sinuses are lined with mucous membranes and are

connected to the nasal cavity by passages– Reduce the weight if the skull– Increase the intensity of the voice by serving as resonant

sound chambers

Page 4: Advanced Biology

Bones of the Cranium

Page 5: Advanced Biology

Bones of the Cranium• Frontal Bone

Page 6: Advanced Biology

Bones of the Cranium

• Frontal Bone– Forms the anterior portion of the skull above the eyes– Includes the forehead, roof of the nasal cavity, and roofs of

the orbits (bony sockets) of the eyes– Develops in two parts that are usually completely fused by

the fifth or sixth year of life– Parts:

• Supraorbital foramen (or notch)– Located on the upper margin of each orbit– Allows nerves and blood vessels to pass to the tissues of the forehead

• Frontal sinus– Located above each eye near the midline

Page 7: Advanced Biology

Bones of the Cranium• Frontal Bone

Page 8: Advanced Biology

Bones of the Cranium• Parietal Bone

Page 9: Advanced Biology

Bones of the Cranium

• Parietal Bones– Located on each side of the skull just behind the

frontal bone– Are curved and have four borders– Sutures:• Fused together along the sagittal suture• Meet the frontal bone at the coronal suture

Page 10: Advanced Biology

Bones of the Cranium• Parietal Bone

Page 11: Advanced Biology

Bones of the Cranium• Occipital Bone

Page 12: Advanced Biology

Bones of the Cranium

• Occipital Bone– Forms the back of the skull and the base of the cranium– Sutures:

• Joins the parietal bones along the lambdoid suture– Special Features:

• Foramen magnum – Located on the lower surface– Allows the inferior part of the brainstem to connect with the spinal cord

• Occipital condyles– Rounded processes– Located on each side of the foramen magnum – Articulate with the first vertebra (atlas) of the vertebral column

Page 13: Advanced Biology

Bones of the Cranium• Occipital Bone

Page 14: Advanced Biology

Bones of the Cranium• Temporal Bones

Page 15: Advanced Biology

Bones of the Cranium

• Temporal Bones– Form part of the sides and the base of the

cranium– House the internal ear structures– Sutures:• Join the parietal bones along the squamous suture

Page 16: Advanced Biology

Bones of the Cranium• Temporal Bones

Page 17: Advanced Biology

Bones of the Cranium• Temporal Bones (cont.)

– Special Features:• External acoustic meatus

– Located near the inferior margin – Leads inwards to parts of the ear

• Mastoid Process– Rounded projection – Located below each external acoustic meatus – Provides an attachment for certain muscles of the neck

• Styloid process– Long, pointed process– Located below each external acoustic meatus – anchors muscles associated with the tongue and the pharynx

• Carotid canal– Located near the mastoid process– Transmits the internal carotid artery

• Jugular foramen– Opening located between the temporal and occipital bones– Transmits the jugular vein

• Zygomatic process– Projects anteriorly from the temporal bone in the region of external auditory meatus– Joins the temporal process of the zygomatic bone to form the zygomatic arch (cheek)

Page 18: Advanced Biology

Bones of the Cranium• Temporal Bones

Page 19: Advanced Biology

Bones of the Cranium• Sphenoid Bone

Page 20: Advanced Biology

Bones of the Cranium

• Sphenoid Bone– Located in anterior portion of cranium– Consists of a central part and 2 wing-like structures that

extend laterally towards the sides of the skull– Helps form the base of the cranium, the sides of the skull,

and the floors and sides of the orbits– Special Features:

• Sella turcica– Saddle-shaped depression– Located along the midline– Houses the pituitary gland which hangs from the base of the brain by a stalk

• Sphenoidal sinuses– Lie next to each other– Separated by a bony septum that projects downward into the nasal cavity

Page 21: Advanced Biology

Bones of the Cranium

• Sphenoid Bone

Page 22: Advanced Biology

Bones of the Cranium• Ethmoid Bone

Page 23: Advanced Biology

Bones of the Cranium

• Ethmoid Bone– Located in front of the sphenoid bone– Consists of two masses (one on each side of the nasal

cavity) joined horizontally by cribriform plates (which form part of the roof of the nasal cavity)• Each cribriform plate has tiny openings called olfactory foramina

through which nerves associated with the sense of smell pass• A perpendicular plate projects downward in the midline from the

cribriform plates to form most of the nasal septum– Also forms sections of the cranial floor, orbital walls, and

nasal cavity walls

Page 24: Advanced Biology

Bones of the Cranium• Ethmoid Bone (cont.)

– Special features• Superior nasal concha and middle nasal concha

– Delicate, scroll-shaped plates– Project inward from lateral portions the ethmoid bone towards the perpendicular

plate– Support mucous membranes that line nasal cavity

» Mucous membranes moisten, warm, and filter air as it enters the respiratory tract

• Ethmoidal sinuses– Small air spaces

• Crista galli– A triangular process– Projects upward into the cranial cavity between the cribriform plates– Place of attachment for membranes that enclose the brain

Page 25: Advanced Biology

Bones of the Cranium• Ethmoid Bone

Page 26: Advanced Biology

Facial Skeleton

• Consists of 13 immovable bones and a movable lower jaw bone

• Form the basic shape of the face• Provide attachments for muscles that move

the jaw and control facial expressions

Page 27: Advanced Biology

Facial Skeleton

Page 28: Advanced Biology

Facial Skeleton• Maxillary Bones

Page 29: Advanced Biology

Facial Skeleton• Maxillary Bones

– Form the upper jaw– Contain the sockets of the upper teeth – Portions of the bones form the anterior roof of the mouth (hard pallete)

the floors of the orbits, and the sides and floor of the nasal cavity– All other immovable bones articulate with the maxillary bones– Special features:

• Maxillary sinuses– Inside the maxillae, lateral to the nasal cavity– Largest of the sinuses (extend from the floor of the orbits to the roots of the upper teeth)

• Palatine processes– Portions of the maxillary bones that fuse along the midline (median palatine suture) and

form the anterior section of the hard palate• Alveolar process

– Downward projection on the inferior border of each maxillary bone– Together, the two processes form a horseshoe shaped arch called the alveolar arch

» Teeth occupy cavities in the arch and are bound to the bony sockets by dense connective tissue

Page 30: Advanced Biology

Facial Skeleton• Maxillary Bones

Page 31: Advanced Biology

Facial Skeleton• Pallatine Bones

Page 32: Advanced Biology

Facial Skeleton

• Palatine Bones– L-shaped bones located behind the maxillae– Horizontal portions form the posterior section of

the hard plate and the floor of the nasal cavity– Perpendicular portions help form the lateral walls

of the nasal cavity

Page 33: Advanced Biology

Facial Skeleton• Pallatine Bones

Page 34: Advanced Biology

Facial Skeleton• Zygomatic Bones

Page 35: Advanced Biology

Facial Skeleton

• Zygomatic Bones– Form the prominences of the cheeks below and to

the sides of the eyes– Help form the lateral walls and the floors of the

orbits– Special features:• Temporal process

– Extends posteriorly to join the zygomatic process of a temporal bone

Page 36: Advanced Biology

Bones of the Cranium• Zygomatic Bones

Page 37: Advanced Biology

Bones of the Cranium• Lacrimal Bone

Page 38: Advanced Biology

Facial Skeleton

• Lacrimal Bones– Thin, scalelike structures located in the medial

wall of each orbit between the ethmoid bone and the maxilla

– A groove in the anterior portion of the bone leads from the orbit to the nasal cavity and provides a pathway for a channel that carried tears from the eye to the nasal cavity

Page 39: Advanced Biology

Facial Skeleton• Nasal Bones

Page 40: Advanced Biology

Facial Skeleton

• Nasal Bones– Long, thin, and nearly rectangular– Lie side by side and are fused at the midline to

form the bridge of the nose– Serve as attachments for the cartilaginous tissues

that form the shape of the nose

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Facial Skeleton• Vomer Bone

Page 42: Advanced Biology

Facial Skeleton

• Vomer Bone– Thin and flat– Located along the midline within the nasal cavity– Joins the perpendicular plate of the ethmoid bone

posteriorly to form the nasal septum

Page 43: Advanced Biology

Facial Skeleton

• Inferior Nasal Concha

Page 44: Advanced Biology

Facial Skeleton

• Inferior Nasal Conchae– Fragile, scroll-shaped bones attached to the lateral

walls of the nasal cavity– Largest of the conchae– Located below the superior and middle nasal

conchae of the ethmoid bone– Support mucous membranes within the nasal

cavity

Page 45: Advanced Biology

Facial Skeleton• Mandible

Page 46: Advanced Biology

Facial Skeleton• Mandible

– Horizontal, horseshoe shaped body with a flat ramus projecting at each end

– Special Features:• Ramus

– Divided into the mandibular condyle (posterior) and the coronoid process (anterior)» The mandibular condyles articulate with the mandibular fossae of the temporal bones» The coronoid processes provide attachments for muscles used in chewing

• Alvelolar border– Curved bar of bone on the superior border of the mandible– Contains the hollow sockets of the lower teeth

• Mandibular foramen– Opening located on the medial side of the mandible, near the center of each ramus– Admit s blood vessels and a nerve that supply the roots of the lower teeth

• Mental foramen– Opening through which branches of the blood vessels and the nerve emerge– Opens on the outside near the point of the jaw– Supply the tissues of the chin and the lower lip

Page 47: Advanced Biology

Facial Skeleton• Mandible

Page 48: Advanced Biology

Passageways of the Skull

Page 49: Advanced Biology

Infantile Skull• Soft spots:

– At birth, fibrous membranes connect the cranial bones– The area where these membranes are located are called fontanels (soft spots)– Soft spots permit molding (some movement between the bones) which assists

in movement through the birth canal– Closure of soft spots:

• The posterior fontanel usually closes about 2 months after birth• The sphenoidal fontanel usually closes at about 3 months• The mastoid fontanel usually closes near the end of the 1st year• The anterior fontanel may not close until the middle or end of the second year

• Characteristics– Small face with a prominent forehead and large orbits– Jaw and nasal cavity are small– Sinuses are incompletely formed– Frontal bone is in 2 parts– Skull bones are thin and somewhat flexible and so are easily fractured

Page 50: Advanced Biology

Infantile Skull